The Centers for Disease Control and Prevention and the Food and Drug Administration lifted the pause on the Johnson & Johnson COVID-19 vaccine on April 23, 2021, but the labels and fact sheets given to patients will carry a warning about the exceedingly low risk of developing blood clots. Also, close monitoring of the J&J vaccine along with the Moderna and Pfizer vaccines that were given emergency use authorization will continue. Dr. William Petri, an infectious-disease physician and immunologist at the University of Virginia School of Medicine, explains this development and why the agencies decided that the benefits of the vaccine far outweigh the risks.
What was the concern with the Johnson & Johnson COVID-19 vaccine?
The FDA and CDC paused the use of the J&J vaccine on April 13, 2021 because of six initial cases of a rare and dangerous blood clot involving the cerebral venous sinuses, large blood vessels in the brain. This clotting, also called thrombosis, can also occur in the large blood vessels of the abdomen and legs and is associated with low platelet counts, or thrombocytopenia. This condition is called thrombosis with thrombocytopenia syndrome (TTS).
An unusual aspect of these clots is that they occur with a low platelet count. Platelets are cells in the blood that typically aid in clotting. TTS is likely caused by the J&J vaccination rarely causing the production of an antibody against part of a platelet called Heparin-Platelet factor 4. These antibodies induce the platelets to cause clots. TTS appears similar to a rare side effect from the blood thinner heparin called heparin-induced thrombocytopenia.
A panel of independent doctors and scientists known as the Advisory Committee on Immunization Practices (ACIP) extensively reviewed data after the pause. Upon further review of the total of 7 million doses of J&J vaccine administered, nine additional instances of this type of blood clot were identified, all in women.
Why did the CDC and FDA restart the use of the Johnson & Johnson COVID-19 vaccine?
First, the side effect is rare. According to the agencies, it has occurred at most in one in 100,000 young women receiving the Johnson & Johnson vaccine. No men nor women over 50 are thought to have had this side effect. Second, the J&J vaccine is highly effective at preventing COVID-19, which is a common and severe infection that has killed 1 in 500 Americans.
Third, the J&J vaccine has advantages over the mRNA vaccines made by Pfizer and Moderna in that it requires only a single dose. It also is easier to transport and store, since it does not require super-low temperatures as do the Pfizer and Moderna vaccines.
Fourth and most importantly, now that the side effect is known, people can make informed choices about which COVID-19 vaccine to receive. A young woman on oral contraceptives, which also can promote blood clots, might logically choose one of the mRNA vaccines, whereas a man might choose the J&J vaccine since it is a single dose. Young women are the riskiest group.
Is this side effect seen with the other COVID-19 vaccines?
The clots from TTS are treated with what are called directly acting anticoagulants, and not with heparin. This was part of the reason for the pause, so that word could get out to health care providers on how to properly treat this rare form of blood clots.
Should I get the J&J vaccine?
My recommendation if you are a woman under the age of 50 that you be immunized with the Pfizer or Moderna vaccines, and not the J&J vaccine. This is because this rare side effect has been observed only in young women; 13 of the 15 women who developed TTS are in this age group. For everyone else, the J&J vaccine offers the convenience of needing one and not the two doses of the other vaccines.
ABOUT THE AUTHOR
William Petri Jr., M.D., Ph.D., studies immunology and molecular pathogenesis of enteric infections and their consequences. The scope of research includes molecular parasitology of Entamoeba, innate immune host defense against Clostridium difficile, and in Bangladesh acquired immunity to Cryptosporidium. We study infections in mouse models, in humans (including clinical trials) and at the lab bench. Petri leads the PROVIDE study of the Bill & Melinda Gates Foundation that is exploring in Bangladesh and India the pathogenesis of enteric environmental dysfunction (EED) and its association with oral poliovirus and rotavirus vaccine failures, malnutrition and neurocognitive developmental delay. Petri has received from Governor Terry McAuliffe both the Commonwealth of Virginia Outstanding Faculty Award (2014) and the Outstanding Scientist Award (2017). He has been recognized at UVa with the Kadner Award for Graduate Teaching, the All-University Teaching, and Inventor of the Year Awards. Petri has served as President of the American Society of Tropical Medicine and Hygiene and Editor of Infection and Immunity, and is currently Associate Editor for PLoS Pathogens, Clinical Infections Diseases and Trends in Molecular Medicine. He has received the Oswald Avery Award of the Infectious Diseases Society of America, the Burroughs Wellcome New Investigator and Scholar Awards in Molecular Parasitology, and the Lucille P. Markey Scholar Award in Biomedical Research. He has served continuously since 1993 on advisory committees for the NIH. Bill Petri received the MD and PhD (Microbiology) degrees from UVA, did medicine residency at Case Western and returned to UVA for infectious diseases fellowship. He spends 3 months of every year caring for patients on the general medicine and infectious diseases services and the remainder is focused on research on infectious diseases, especially the molecular pathogenesis of diarrheal infections in children living in poverty in Bangladesh and the immunology of C. difficile infection in a mouse model and in patients at UVA hospital.