Six adverse events out of 7 million people is ‘extremely rare’
On Tuesday, April 13, 2021, U.S. health agencies called for a “pause” in use of the Johnson & Johnson COVID-19 vaccine after ongoing safety monitoring identified a rare blood clotting disorder in six people who had received the vaccine.
Talking about vaccine safety is complex. Faced with uncertainty about the Johnson & Johnson vaccine, people are trying to understand and communicate these complex issues to the public. The Johns Hopkins International Vaccine Access Center offers these key messages for relaying accurate information to the public so individuals can make informed vaccination decisions.
Thus far, six people who received the Johnson & Johnson vaccine have experienced the rare blood clotting disorder, out of the nearly 7 million people who have received the vaccine to date. Therefore, the probability of experiencing this rare blood clotting side effect is less than one in a million. That means, among one million people vaccinated, one person may experience this adverse event. In other words, it is a million times more likely this adverse event will not occur after vaccination. A person is twice as likely to be struck by lightning in a year.
Nearly 7 million people have been vaccinated with the Johnson & Johnson vaccine in the U.S., most with only mild or no side effects. Out of an abundance of caution, use of that vaccine has been “paused” in the U.S.—that means, while the CDC and FDA are reviewing the six reported blood clotting disorder cases, it is recommended that the vaccine not be administered. This also helps health care providers be aware of the potential for this adverse event.
CDC’s expert advisory committee will convene this week to review the six cases and other data on the vaccine and provide recommendations. That means determining if these adverse events are actually related to the vaccine or not. The FDA will review the evidence and provide recommendations on how to proceed, including developing updated policies and guidance if needed.
We do not yet know if the blood clotting disorder experienced by these six individuals is related to the vaccine. We do know that the benefit of the vaccine — keeping people from being infected with the coronavirus or keeping those few who get COVID-19 out of the hospital — vastly outweighs the small risk of experiencing the blood clotting disorder. To date, nearly seven million people in the United States have received Johnson & Johnson shots—the vast majority have had no or mild side effects.
It is common for regulators to investigate “safety signals” in medical products, including new vaccines. Very often, the signals prove not to be of concern. A vaccine safety signal is information that indicates that there could be a potential link between a vaccine and an event previously unknown or incompletely documented. The signal will suggest a new potentially causal association (or a new aspect of a known association) between a vaccine and an event, which could be either adverse or beneficial. It’s important to be responsive to any safety concern. In the U.S., the FDA and CDC have many systems in place to find, report, and investigate any adverse events—even those that could turn out to be unrelated to the vaccines.
If people who received the Johnson & Johnson vaccine one to three weeks ago is experiencing severe headaches, abdominal pain, difficulty breathing, or swollen legs, they should contact a medical provider. Adverse events should also be reported to the CDC’s VAERS system.
Health care providers, public health practitioners, and communicators must continue to develop clear, evidence-based, practical, and easy-to-implement approaches to mitigate vaccine hesitancy and build trust in immunization.