After receiving emergency use authorization from the Food and Drug Administration (FDA), Johnson & Johnson-owned Janssen Pharmaceuticals became the third company to make its coronavirus vaccine available in the country.
The Johnson & Johnson (J&J) SARS-CoV-2 viral vector vaccine joined mRNA vaccines made by Pfizer-BioNTech and Moderna to help prevent more severe COVID-19 outcomes, including hospitalizations and death.
The J&J one-shot vaccine for adults was another major step toward vaccinating millions of people across the country. While it is a single dose, easy to store logistical advantages make it an attractive option, there is also concern over the recent pause in J&J vaccine administration due to a rare brain blood clot combined with low platelets—cerebral venous sinus thrombosis in combination with thrombocytopenia.
These adverse events were identified through the Vaccine Adverse Event Reporting System, which is jointly managed by the Centers for Disease Control and Prevention (CDC) and FDA.
Nearly 7 million doses of the J&J vaccine have been administered, but the FDA and CDC are reviewing data involving six reported cases in the U.S. of cerebral venous sinus thrombosis (CVST) in combination with thrombocytopenia in people receiving the vaccination. All were in women between 18 and 48, with symptoms developing six to 13 days after vaccination.
This announcement comes on the heels of a similar syndrome reported in Europe after the administration of AstraZeneca’s viral vector vaccine, recently described in the New England Journal of Medicine as a vaccine-induced immune thrombotic thrombocytopenia. Oxford’s AstraZeneca is not yet authorized for use in the United States.
Two physician experts took time to share what patients should know about the J&J vaccine: AMA Chief Health and Science Officer Mira Irons, MD, and Sandra Fryhofer, MD, an Atlanta general internist who serves as the AMA’s liaison to the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP). Dr. Fryhofer also is a member of ACIP’s COVID-19 Vaccine Work Group.
Vaccination paused out of caution
The “CDC and FDA acted quickly and issued a joint statement recommending the pause,” Dr. Fryhofer said during a recent “AMA COVID-19 Update” an episode about the J&J Janssen COVID-19 vaccine pause. The CDC also “released additional information through its Health Alert Network,” which “could lead to more cases being reported as a result of increased awareness.”
“The pause means hold off on administering the vaccine for now. It’s a recommendation. It’s not a mandate, but it’s being made out of an abundance of caution,” she said. “This health alert also gives specific recommendations to clinicians about treatment nuances.
“It warns that in these cases, heparin, a standard therapy for blood clots, could cause tremendous harm,” Dr. Fryhofer added, noting that the “CDC advises checking for platelet-activating antibodies by doing a platelet factor four (PL4) antibody test.”
The “CDC advises against heparin therapy if platelet factor four antibody test is positive,” she said. “If PL4 test is positive, use of non-heparin anticoagulants and high dose intravenous immune globulin should be considered. Hematology consultation is also advised.”
While the ACIP convened an emergency meeting on April 14 to review the J&J vaccine safety concerns, a vote on the next steps was not made because more information was needed to make an evidence-based decision.
“This means the pause is still on for now, but this will give the CDC more time for risk refinement—to identify specific risk factors like age, gender as well as the effect of other factors, including use of estrogen-containing products like birth control pills and hormone-replacement therapy,” Dr. Fryhofer explained. “The pause is not indefinite. The plan is for ACIP to reconvene after additional risk refinement is complete.”
Blood clots with low platelets are extremely rare
“Some might say this pause is an overreaction—six people afflicted out of more than 6.8 million doses administered, so about one in 1 million,” said Dr. Fryhofer. “However, cerebral venous sinus thrombosis is a very
“CDC says the background rate of CVST is somewhere between two and 15 per million, but that includes all CVST cases,” she added. But “CVST is not usually associated with low platelet counts, so the combination of the two conditions—both blood clots and low platelets—is the red flag.”
“And as FDA’s Peter Marks, MD explained it’s not just the cerebral venous sinus thrombosis, it’s not just the thrombocytopenia, it’s the combination of them occurring together that makes a pattern,” said Dr. Fryhofer. “This pause will allow more time to determine if these events are a needle in a haystack or the tip of an iceberg.”
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