AMSTERDAM — It’s happened, thus far, in an almost absurdly small number of patients, which is why the European Medicines Agency, while acknowledging the possibility Johnson & Johnson’s COVID-19 vaccine might trigger blood clots, said Tuesday that benefits from using the injection outweigh the risks.
The agency will require, however, that Johnson & Johnson relabel the vaccine with a warning.
“And it says we want you to know about this (possible side effect),” said William Schaffner, MD, an infectious disease and immunization specialist at Vanderbilt University in Nashville, Tennessee. “So if you come to be vaccinated with this vaccine, you make a choice.”
Schaffner, a consultant to the very panel that advises the FDA on vaccines, said when considering the choice it’s important to keep things in perspective.
“At present, this is a needle in a haystack,” he said. “It occurs once in over every million doses that are administered. That’s rare.”
It’s incredibly rare. While the breast cancer drug tamoxifen has a 1.2 percent chance of causing blood clots to form -- just a bit above the long-term risk for blood clots from oral contraceptives -- the risk from the Johnson & Johnson vaccine, so far, is about .0001 percent, taking into account U.S. data showing six blood clot cases and close to seven million doses administered.
Not only is the incidence of blood clots rare with the vaccine -- but the clots are of a rare type. First, they generally appear in the brain and the abdomen. Second, they are accompanied by what would seem illogical hematology: low platelet counts or thrombocytopenia.
Illogical because platelets are involved in blood clotting.
Something else distinctive about the clots, so far, is that they seem to arise most often in a certain demographic.
“The early data would indicate that six of the cases occurred in women under the age of 50,” Schaffner said. “There was one case that occurred in a young man.”
If the advisory panel determines the incidence of clots is primarily confined to a specific at-risk group, it would have comfortable grounds to unpause the J&J vaccine but restrict its use to exclude those vulnerable.
“And so what we have to do is balance the risks,” Schaffner said. “The risks associated with the vaccine... Oh, but the risks associated with Covid if you don’t get vaccinated. So it’s not an easy decision.”
Still, Schaffer does expect the panel will make a decision Friday -- and if they do decide to unpause the vaccine, with or without use restrictions, Schaffer said it’s important to remember this simple truth about drug therapy.
“There’s no drug available and no vaccine available in the world that doesn’t have the occasional serious side effect,” he said. “The question is not whether we use them but how can we use them at the lowest possible risk, so we get the most benefit.”
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