A study published in the British Medical Journal (BMJ) showed a 30 per cent higher risk in developing rare blood clots from the AstraZeneca Covid vaccine, compared to Pfizer’s mRNA vaccine.
Based on health data from five European countries and the US, the study showed a small increased risk of TTS (thrombosis with thrombocytopenia syndrome) after a first dose of the Oxford-AstraZeneca vaccine, and a trend towards an increased risk after the Janssen/Johnson & Johnson vaccine, compared with the Pfizer-BioNTech vaccine, said the journal.
When the data was pooled together, “analysis showed a 30 percent increased risk of thrombocytopenia after a first dose of Oxford-AstraZeneca compared with Pfizer-BioNTech – an absolute risk difference of 8.21 per 100,000 recipients”, said the study. Though the condition may be very rare, these observed risks needed to “be considered when planning further immunisation campaigns and future vaccine development”, the researchers pointed out
The BMJ study comes even as mRNA vaccines hit the headlines worldwide, over possible links to cardiac-events.
Different approaches
Countries across the world have adopted different approaches to rolling-out the AZ vaccine, with some countries restricting this Covid-19 vaccine in young people and others in the elderly. In India, the Serum Institute has an alliance on the AZ-Oxford University vaccine, to make and market it in low and middle income countries. Serum’s Covishield ( the AZ vaccine) was given to those over 18 years and it carried the bulk (174 crore doses) of the 200 crore-plus vaccines deployed in the country.
Responding to the BMJ study’s finding, an AstraZeneca spokesperson told businessline, that clinical trials and real-world data showed Vaxzevria (AZ-Oxford vaccine) had an acceptable safety profile and the World Health Organization and other international bodies, had stated the benefits of vaccination outweighed any potential risks.
“According to data from three large, real-world studies with over seven million vaccinated individuals from the UK and Spain rates of rare blood clotting events are lower than in those diagnosed with Covid,” said the spokesperson, adding that no specific risk factors or definitive cause for these extremely rare events have been identified so far.