WASHINGTON — The Centers for Disease Control and Prevention and the Food and Drug Administration on April 13 halted use of the one-dose Johnson & Johnson COVID-19 vaccine that has been given to 6.8 million people in the U.S.
The pause is due to reports of blood clotting in six people who have received the vaccine. One woman died, and another has been hospitalized in critical condition. Dr. William Petri, an infectious disease physician and immunologist at the University of Virginia School of Medicine, answers questions to help put this development in context.
What is this potential side effect of the J&J vaccine for COVID-19?
The potential side effect is a blood clot in the veins that drain blood from the brain. This is called central venous sinus thrombosis. In the vaccine-associated cases of this, platelets in blood, which are important for making clots, have been lower than normal. While researchers do not know for certain why this is so, platelet counts could be lower perhaps because they have been used up making these clots.
How many people have experienced this possible reaction?
About one in a million: Six cases out of the 6.8 million doses of the J&J vaccine administered in the U.S. These six cases all occurred in women ages 18-48, and from 6 to 13 days after vaccination. That’s about half as likely as getting struck by lightning in a year. What is being determined now is what is the normal background number of cases we might see in the general population without the vaccine as a factor. This will make it possible to determine if the clotting problem is a vaccine side effect or not.
What do I do if I got the J&J shot?
The CDC and FDA are recommending that people who have received the J&J vaccine within the last 3 weeks who develop severe headache, abdominal pain, leg pain or shortness of breath should contact their health care provider.
Fortunately this type of blood clot is treatable with the use of blood thinners or anticoagulants. If a patient has low platelets, however, a doctor would not prescribe the widely used anticoagulant heparin but instead another kind of blood thinner. Untreated, these blood clots can be fatal.