The Johnson & Johnson, or Janssen, COVID-19 vaccine is a single-dose vaccine to prevent COVID-19. This Snapshot feature addresses potential side effects and the controversies surrounding the recent blood clotting incidents.
The Johnson & Johnson COVID-19 vaccine, also called Ad26.COV2.S, was developed by Janssen Pharmaceuticals of Johnson & Johnson.
It is a single-dose vaccine, which differentiates it from two-dose COVID-19 vaccines, such as the ones from Pfizer and Moderna.
In early 2021, the Food and Drug Administration (FDA)Trusted Source and, after a recommendation from the European Medicines Agency (EMA), the European Commission issued emergency and conditional authorization for the Johnson & Johnson vaccine for individuals aged 18 years and older. The vaccine has been approved for emergency use in 40 countries.
However, the FDA recommended a pause in the vaccine’s use, as a precautionary measure following a small number of rare blood clot incidents. At the same time, Johnson & Johnson delayed the distribution of the vaccine in Europe while the EMA conducted its own review.
On April 20, the company announced it would resume distribution of its vaccine in the European Union but with a safety warning, after the EMA concluded that the vaccine’s benefits continue to outweigh its risks.
After halting vaccination in the United States a few weeks ago, the FDA and the CDC recently recommendedTrusted Source that vaccinations resume. They noted, however, that women under the age of 50 should be aware of the risk of rare blood clots.
Moreover, both agencies want women to know that alternative COVID-19 vaccines are available, for which there are currently no reports of rare blood clots.
The World Health Organization (WHO)Trusted Source has stated that, while it continues to monitor the safety responses from regulatory agencies, the vaccine is safe and effective against the severe risks of COVID-19.
The vaccine is categorized as a viral vector vaccine.
This vaccine form utilizes a different, harmless virus to deliver the genetic instructions for making the SARS-CoV-2 virus’ surface spike protein, which triggers the body’s immune response to produce antibodies. The vaccine does not contain the SARS-CoV-2 virus and cannot cause COVID-19.
The Johnson & Johnson vaccine has a 66% efficacy rate. While this is lower than the efficacy rates of the Pfizer or Moderna vaccines, it should be noted that the clinical trials of the Johnson & Johnson vaccine took place in different contexts — globally in regions where variants were more prevalent, and in the U.S. during a period of significant increase in COVID-19 cases.
According to the FDA’s vaccine fact sheet Trusted Source, possible side effects include:
As with other COVID-19 vaccines, the Johnson & Johnson vaccine has a low but potential risk of causing an allergic reaction.
An ingredient that has raised particular concerns about allergic response is polysorbate 80, a chemical that is structurally related to polyethylene glycol (PEG)Trusted Source, found in Pfizer’s and Moderna’s mRNA vaccines, both of which have prompted similar worries.