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What to watch for, report during J&J vaccine pause: CDC COVID-19 safety team

April 16, 2021

Editor’s note:For the latest news on COVID-19, visit

A COVID-19 vaccine safety leader credits astute health care providers and a robust vaccine safety surveillance system for the rapid identification of rare but serious cases of cerebral venous sinus thrombosis (CVST) and thrombocytopenia in six women who received the Johnson & Johnson (Janssen) COVID-19 vaccine.

Tom Shimabukuro, M.D., M.P.H., M.B.A., Centers for Disease Control and Prevention (CDC) COVID-19 Response Vaccine Safety team lead, explained at a webinar for clinicians how reporting to the Vaccine Adverse Event Reporting System (VAERS) is crucial, particularly when vaccinating large populations such as during the COVID-19 pandemic response.

“VAERS is designed specifically to rapidly detect rare, serious adverse events that might indicate a safety problem,” he said. “We were able to quickly detect this problem, assess it and now we're in the process of doing a more refined assessment to provide the necessary data to CDC and to FDA (Food and Drug Administration) and to the Advisory Committee on Immunization Practices (ACIP) to make evidence-based recommendations.”

The ACIP will hold a virtual emergency meeting from 11 a.m. to 5 p.m. EDT on April 23 to discuss the Johnson & Johnson (J&J) COVID-19 vaccine.

Dr. Shimabukuro said health care providers should monitor patients closely over the next two weeks and report symptoms if patients received the J&J vaccine. No cases of CVST with thrombocytopenia have been reported after receipt of either Pfizer or Moderna vaccines, he said.

“CVST with thrombocytopenia is a very rare condition nested in a rare condition,” Dr. Shimabukuro said. “It’s important that health care providers maintain a high index of suspicion when individuals show up and there is a history of Janssen COVID-19 vaccination.”

Symptoms often begin as headache, lethargy, gastrointestinal symptoms, chills and myalgia that are common among patients seeking care, he said. Later, the features become more focal and severe.

Symptoms in the six women occurred six to 13 days (median, eight days) after vaccination. Out of 7.2 million J&J vaccine doses administered to date, 3.7 million doses (52%) were administered between March 30 and April 13.

“Events post-vaccine may still occur after these doses, as they still remain within that risk window,” Sara Oliver, M.D., co-lead for the ACIP COVID-19 Vaccines Work Group, explained at the webinar.

Dr. Oliver said health experts do not yet have information on the following:

  • True background incidence of CVST with thrombocytopenia.
  • Specific risk factors for thrombocytopenic thrombotic events.
  • The incidence of other thrombotic events of non-CVST cases with thrombocytopenia after the vaccine.
  • True incidence of thrombocytopenic thrombotic events and CVST after the vaccine.

On April 14, the ACIP “agreed that more information is needed before a decision on vaccine policy could be made,” Dr. Oliver said. The ACIP’s next step is to review the “spectrum of policy options.”

The CDC and FDA will continue to identify and evaluate any cases within the risk window and past cases that may come to light because of the recent notifications, and formulate more precise data on observed vs. expected rates, including for specific demographic populations. They also will conduct a risk-benefit analysis and bring results to the ACIP, Dr. Oliver said.

Following are among the recommendations the ACIP could make after its April 23 meeting, Dr. Oliver said.

  • Determine the benefits of vaccination outweigh the risks overall, and recommend use of the vaccine in all adults 18 years and older.
  • Recommend use of the vaccine in some populations “with potentially age- or gender-specific recommendations, such as adults 50 years of age and older or males only, possibly,” Dr. Oliver said.
  • Decide that the risks outweigh the benefits and recommend against use of the vaccine in any population.

After the ACIP makes a recommendation on use of the J&J vaccine, it will be sent to the CDC director for approval.

To report an adverse event to VAERS, visit For help reporting, call 800-822-7967, email or view video instructions at

If contacted, health care providers should send records to VAERS as soon as possible. The Health Insurance Portability and Accountability Act permits reporting of protected information to public health authorities, including the CDC and FDA.

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