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COVID-19 Resource Center

Source: ACIP.
Disclosures: Adalja, Shimabukuro and Talbot report no relevant financial disclosures.
April 14, 2021
2 min read
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CDC advisory group says it needs more info on J&J vaccine

Source: ACIP.
Disclosures: Adalja, Shimabukuro and Talbot report no relevant financial disclosures.
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A CDC advisory committee said Wednesday that it needs more information before it can decide whether to alter its recommendation for Johnson & Johnson’s COVID-19 vaccine.

The Advisory Committee on Immunization Practices (ACIP) convened 1 day after U.S. health officials recommended that the rollout of the Johnson & Johnson vaccine be paused while experts review six reported cases of a rare clotting event in people who received the vaccine.

Johnson and Johnson COVID vaccine
A CDC advisory committee said it needs more information on a series of rare blood clots before it can vote on whether to change its recommendation for the Johnson & Johnson COVID-19 vaccine.
Source: Adobe Stock.

The six cases of cerebral venous sinus thrombosis (CVST) with thrombocytopenia, or low levels of blood platelets, occurred out of the first 6.8 million doses of the one-shot vaccine administered in the U.S. as of April 12, the CDC and FDA said. As of Tuesday, one of the people had died and another was in critical condition.

All six cases occurred in women aged between 18 and 48 years who experienced symptoms 6 to 13 days after they received the vaccine, which is authorized for people aged 18 years or older in the U.S. No specific risk factors for these events have been identified, and the true background incidence of CVST with thrombocytopenia remains unknown, an ACIP work group said during Wednesday’s meeting.

Amesh A. Adalja

The ACIP considered several options, including recommending that vaccinations with the Johnson & Johnson shot resume fully in all adults or that they resume only in some populations, such as adults aged 50 years or older, or only men. It also considered formally recommending that the pause be extended in order to gather more information, but ultimately decided not to hold a vote of any kind, leaving the pause in place.

Several concerns about formally voting to extend the pause were addressed, including that it could potentially dissuade people from getting the vaccine, interrupt ongoing trials or hinder the availability of the vaccine in countries with a more limited supply.

Instead, the ACIP decided to reconvene to discuss the matter further within a week or so. It also has an already scheduled meeting on May 5.

ACIP member Helen Keipp Talbot, MD, an associate professor of medicine at Vanderbilt University Medical Center, said the U.S. is in a “fortunate position” to be able to wait for more information on the vaccine.

“We have very good, well-proven alternatives that we are not seeing safety signals in,” Talbot said. “We can be much more cautious and thoughtful and follow the old motto of ‘Do no harm.’”

During the hours-long meeting, the ACIP reviewed the six U.S. cases and more than 100 similar events in Europe and the United Kingdom among people who received a different vaccine made by AstraZeneca. It heard from Johnson & Johnson representatives about the documented events, as well as two cases of CVST that occurred in a phase 3 clinical trial last year — one in a male participant aged 25 years who received the vaccine, and one in a 24-year-old female who was in the placebo arm of the study.

The Johnson & Johnson and AstraZeneca vaccines both use a modified adenovirus — a human vector in the Johnson & Johnson vaccine and a chimpanzee vector in the AstraZeneca vaccine — and experts have said the similar pattern of clotting may indicate that it is an issue related to the type of vaccine.

“However, it remains the case that the risk-benefit ratio strongly favors [these vaccines] and I worry that these decisions are going to cause a litany of cancellations for the Johnson & Johnson vaccine and a relegating of it to the second tier,” Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, told Healio on Tuesday after the pause was announced.

In a presentation Wednesday, the CDC’s Tom Shimabukuro, MD, MPH, said a “relatively crude analysis” showed that the observed rate of CVST following vaccination with the Johnson & Johnson vaccine “appeared to exceed” by at least three-fold what would be expected based on background rates among women aged 20 to 50 years.

In another presentation, Johnson & Johnson reported data from U.S. claims and electronic health records databases showing that the background incidence rate of CVST in females aged 18 to 34 is 2.64 per 100,000 person years, higher than in any other group.

The U.S. cases were reported through the Vaccine Adverse Event Reporting System. In Europe, regulators have recommended that “unusual blood clots with low blood platelets” be listed as a “very rare side effect” of the AstraZeneca vaccine, which has not been authorized for use in the U.S.

Beth Bell, MD, who chairs the ACIP’s COVID-19 vaccines work group, noted Wednesday that more than 160 clotting events have occurred after vaccination with the AstraZeneca vaccine in Europe and the U.K.

The Johnson & Johnson vaccine is also authorized in Europe, although doses have not been delivered yet and the drug maker said Tuesday that the rollout there has been delayed.

There have not been any reported cases of CVST among people who have received either of the other two vaccines authorized for use in the U.S. — the messenger RNA vaccines manufactured by Pfizer-BioNTech and Moderna. According to tracking by the CDC, more than 180 million doses of those vaccines have been administered in the U.S.