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Embolic and thrombotic events after COVID-19 vaccination

August 23, 2023

"VITT" redirects here. For other uses, see VITT (disambiguation).

Post-vaccination embolic and thrombotic events, termed vaccine-induced immune thrombotic thrombocytopenia (VITT),[1][2][3][4][5] vaccine-induced prothrombotic immune thrombocytopenia (VIPIT),[6] thrombosis with thrombocytopenia syndrome (TTS),[7][4][5] vaccine-induced immune thrombocytopenia and thrombosis (VITT),[5] or vaccine-associated thrombotic thrombocytopenia (VATT),[5] are rare types of blood clotting syndromes that were initially observed in a number of people who had previously received the Oxford–AstraZeneca COVID‑19 vaccine (AZD1222)[a] during the COVID‑19 pandemic.[6][12] It was subsequently also described in the Janssen COVID‑19 vaccine (Johnson & Johnson) leading to suspension of its use until its safety had been reassessed.[13] On 5 May 2022 the FDA posted a bulletin limiting the use of the Janssen Vaccine to very specific cases due to further reassesment of the risks of TTS, although the FDA also stated in the same bulletin that the benefits of the vaccine outweigh the risks.[14]

In April 2021, AstraZeneca and the European Medicines Agency (EMA) updated their information for healthcare professionals about AZD1222, saying it is "considered plausible" that there is a causal relationship between the vaccination and the occurrence of thrombosis in combination with thrombocytopenia and that, "although such adverse reactions are very rare, they exceeded what would be expected in the general population".[12][15][16][17]

Signs and symptoms

The thrombosis events associated with the COVID‑19 vaccine may occur 4–28 days after its administration and mainly affects women under 55.[6][2][18] Several relatively unusual types of thrombosis were specifically reported to be occurring in those with the reaction: cerebral venous sinus thrombosis and thrombosis of the splanchnic veins.[19][20] Cerebral venous sinus thrombosis may cause severe headache, stroke-like symptoms (weakness of a limb and/or facial muscles), seizures and coma.[21] Splanchnic vein thrombosis may cause abdominal pain, accumulation of fluid in the abdominal cavity, and gastrointestinal bleeding.[22][23]

Other forms of thrombosis, such as the more common pulmonary embolism, may also occur. Arterial thrombosis has also been reported.[24] The low platelet count may manifest as petechia (tiny blood spots under the skin) beyond the site of the injection.[19]

Disseminated intravascular coagulation (DIC), diffuse formation of blood clots throughout the blood vessels of the body, has been reported as part of the syndrome.[25] DIC may cause a range of symptoms, including abnormal bleeding, breathlessness, chest pain, neurological symptoms, low blood pressure, or swelling.[26]

COVID‑19 vaccines have some adverse effects that are listed as common in the two or three days following vaccination which are usually mild and temporary.[19]

Causes

The rare simultaneous occurrence of thrombocytopenia (low blood platelets) with blood clots after vaccination raised the original concern about this condition.[citation needed] In many cases where acute thrombosis and thrombocytopenia have been found together after COVID‑19 vaccination, an antibody against platelet factor 4 has been identified.[1] This phenomenon is mostly encountered in some people who have been administered heparin, but none of the reported cases had received heparin.[1] More rarely, this phenomenon had previously been described as an autoimmune phenomenon in people who had not been exposed to heparin.[27] One striking feature of thrombocytopenia in the presence of anti-PF4 antibodies is the propensity of some to develop thrombosis, a phenomenon called heparin-induced thrombocytopenia if heparin is involved.[28]

Thrombocytopenia is generally a common symptom after or during many viral infections,[29] and it "has been consistently reported" after intravenous administration of adenoviral gene transfer vectors,[30] although its mechanisms are not yet clear.

There is no confirmed causal link to the syndrome and any COVID‑19 vaccination,[citation needed] however EMA is conducting investigations into AZD1222 and the Janssen COVID‑19 vaccine (Johnson & Johnson) for possible causal links.[31]

On 7 April 2021, the EMA noted one "plausible explanation" for the combination of blood clots and low blood platelets is "an immune response, leading to a condition similar to one seen sometimes in people treated with heparin", that is heparin induced thrombocytopenia (HIT).[19]

Diagnosis

In the United Kingdom, professional societies led by the Royal College of Emergency Medicine have issued a guideline for suspected cases. Someone presenting with concerning symptoms between five and 28 days after administration of the vaccine is assessed for a possible thrombotic complication, with a full blood count (which includes a platelet count) as the initial investigation. If the platelet count is decreased, determination of the D-dimer and fibrinogen levels may be performed, with hematology expert advice recommended if these are elevated above specific cut offs.[24]

Management

Guidelines from professional societies recommend treatment with alternative anticoagulants instead of heparin, as there is a possibility that it may aggravate the phenomenon.[32][33] Alternative options as the directly acting oral anticoagulants (DOACs), argatroban, fondaparinux or danaparoid depending on the circumstances.[32] Platelet transfusion is discouraged, as this too may aggravate thrombosis.[32] UK guidelines by the British Society for Haematology recommend the administration of intravenous immunoglobulin (IVIG) to reduce levels of the pathogenic antibody.[32] Low fibrinogen levels may require correction with fibrinogen concentrate or cryoprecipitate.[32]

Epidemiology

The Paul Ehrlich Institute has recorded 31 cerebral venous sinus thromboses (CVST) and nine deaths out of 2.7 million vaccinated in Germany with the AZD1222.[34] On 2 April 2021, the UK's Medicines and Healthcare products Regulatory Agency reported 22 cases of CVST and a further eight cases of clotting problems both associated with a low level of blood platelets following a "rigorous review" of its Yellow Card reporting. The institute also reported finding no events of this type which occurred after vaccination with the Pfizer–BioNTech COVID‑19 vaccine.[35] The EMA had earlier said that a link between certain very rare blood clots and the AstraZeneca vaccine is "not proven, but is possible".[35]

Observations in Germany of these rare events seemed to relate mostly women aged under 55. However, because Germany had previously restricted AZD1222 to under 65s, the population vaccinated there with AZD1222 is comparatively younger, and consequently contained a higher proportion of women taking the contraceptive pill. As CVSTs are more likely in women using hormonal contraceptives, this inherent risk factor may be an influence on the reported preponderance of women experiencing these events following vaccination.[34][1] The UK, in contrast, has applied its Pfizer and AZD1222 vaccines generally to older groups first, then by decreasing age.[34]

The UK Medicines and Healthcare products Regulatory Agency (MHRA) reporting regards AZD1222 to 3 November 2021, recording 73 deaths out of 425 cases (17%) in the context of 24.9 million first doses administered.[36][37]

Regulatory status

According to the European Medicines Agency (EMA), as of 28 March 2021, the reported number of cases of embolic and thrombotic events after vaccination is lower than the rate of such events in the general population overall. However, the specific syndrome - of embolic and thrombotic events in combination with low levels of blood platelets - presenting in post-vaccination cases raised the possibility of an association between the vaccine and the relatively rare syndrome. The EMA also said that there is no proof that these events are caused by the vaccines, but that the possibility could not yet be ruled out completely.[12] Accordingly, the EMA advised that people who received the vaccine and experienced symptoms suggestive of thrombosis, including shortness of breath, blurred vision and severe or persistent headache, should seek medical attention.[12]

In a press briefing on 7 April 2021,[38][39] Emer Cooke, the executive director of the European Medicines Agency (EMA) began by stating "Our safety committee, the Pharmacovigilance Risk Assessment Committee (PRAC) of the European Medicines Agency, has confirmed that the benefits of the AstraZeneca vaccine in preventing COVID‑19 overall outweigh the risks of side effects. COVID‑19 is a very serious disease with high hospitalization and death rates and every day COVID is still causing thousands of deaths across the EU. This vaccine has proven to be highly effective, it prevents severe disease and hospitalization, and it is saving lives. Vaccination is extremely important in helping us in the fight against COVID‑19 and we need to use the vaccines we have to protect us from the devastating effects".[40] She went on to say "The PRAC after a very in-depth analysis has concluded that the reported cases of unusual blood clotting following vaccination with the AstraZeneca vaccine should be listed as possible side effects of the vaccine".[41] At the same briefing Dr. Samina Strauss of PRAC confirmed "our conclusion is that these clotting disorders are very rare side effects of the vaccine".[42]

The UK Medicines and Healthcare products Regulatory Agency (MHRA) held a news conference on 7 April 2021, and while there is no proof that the AZD1222 vaccination caused the rare blood clots, they indicated the possibility of a link is getting stronger.[43] The UK is to offer under 30s alternative vaccines.[43] The reasoning is because in the 20-29 age range the benefits to individual of vaccination were less as their likelihood of harm from COVID‑19 is less and closer to the potential risk of harm from the vaccine (at a medium exposure risk with COVID‑19 infection cases running at a rate of 60 per 100,000).[44][43] For higher age groups the benefit to risk ratio increased.[43]

Also on 7 April 2021, an interim statement from the WHO said its advisory body, GACVS, found any "causal relationship" between the rare blood clot cases and AZD1222 to be "plausible but is not confirmed".[45]

On 20 April 2021, the safety committee of the EMA (PRAC) found a "possible link to very rare cases of unusual blood clots with low blood platelets" for the Johnson & Johnson Janssen vaccine; and required that these rare events, similar to those noted for AZD1222, should be listed as a very rare side effect. The EMA states the overall risk-benefit for the Janssen vaccine remains positive.[46]

On 16 December 2021, the US Centers for Disease Control and Prevention (CDC) recommended the Moderna and Pfizer-BioNTech vaccines should be preferred over the Janssen vaccine, following growing concerns about rare blood clots.[47][48] Janssen should still be offered to people who specifically request it.[49]

History

Organizations

Global vaccine safety comes under the remit of the World Health Organization (WHO), and in particular its Global Advisory Committee on Vaccine Safety (GAVCS). Other drug regulatory agencies significantly involved include:[citation needed]

Syndrome identification

A number of COVID‑19 vaccines began to become approved and available at scale in December 2020, with vaccinations beginning to ramp up at scale from the beginning of 2021, among them the Oxford–AstraZeneca COVID‑19 vaccine, based on an adenovirus vector and internally termed AZD1222.[citation needed]

On 11 March 2021, the EMA issued a statement noting Denmark had suspended AZD1222 vaccinations due to a vaccinated patient dying with blood clots. While noting there had been reports of other vaccinated people having blood clots and that its safety committee is already reviewing such cases, the number of thromboembolic events in vaccinated people is no higher than in the general population.[51]

The World Health Organization (WHO) Global Advisory Committee on Vaccine Safety on 19 March 2021, issued a statement relating to safety signals related to AZD1222 relating to thromboembolic events and thrombocytopenia following review of available data and conclusions included that AZD1222 "a positive benefit-risk profile, with tremendous potential to prevent infections and reduce deaths across the world".[52]

In its safety update of 29 March 2021, the EMA indicated it had initiated investigations into the very rare cases of specific embolic and thrombotic events in combination with thrombocytopenia (low levels of blood platelets) and related bleeding including disseminated intravascular coagulation and cerebral venous sinus thrombosis (CVST), noting any link with AZD1222 is not proven but could not be excluded.[12] The EMA also initiated an assessment for all COVID‑19 vaccines used in the EU for immune thrombocytopenia (ITP), described as low blood platelet levels that could lead to bruising and bleeding, as a possible side effect, whilst also stating that up to this point no link with any COVID‑19 had been established.[12]

On 7 April 2021, the EMA determined that unusual blood clots with low blood platelets should be listed as very rare side effects of AZD1222, with WHO and UK EHRA issuing generally similar statements on the same day. None of the agencies found a confirmed causal link between the vaccine and these incidents at the time, but were listing them out of an abundance of caution.[19][43][45]

A highlight of minutes of the EMA's Pharmacovigilance Risk Assessment Committee (PRAC) concluding 9 April 2021, indicating they also were investigating four cases of unusual blood clots with low blood platelets, including one death, amongst people who had taken the Janssen COVID‑19 vaccine. The Janssen vaccine is approved but not yet deployed in the EU, though vaccinations are in progress in the US. PRAC has determined that it is not clear if there is a causal association. Should regulatory action prove necessary, PRAC have indicated the likely outcome would be an update to product information characteristics.[53]

Vaccination campaign responses

Early reports of the events of concern seemed to indicate the presentation rate for the specific blood clots of concern might be higher for women of younger ages,[1] UK Medicines and Healthcare products Regulatory Agency (MHRA) found examples across all genders and ages,[37][better source needed] their data skewing towards these specific blood clots being more prevalent in AZD1222 vaccinated persons of younger ages.[44]

The WHO has continued to stress the administration of vaccines is based on risk versus benefit analysis.[45] Some variables that may be factored into such analysis include risk of an individual from catching COVID‑19, which relate to the infection rate in that area, and the benefits to that individual if vaccinated and exposed to COVID‑19 which varies with age, versus whatever the risks of vaccination are to that individual.[44]

Regional and national responses

The advisory panel for the government of Ontario, Canada has recommended against the use of heparin for management of thrombosis after vaccination until more is known.[54]

In response to the concerns over the adverse effects relating to rare blood clotting types Germany has suspended use of the AZD1222 in those under 60 years of age; in contrast to a period previously having suspended use of AZD1222 to over–65s due to limited data of the efficacy of the vaccine to this age group at that time.[55]

Following a few days of suspended use of AZD1222, the Ministry of Health, Welfare and Sport of the Netherlands decided to continue administering the vaccine only to persons above the age of 60.[56]

On 8 April 2021, the Australian Technical Advisory Group on Immunisation (ATAGI) advised the Australian Government that the Pfizer COVID‑19 vaccine is recommended over AZD1222 for adults aged under 50 years. The advice is "based on the increasing risk of severe outcomes from COVID‑19 in older adults (and hence a higher benefit from vaccination) and a potentially increased risk of thrombosis with thrombocytopenia following AstraZeneca vaccination in those under 50 years."[20] AZD1222 is still recommended by ATAGI for people over 50, and those under 50 who have already had their first dose with no ill effects.[20] In the state of Victoria, there were reports of some, aged under 50, being turned away from vaccination centres, despite having confirmed appointments. It is understood a special consent process will be developed by the Australian Government for people under 50 who choose to receive the AZD1222 vaccine.[57]

Studies

A study convened by a group of British hematologists on 19 March 2021, just two days after the acknowledgement of the condition, published its finding in The New England Journal of Medicine, establishing case definition criteria. The study included 294 participants who presented with symptoms of thrombocytopenia and thrombosis after receipt of the first dose of the Oxford–AstraZeneca COVID‑19 vaccine, showing an independent association between baseline platelet count and the presence of intracranial hemorrhage. The study established that 85% of the participants effected by the condition were aged younger than 60 years, and that those participants with a history of thrombosis or prothrombotic disorders did not appear to be at increased risk. The study showed an overall mortality rate of 22% and set out plans for additional research to determine the genetic factors that may increase risk of the condition and identify potential therapeutic agents.[58]

References

Notes

  1. ^ The Oxford–AstraZeneca COVID‑19 vaccine is codenamed AZD1222,[8] and later supplied under brand names, including Vaxzevria[9] and Covishield.[10][11]

Footnotes

  1. ^ a b c d e Greinacher A, Thiele T, Warkentin TE, Weisser K, Kyrle PA, Eichinger S (June 2021). "Thrombotic Thrombocytopenia after ChAdOx1 nCov-19 Vaccination". The New England Journal of Medicine. 384 (22): 2092–101. doi:10.1056/NEJMoa2104840. PMC 8095372. PMID 33835769.
  2. ^ a b Cines DB, Bussel JB (June 2021). "SARS-CoV-2 Vaccine-Induced Immune Thrombotic Thrombocytopenia". The New England Journal of Medicine. 384 (23): 2254–2256. doi:10.1056/NEJMe2106315. PMC 8063912. PMID 33861524.
  3. ^ Liu Y, Shao Z, Wang H (December 2021). "SARS-CoV-2 vaccine-induced immune thrombotic thrombocytopenia". Thrombosis Research. 209: 75–79. doi:10.1016/j.thromres.2021.12.002. PMC 8647389. PMID 34894531.
  4. ^ a b Klok FA, Pai M, Huisman MV, Makris M (November 2021). "Vaccine-induced immune thrombotic thrombocytopenia". The Lancet. Haematology. 9 (1): e73–e80. doi:10.1016/S2352-3026(21)00306-9. PMC 8585488. PMID 34774202. Although initially several terms were used to describe the syndrome … the term that has gained widespread use is vaccine-induced immune thrombotic thrombocytopenia (VITT). Thrombosis with thrombocytopenia syndrome has also been used, but it is a more general term that can be caused by other conditions
  5. ^ a b c d Warkentin TE, Pai M (October 2021). "Editorial on Thaler et al. long-term follow-up after successful treatment of vaccine-induced prothrombotic immune thrombocytopenia. Thromb Res 2021 in press". Thrombosis Research. 207: 158–160. doi:10.1016/j.thromres.2021.10.007. PMID 34757250. S2CID 239574011. We believe the name "VITT" works well … the term clearly denotes the key features of the disorder … provides a useful mnemonic for disease recognition in the usual sequence of events … need not mandate that thrombosis be present … "TTS" … has limited clinical utility, since many conditions … present with the duad of thrombosis and thrombocytopenia
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  33. ^ Nazy I, Sachs UJ, Arnold DM, McKenzie SE, Choi P, Althaus K, et al. (June 2021). "Recommendations for the clinical and laboratory diagnosis of VITT against COVID-19: Communication from the ISTH SSC Subcommittee on Platelet Immunology". Journal of Thrombosis and Haemostasis. 19 (6): 1585–1588. doi:10.1111/jth.15341. PMC 8250233. PMID 34018298.
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Further reading

  • Aleem A, Nadeem AJ (July 2021). "Coronavirus (COVID-19) Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT)". StatPearls. PMID 34033367.
  • Arepally GM, Ortel TL (July 2021). "Vaccine-induced immune thrombotic thrombocytopenia: what we know and do not know". Blood. 138 (4): 293–8. doi:10.1182/blood.2021012152. PMC 8172307. PMID 34323940.
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August 23, 2023
embolic, thrombotic, events, after, covid, vaccination, vitt, redirects, here, other, uses, vitt, disambiguation, post, vaccination, embolic, thrombotic, events, termed, vaccine, induced, immune, thrombotic, thrombocytopenia, vitt, vaccine, induced, prothrombo. VITT redirects here For other uses see VITT disambiguation Post vaccination embolic and thrombotic events termed vaccine induced immune thrombotic thrombocytopenia VITT 1 2 3 4 5 vaccine induced prothrombotic immune thrombocytopenia VIPIT 6 thrombosis with thrombocytopenia syndrome TTS 7 4 5 vaccine induced immune thrombocytopenia and thrombosis VITT 5 or vaccine associated thrombotic thrombocytopenia VATT 5 are rare types of blood clotting syndromes that were initially observed in a number of people who had previously received the Oxford AstraZeneca COVID 19 vaccine AZD1222 a during the COVID 19 pandemic 6 12 It was subsequently also described in the Janssen COVID 19 vaccine Johnson amp Johnson leading to suspension of its use until its safety had been reassessed 13 On 5 May 2022 the FDA posted a bulletin limiting the use of the Janssen Vaccine to very specific cases due to further reassesment of the risks of TTS although the FDA also stated in the same bulletin that the benefits of the vaccine outweigh the risks 14 In April 2021 AstraZeneca and the European Medicines Agency EMA updated their information for healthcare professionals about AZD1222 saying it is considered plausible that there is a causal relationship between the vaccination and the occurrence of thrombosis in combination with thrombocytopenia and that although such adverse reactions are very rare they exceeded what would be expected in the general population 12 15 16 17 Contents 1 Signs and symptoms 2 Causes 3 Diagnosis 4 Management 5 Epidemiology 5 1 Regulatory status 6 History 6 1 Organizations 6 2 Syndrome identification 6 3 Vaccination campaign responses 6 3 1 Regional and national responses 7 Studies 8 References 8 1 Notes 8 2 Footnotes 9 Further readingSigns and symptoms EditThe thrombosis events associated with the COVID 19 vaccine may occur 4 28 days after its administration and mainly affects women under 55 6 2 18 Several relatively unusual types of thrombosis were specifically reported to be occurring in those with the reaction cerebral venous sinus thrombosis and thrombosis of the splanchnic veins 19 20 Cerebral venous sinus thrombosis may cause severe headache stroke like symptoms weakness of a limb and or facial muscles seizures and coma 21 Splanchnic vein thrombosis may cause abdominal pain accumulation of fluid in the abdominal cavity and gastrointestinal bleeding 22 23 Other forms of thrombosis such as the more common pulmonary embolism may also occur Arterial thrombosis has also been reported 24 The low platelet count may manifest as petechia tiny blood spots under the skin beyond the site of the injection 19 Disseminated intravascular coagulation DIC diffuse formation of blood clots throughout the blood vessels of the body has been reported as part of the syndrome 25 DIC may cause a range of symptoms including abnormal bleeding breathlessness chest pain neurological symptoms low blood pressure or swelling 26 COVID 19 vaccines have some adverse effects that are listed as common in the two or three days following vaccination which are usually mild and temporary 19 Causes EditThe rare simultaneous occurrence of thrombocytopenia low blood platelets with blood clots after vaccination raised the original concern about this condition citation needed In many cases where acute thrombosis and thrombocytopenia have been found together after COVID 19 vaccination an antibody against platelet factor 4 has been identified 1 This phenomenon is mostly encountered in some people who have been administered heparin but none of the reported cases had received heparin 1 More rarely this phenomenon had previously been described as an autoimmune phenomenon in people who had not been exposed to heparin 27 One striking feature of thrombocytopenia in the presence of anti PF4 antibodies is the propensity of some to develop thrombosis a phenomenon called heparin induced thrombocytopenia if heparin is involved 28 Thrombocytopenia is generally a common symptom after or during many viral infections 29 and it has been consistently reported after intravenous administration of adenoviral gene transfer vectors 30 although its mechanisms are not yet clear There is no confirmed causal link to the syndrome and any COVID 19 vaccination citation needed however EMA is conducting investigations into AZD1222 and the Janssen COVID 19 vaccine Johnson amp Johnson for possible causal links 31 On 7 April 2021 the EMA noted one plausible explanation for the combination of blood clots and low blood platelets is an immune response leading to a condition similar to one seen sometimes in people treated with heparin that is heparin induced thrombocytopenia HIT 19 Diagnosis EditIn the United Kingdom professional societies led by the Royal College of Emergency Medicine have issued a guideline for suspected cases Someone presenting with concerning symptoms between five and 28 days after administration of the vaccine is assessed for a possible thrombotic complication with a full blood count which includes a platelet count as the initial investigation If the platelet count is decreased determination of the D dimer and fibrinogen levels may be performed with hematology expert advice recommended if these are elevated above specific cut offs 24 Management EditGuidelines from professional societies recommend treatment with alternative anticoagulants instead of heparin as there is a possibility that it may aggravate the phenomenon 32 33 Alternative options as the directly acting oral anticoagulants DOACs argatroban fondaparinux or danaparoid depending on the circumstances 32 Platelet transfusion is discouraged as this too may aggravate thrombosis 32 UK guidelines by the British Society for Haematology recommend the administration of intravenous immunoglobulin IVIG to reduce levels of the pathogenic antibody 32 Low fibrinogen levels may require correction with fibrinogen concentrate or cryoprecipitate 32 Epidemiology EditThis section needs to be updated The reason given is Needs to ensure latest data is reflected Marked as inacc as the information presented was not originally the basis of an Epidemiology section but discussion of age and possibly gender on the topic are relevant as vaccinations by countries may not have been spread evenly throughout ages and genders Please help update this article to reflect recent events or newly available information April 2021 The Paul Ehrlich Institute has recorded 31 cerebral venous sinus thromboses CVST and nine deaths out of 2 7 million vaccinated in Germany with the AZD1222 34 On 2 April 2021 the UK s Medicines and Healthcare products Regulatory Agency reported 22 cases of CVST and a further eight cases of clotting problems both associated with a low level of blood platelets following a rigorous review of its Yellow Card reporting The institute also reported finding no events of this type which occurred after vaccination with the Pfizer BioNTech COVID 19 vaccine 35 The EMA had earlier said that a link between certain very rare blood clots and the AstraZeneca vaccine is not proven but is possible 35 Observations in Germany of these rare events seemed to relate mostly women aged under 55 However because Germany had previously restricted AZD1222 to under 65s the population vaccinated there with AZD1222 is comparatively younger and consequently contained a higher proportion of women taking the contraceptive pill As CVSTs are more likely in women using hormonal contraceptives this inherent risk factor may be an influence on the reported preponderance of women experiencing these events following vaccination 34 1 The UK in contrast has applied its Pfizer and AZD1222 vaccines generally to older groups first then by decreasing age 34 The UK Medicines and Healthcare products Regulatory Agency MHRA reporting regards AZD1222 to 3 November 2021 recording 73 deaths out of 425 cases 17 in the context of 24 9 million first doses administered 36 37 Regulatory status Edit According to the European Medicines Agency EMA as of 28 March 2021 update the reported number of cases of embolic and thrombotic events after vaccination is lower than the rate of such events in the general population overall However the specific syndrome of embolic and thrombotic events in combination with low levels of blood platelets presenting in post vaccination cases raised the possibility of an association between the vaccine and the relatively rare syndrome The EMA also said that there is no proof that these events are caused by the vaccines but that the possibility could not yet be ruled out completely 12 Accordingly the EMA advised that people who received the vaccine and experienced symptoms suggestive of thrombosis including shortness of breath blurred vision and severe or persistent headache should seek medical attention 12 In a press briefing on 7 April 2021 38 39 Emer Cooke the executive director of the European Medicines Agency EMA began by stating Our safety committee the Pharmacovigilance Risk Assessment Committee PRAC of the European Medicines Agency has confirmed that the benefits of the AstraZeneca vaccine in preventing COVID 19 overall outweigh the risks of side effects COVID 19 is a very serious disease with high hospitalization and death rates and every day COVID is still causing thousands of deaths across the EU This vaccine has proven to be highly effective it prevents severe disease and hospitalization and it is saving lives Vaccination is extremely important in helping us in the fight against COVID 19 and we need to use the vaccines we have to protect us from the devastating effects 40 She went on to say The PRAC after a very in depth analysis has concluded that the reported cases of unusual blood clotting following vaccination with the AstraZeneca vaccine should be listed as possible side effects of the vaccine 41 At the same briefing Dr Samina Strauss of PRAC confirmed our conclusion is that these clotting disorders are very rare side effects of the vaccine 42 The UK Medicines and Healthcare products Regulatory Agency MHRA held a news conference on 7 April 2021 and while there is no proof that the AZD1222 vaccination caused the rare blood clots they indicated the possibility of a link is getting stronger 43 The UK is to offer under 30s alternative vaccines 43 The reasoning is because in the 20 29 age range the benefits to individual of vaccination were less as their likelihood of harm from COVID 19 is less and closer to the potential risk of harm from the vaccine at a medium exposure risk with COVID 19 infection cases running at a rate of 60 per 100 000 44 43 For higher age groups the benefit to risk ratio increased 43 Also on 7 April 2021 an interim statement from the WHO said its advisory body GACVS found any causal relationship between the rare blood clot cases and AZD1222 to be plausible but is not confirmed 45 On 20 April 2021 the safety committee of the EMA PRAC found a possible link to very rare cases of unusual blood clots with low blood platelets for the Johnson amp Johnson Janssen vaccine and required that these rare events similar to those noted for AZD1222 should be listed as a very rare side effect The EMA states the overall risk benefit for the Janssen vaccine remains positive 46 On 16 December 2021 the US Centers for Disease Control and Prevention CDC recommended the Moderna and Pfizer BioNTech vaccines should be preferred over the Janssen vaccine following growing concerns about rare blood clots 47 48 Janssen should still be offered to people who specifically request it 49 History EditOrganizations Edit Global vaccine safety comes under the remit of the World Health Organization WHO and in particular its Global Advisory Committee on Vaccine Safety GAVCS Other drug regulatory agencies significantly involved include citation needed European Medicines Agency EMA the regional regulatory authority for the EU Medicines and Healthcare products Regulatory Agency MHRA the medical authority for the United Kingdom Paul Ehrlich Institute PEI a German federal agency supervised by the Federal Ministry of Health with expertise in vaccines and biomedicines It is a WHO collaborating centre 50 Syndrome identification Edit A number of COVID 19 vaccines began to become approved and available at scale in December 2020 with vaccinations beginning to ramp up at scale from the beginning of 2021 among them the Oxford AstraZeneca COVID 19 vaccine based on an adenovirus vector and internally termed AZD1222 citation needed On 11 March 2021 the EMA issued a statement noting Denmark had suspended AZD1222 vaccinations due to a vaccinated patient dying with blood clots While noting there had been reports of other vaccinated people having blood clots and that its safety committee is already reviewing such cases the number of thromboembolic events in vaccinated people is no higher than in the general population 51 The World Health Organization WHO Global Advisory Committee on Vaccine Safety on 19 March 2021 issued a statement relating to safety signals related to AZD1222 relating to thromboembolic events and thrombocytopenia following review of available data and conclusions included that AZD1222 a positive benefit risk profile with tremendous potential to prevent infections and reduce deaths across the world 52 In its safety update of 29 March 2021 the EMA indicated it had initiated investigations into the very rare cases of specific embolic and thrombotic events in combination with thrombocytopenia low levels of blood platelets and related bleeding including disseminated intravascular coagulation and cerebral venous sinus thrombosis CVST noting any link with AZD1222 is not proven but could not be excluded 12 The EMA also initiated an assessment for all COVID 19 vaccines used in the EU for immune thrombocytopenia ITP described as low blood platelet levels that could lead to bruising and bleeding as a possible side effect whilst also stating that up to this point no link with any COVID 19 had been established 12 On 7 April 2021 the EMA determined that unusual blood clots with low blood platelets should be listed as very rare side effects of AZD1222 with WHO and UK EHRA issuing generally similar statements on the same day None of the agencies found a confirmed causal link between the vaccine and these incidents at the time but were listing them out of an abundance of caution 19 43 45 A highlight of minutes of the EMA s Pharmacovigilance Risk Assessment Committee PRAC concluding 9 April 2021 indicating they also were investigating four cases of unusual blood clots with low blood platelets including one death amongst people who had taken the Janssen COVID 19 vaccine The Janssen vaccine is approved but not yet deployed in the EU though vaccinations are in progress in the US PRAC has determined that it is not clear if there is a causal association Should regulatory action prove necessary PRAC have indicated the likely outcome would be an update to product information characteristics 53 Vaccination campaign responses Edit Early reports of the events of concern seemed to indicate the presentation rate for the specific blood clots of concern might be higher for women of younger ages 1 UK Medicines and Healthcare products Regulatory Agency MHRA found examples across all genders and ages 37 better source needed their data skewing towards these specific blood clots being more prevalent in AZD1222 vaccinated persons of younger ages 44 The WHO has continued to stress the administration of vaccines is based on risk versus benefit analysis 45 Some variables that may be factored into such analysis include risk of an individual from catching COVID 19 which relate to the infection rate in that area and the benefits to that individual if vaccinated and exposed to COVID 19 which varies with age versus whatever the risks of vaccination are to that individual 44 Regional and national responses Edit This section needs expansion You can help by adding to it April 2021 The advisory panel for the government of Ontario Canada has recommended against the use of heparin for management of thrombosis after vaccination until more is known 54 In response to the concerns over the adverse effects relating to rare blood clotting types Germany has suspended use of the AZD1222 in those under 60 years of age in contrast to a period previously having suspended use of AZD1222 to over 65s due to limited data of the efficacy of the vaccine to this age group at that time 55 Following a few days of suspended use of AZD1222 the Ministry of Health Welfare and Sport of the Netherlands decided to continue administering the vaccine only to persons above the age of 60 56 On 8 April 2021 the Australian Technical Advisory Group on Immunisation ATAGI advised the Australian Government that the Pfizer COVID 19 vaccine is recommended over AZD1222 for adults aged under 50 years The advice is based on the increasing risk of severe outcomes from COVID 19 in older adults and hence a higher benefit from vaccination and a potentially increased risk of thrombosis with thrombocytopenia following AstraZeneca vaccination in those under 50 years 20 AZD1222 is still recommended by ATAGI for people over 50 and those under 50 who have already had their first dose with no ill effects 20 In the state of Victoria there were reports of some aged under 50 being turned away from vaccination centres despite having confirmed appointments It is understood a special consent process will be developed by the Australian Government for people under 50 who choose to receive the AZD1222 vaccine 57 Studies EditA study convened by a group of British hematologists on 19 March 2021 just two days after the acknowledgement of the condition published its finding in The New England Journal of Medicine establishing case definition criteria The study included 294 participants who presented with symptoms of thrombocytopenia and thrombosis after receipt of the first dose of the Oxford AstraZeneca COVID 19 vaccine showing an independent association between baseline platelet count and the presence of intracranial hemorrhage The study established that 85 of the participants effected by the condition were aged younger than 60 years and that those participants with a history of thrombosis or prothrombotic disorders did not appear to be at increased risk The study showed an overall mortality rate of 22 and set out plans for additional research to determine the genetic factors that may increase risk of the condition and identify potential therapeutic agents 58 References EditNotes Edit The Oxford AstraZeneca COVID 19 vaccine is codenamed AZD1222 8 and later supplied under brand names including Vaxzevria 9 and Covishield 10 11 Footnotes Edit a b c d e Greinacher A Thiele T Warkentin TE Weisser K Kyrle PA Eichinger S June 2021 Thrombotic Thrombocytopenia after ChAdOx1 nCov 19 Vaccination The New England Journal of Medicine 384 22 2092 101 doi 10 1056 NEJMoa2104840 PMC 8095372 PMID 33835769 a b Cines DB Bussel JB June 2021 SARS CoV 2 Vaccine Induced Immune Thrombotic Thrombocytopenia The New England Journal of Medicine 384 23 2254 2256 doi 10 1056 NEJMe2106315 PMC 8063912 PMID 33861524 Liu Y Shao Z Wang H December 2021 SARS CoV 2 vaccine induced immune thrombotic thrombocytopenia Thrombosis Research 209 75 79 doi 10 1016 j thromres 2021 12 002 PMC 8647389 PMID 34894531 a b Klok FA Pai M Huisman MV Makris M November 2021 Vaccine induced immune thrombotic thrombocytopenia The Lancet Haematology 9 1 e73 e80 doi 10 1016 S2352 3026 21 00306 9 PMC 8585488 PMID 34774202 Although initially several terms were used to describe the syndrome the term that has gained widespread use is vaccine induced immune thrombotic thrombocytopenia VITT Thrombosis with thrombocytopenia syndrome has also been used but it is a more general term that can be caused by other conditions a b c d Warkentin TE Pai M October 2021 Editorial on Thaler et al long term follow up after successful treatment of vaccine induced prothrombotic immune thrombocytopenia Thromb Res 2021 in press Thrombosis Research 207 158 160 doi 10 1016 j thromres 2021 10 007 PMID 34757250 S2CID 239574011 We believe the name VITT works well the term clearly denotes the key features of the disorder provides a useful mnemonic for disease recognition in the usual sequence of events need not mandate that thrombosis be present TTS has limited clinical utility since many conditions present with the duad of thrombosis and thrombocytopenia a b c Use of AstraZeneca COVID 19 vaccine in younger adults Press release Health Canada 29 March 2021 Archived from the original on 11 October 2021 Retrieved 2 April 2021 Long B Bridwell R Gottlieb M November 2021 Thrombosis with thrombocytopenia syndrome associated with COVID 19 vaccines The American Journal of Emergency Medicine 49 58 61 doi 10 1016 j ajem 2021 05 054 PMC 8143907 PMID 34062319 AstraZeneca COVID 19 Vaccine AZD1222 PDF ACIP COVID 19 Emergency 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Pai M Grill A Ivers N Maltsev A Miller KJ Razak F et al 2021 Vaccine Induced Prothrombotic Immune Thrombocytopenia VIPIT Following AstraZeneca COVID 19 Vaccination Ontario COVID 19 Science Advisory Table doi 10 47326 ocsat 2021 02 17 1 0 Archived from the original on 2 April 2021 Retrieved 3 April 2021 Covid How does the Oxford AstraZeneca vaccine work BBC 6 April 2021 Archived from the original on 7 April 2021 Retrieved 6 April 2021 Ministerie van Volksgezondheid Welzijn en Sport 8 April 2021 Prikken met AstraZeneca voor mensen van 60 jaar en ouder gaat door Rijksoverheid in Dutch Archived from the original on 8 April 2021 Retrieved 8 April 2021 ABC News 9 April 2021 People under 50 turned away from Melbourne vaccination centre after new AstraZeneca advice www abc net au Archived from the original on 9 April 2021 Retrieved 9 April 2021 Pavord S Scully M Hunt BJ Lester W Bagot C Craven B et al October 2021 Clinical Features of Vaccine Induced Immune Thrombocytopenia and Thrombosis The New England Journal of Medicine 385 18 1680 89 doi 10 1056 NEJMoa2109908 PMID 34379914 Further reading EditAleem A Nadeem AJ July 2021 Coronavirus COVID 19 Vaccine Induced Immune Thrombotic Thrombocytopenia VITT StatPearls PMID 34033367 Arepally GM Ortel TL July 2021 Vaccine induced immune thrombotic thrombocytopenia what we know and do not know Blood 138 4 293 8 doi 10 1182 blood 2021012152 PMC 8172307 PMID 34323940 Iba T Levy JH Warkentin TE January 2022 Recognizing Vaccine Induced Immune Thrombotic Thrombocytopenia Crit Care Med 50 1 e80 e86 doi 10 1097 CCM 0000000000005211 PMC 8670081 PMID 34259661 Schultz NH Sorvoll IH Michelsen AE Munthe LA Lund Johansen F Ahlen MT et al June 2021 Thrombosis and Thrombocytopenia after ChAdOx1 nCoV 19 Vaccination N Engl J Med 384 22 2124 30 doi 10 1056 NEJMoa2104882 PMC 8112568 PMID 33835768 Scully M Singh D Lown R Poles A Solomon T Levi M et al June 2021 Pathologic Antibodies to Platelet Factor 4 after ChAdOx1 nCoV 19 Vaccination N Engl J Med 384 23 2202 11 doi 10 1056 NEJMoa2105385 PMC 8112532 PMID 33861525 Portals Medicine Viruses COVID 19 Retrieved from https en wikipedia org w index php title Embolic and thrombotic events after COVID 19 vaccination amp oldid 1170147470, wikipedia, wiki, book, books, library,

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