CDC and FDA Call for Pause on Johnson & Johnson Vaccine After Blood Clotting Cases

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The Baltimore plant’s certification by the F.D.A. has now been delayed while inspectors investigate quality control issues, sharply reducing the supply of Johnson & Johnson vaccine. The sudden drop in available doses led to widespread complaints from governors and state health officials who had been expecting much bigger shipments of Johnson & Johnson’s vaccine this week than they got.

States have been using the vaccine in a broad range of settings, including at mass vaccination sites and on college campuses. The vaccine’s one-shot approach has proved popular, and officials have directed it to transient, rural and isolated communities where following up with a second dose is more complicated.

It is common for regulators to investigate “safety signals” in new vaccines and other medical products. Very often, the signals prove not to be of concern. But the concerns about Johnson & Johnson’s vaccine mirror concerns about AstraZeneca’s, which European regulators began investigating last month after some recipients developed blood clots.

Out of 34 million people who received the vaccine in Britain, the European Union and three other countries, 222 experienced blood clots that were linked with a low level of platelets. The majority of these cases occurred within the first 14 days following vaccination, mostly in women under 60 years of age.

On April 7, the European Medicines Agency, the main regulatory agency, concluded that the disorder was a very rare side effect of the vaccine. Researchers in Germany and Norway published studies on April 9 suggesting that in very rare cases, the AstraZeneca vaccine caused people to make antibodies that activated their own platelets.

Nevertheless, the regulators argued, the benefit of the vaccine — keeping people from being infected with the coronavirus or keeping those few who get Covid-19 out of the hospital — vastly outweighed that small risk. Countries in Europe and elsewhere continued to give the vaccine to older people, who face a high risk of severe disease and death from Covid-19, while restricting it in younger people.

Both AstraZeneca and Johnson & Johnson use the same platform for their vaccine, a virus known as an adenovirus. On Tuesday, the Australian government announced it would not purchase Johnson & Johnson vaccines. They cited Johnson & Johnson’s use of an adenovirus. But there is no obvious reason adenovirus-based vaccines in particular would cause rare blood clots associated with low platelet levels.

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