Eleven blood clot cases linked to AstraZeneca in past week

The latest figures, contained in the Therapeutic Goods Administration’s (TGA) COVID-19 vaccine weekly safety report, bring Australia’s total number of thrombosis with thrombocytopenia syndrome (TTS) cases linked to the AstraZeneca vaccine to 104 (59 confirmed, 45 probable) from 7.4 million doses.
 
Ten of the cases recorded between 2–8 August were people aged 60 years or older, while five of the new probable TTS cases may be related to the second vaccine dose.
 
‘These cases remain under investigation and will be considered by an external panel of experts in the coming week to determine whether they are related to vaccination or not,’ the TGA report states.
 
‘All of the cases were in older people who presented with relatively mild symptoms, including common clots in the lungs or leg that are not uncommon with advancing age.
 
‘All patients have been discharged from hospital.’
 
The TGA’s latest report was released on the same day as a new UK study that found blood clots occurred in around one in 50,000 people aged under 50 who received the AstraZeneca vaccine during that country’s rollout.
 
Dr Sue Pavord, a consultant haematologist at Oxford University Hospitals NHS Foundation Trust and the lead author of the research, said the ‘very rare’ condition is particularly dangerous when the patient has a low platelet count and bleeding in the brain.
 
Half of the cases detailed in the analysis had no previous medical illness, and there appears to be no particular individual risk factors for the syndrome, Beverley Hunt, medical director of Thrombosis UK and professor of thrombosis and haemostasis at King’s College London, said.
 
Nearly one quarter (23%) of the cases contained in the UK study died, and the risk of death increased to 73% in patients with a very low platelet count and brain bleeds after blood clots in the brain.
 
In Australia, severe cases of TTS appear to be more common in women in younger age group. Nearly half of the TTS cases in women required treatment in intensive care, while serious Tier 1 cases were also twice as likely to occur in women compared to men.
 
However, Australia’s current TTS case fatality rate of 5.75% (six deaths from 104 probable or confirmed cases) appears to be much lower than that recorded in the UK study.
 
Aside from TTS, there were five reports of suspected immune thrombocytopenia (ITP) over the seven days covered by the TGA report, none of which were fatal.
 
Meanwhile, 38 additional cases of myocarditis and pericarditis associated with Pfizer were identified, bringing the total to 149 out of 6.3 million overall doses.
 
The most frequently reported side effects likely associated with both vaccines reportedly reflect what was seen in the clinical trials and include injection-site reactions such as a sore arm and more general symptoms like headache, muscle pain, fever and chills.
 
The TGA accepted an additional 2075 adverse events following immunisation (AEFI) in the week of 2–8 August, bringing the total to 48,143 from approximately 13.7 million vaccine doses administered in Australia. The observed number of deaths reported after vaccination so far remains less than the expected number of deaths that would occur naturally, or from other causes, for that proportion of the population.
 
The regulator also monitors uncommon side effects, and recently completed a detailed investigation of reports of swollen lymph nodes (lymphadenopathy) following immunisation.
 
Since the beginning of Australia’s vaccine rollout, the TGA has received more reports of enlarged lymph nodes after Pfizer than AstraZeneca – approximately 17 reports per 100,000 doses and six reports per 100,000 doses, respectively.
 
The majority of these reports were in younger people – most likely reflecting the higher use of Pfizer in these age groups – and occurred within a few days of vaccination before resolving themselves without treatment.
 
‘Common areas where enlarged lymph nodes might be noticed are in the neck, armpits and groin,’ the TGA report states.
 
‘Nothing unexpected was found [during the investigation] but we continue to monitor this side effect as part of our routine monitoring activities.’
 
The TGA report also stated that swollen lymph nodes could be linked to claims in the media that increasing breast size is a possible short-term effect of the Pfizer vaccine, as swollen lymph nodes under the arms which may give the impression of increased breast size.
 
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