The U.S. Pauses Johnson & Johnson Vaccine After Six Cases of Rare Blood-Clotting Disorder

May 5, 2021 | Jessica Wise | Outbreak News

Over seven million Americans have already received the single-dose Johnson & Johnson COVID-19 vaccine, with another ten million doses currently on their way to vaccination sites nationwide [1]. However, after six cases of a rare blood clotting disorder occurred in inoculated women, the US Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) decided to halt the use of this vaccine [1]. 

The six women who developed blood clots following inoculation experienced symptoms within one to two weeks after vaccination. The type of blood clot these women developed is called cerebral venous sinus thrombosis (CVST) and has also been seen in a few cases in Europe after receiving the AstraZeneca/Oxford COVID-19 vaccine [2]. A blood thinner called heparin is typically used to treat blood clots, but in some cases, the immune system reacts to heparin; this phenomenon is called heparin-induced thrombocytopenia and can increase a patient’s risk of clotting. Heparin cannot be used to treat these women, which makes treatment more complicated [2].

What does this mean? 

It is important to note that the risk of COVID-19 infection in the US is far greater than the risk of developing a blood clot. Americans who received the Johnson & Johnson vaccine several weeks ago should not be concerned about blood clots, as CVST occurred shortly after inoculation for these six women [3]. It is advised for those who experienced symptoms, such as severe headaches, shortness of breath, abdominal pain, or leg pain, within three weeks of inoculation to contact a physician. Other symptoms such as mild headaches and flu-like symptoms are expected after receiving the vaccine as the immune system is producing a defense against COVID-19 [3].

What happens next?

A panel of experts from the FDA and CDC will compare the incidence rate of blood clots shortly after Johnson & Johnson inoculation to the incidence rate of blood clots in the general, unvaccinated population to determine whether the occurrence of blood clots in these women was a coincidence or linked to the vaccine [4]. If experts conclude the cases of CVST to be linked to the vaccine, they will compare the risk of blood clots after vaccination to the risk of COVID-19 infection [4]. Most likely, to remove the Johnson & Johnson vaccine, a highly effective, easily storable vaccine, from the market, many more blood clotting events must occur [4].

What are the potential outcomes?

One possible outcome is the cessation of Johnson & Johnson vaccine use, but experts believe this is unlikely as it would require many more cases of CVST; currently, the risk of COVID-19 infection is exponentially greater than the risk of CVST [4]. The US may not be greatly affected if use of the J&J vaccine is permanently halted, but poorer countries are relying on the availability of an adenovirus vaccine as it is manufactured more quickly and economically than mRNA vaccines and requires only refrigeration and not deep freezing [5]. The other possibility is that officials end the pause and J&J vaccine use continues, either with or without restrictions on who can and/or should receive it [4].

The government decided to pause Johnson & Johnson vaccine use “out of an abundance of caution,” but this decision may exacerbate people’s concerns about receiving any COVID-19 vaccine [6]. However, pauses in a vaccine or drug use are not uncommon, and it is likely the medical issue caused by the vaccine or drug will be deemed a coincidence after investigation. A pause provides doctors with time to determine the best treatment methods for the medical issue. [3]. Overall, the pause on the J&J vaccine use reflects the federal government prioritizing COVID-19 vaccine safety.



As of April 25th, 2021, the FDA and CDC recommend use of the Johnson & Johnson COVID-19 vaccine in the United States, after a temporary pause. The vaccine’s benefits outweigh its risks, but women under 50 years of age should be aware of the very rare risk of blood clotting [7].










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