Of the 34 million people who received the vaccine in the UK, European Union and three other countries, 222 experienced blood clots that were associated with low platelet levels. Most of these cases occurred within the first 14 days after vaccination, mostly in women under 60 years of age.
On 7 April, the European Medicines Agency, the main regulatory agency, concluded This disorder was a very rare side effect of the vaccine. Researchers in Germany and Norway published the study on 9 April stating that in very rare cases, the AstraZeneca vaccine prompted people to make antibodies that activate their own platelets.
Still, regulators argued, the benefit of the vaccine – preventing people from getting infected with Kovid-19 or those who get it out of the hospital – is greatly affected by that small risk. The vaccine continued to be given to older people in Europe and other countries, prohibiting it in younger people with a higher risk of serious illness and death from Kovid-19.
Both AstraZeneca and Johnson & Johnson use the same platform for their vaccine, a virus known as adenovirus. On Tuesday, the Australian Government Announced It will not purchase Johnson & Johnson vaccines. He cited the fact that Johnson & Johnson, like AstraZeneca, used an adenovirus as the basis for their vaccines. But there is no clear reason that adenovirus-based vaccines will cause rare blood clots, especially associated with low platelet levels.
AstraZeneca has not yet applied for an Emergency Use Authority in the United States.
In addition to the Johnson & Johnson vaccines, the FDA has authorized vaccines developed by Modern and Pfizer-BioNotech. Those two vaccines use a different technique to produce immunity.
The first signs of concern about Johnson & Johnson’s vaccine came on April 9, when the European Medical Agency Announced They were investigating reports of four cases of blood clots in people receiving the Johnson & Johnson vaccine in the United States. A case in the clinical trial that occurred before the vaccine was authorized. Three vaccines occurred in the rollout. The agency said one of them was fatal.
Regulators described these reports as “safety signals” – a set of cases needed for further investigation. But he said it was unclear if the vaccines were due to clots.