On Tuesday morning, the Food and Drug Administration and the Centers for Disease Control and Prevention issued a release acknowledging that an extremely rare clotting disorder was associated with the use of the Johnson & Johnson COVID vaccine. The problem is actually less than a one-in-a-million issue; in data from the US, where 6.8 million doses of this vaccine have been used, there have only been six instances of the clotting problem detected.
Because the clots call for an unusual treatment, however, the organizations are calling for a pause in administering the shot. This will provide them with time to ensure the medical community is aware of the appropriate treatment.
This is not the first vaccine to create extremely rare clotting issues. They’ve also been seen following use of the AstraZeneca vaccine. The problem appears to be caused by the harmless virus (an adenovirus) that carries a single gene from SARS-CoV-2 in order to elicit an immune response.
The leading hypothesis to explain the phenomenon is that, in very rare cases, the adenovirus triggers an immune response to factors found on the surface of platelets, which are an essential part of the clotting process. This activates platelets, causing clots, and at the same time reduces the total platelet count.
These seemingly contradictory changes make treating the issue through the normal approach to excessive clotting dangerous. Typically, the appearance of clots would call for using a treatment that would reduce the probability of clots forming. But due to the low platelet counts in these individuals, those treatments can make it much less likely that clots form when they’re needed.
It’s this difference between apparent patient needs and appropriate treatment that has caused the CDC and FDA to call for a pause in the use of the J&J vaccine.
CDC will convene a meeting of the Advisory Committee on Immunization Practices on Wednesday to further review these cases and assess their potential significance. FDA will review that analysis as it also investigates these cases. Until that process is complete, we are recommending a pause in the use of this vaccine out of an abundance of caution. This is important, in part, to ensure that the health care provider community is aware of the potential for these adverse events and can plan for proper recognition and management due to the unique treatment required with this type of blood clot.
The CDC and FDA highlight severe headache, abdominal pain, leg pain, or shortness of breath as potential symptoms of the clotting problem.
So far, all six cases have occurred among women below the age of 50 and appeared between one and two weeks after vaccination. Because of the rarity of the clotting disorder compared to the very large risks posed by COVID-19, most countries that initially suspended the use of the AstraZeneca vaccine re-started it with added precautions. Germany, for example, is using it for patients over 60, since they are at lower risk of clots and much higher risk of severe COVID-19.
It’s likely that the US will also resume use of the J&J vaccine, which still has an excellent overall safety profile, typically has lower side effects than two-dose vaccines, and is extremely effective.
Unfortunately, the US also has a large population of people who are hesitant about receiving any vaccines. Given their persistent worries, these events will likely feed into their paranoia. And their apparent resistance to facts will make it much harder for them to evaluate the risk calculation of an extremely rare side effect in a vaccine against a virus that’s frequently deadly.