After federal health agencies in the U.S. recommended a temporary halt on using the Johnson & Johnson-Janssen COVID-19 vaccine, the Centers for Disease Control and Prevention (CDC) on April 14 convened a 13-member Advisory Committee on Immunization Practices (ACIP) to review the six reports of unusual blood clots occurring in people vaccinated with the shot. The ACIP sets policies for how any approved or, in the case of COVID-19, authorized, vaccines are to be used—when and how the shots should be given and to which age groups. After the meeting, the CDC said it would continue to recommend the pause.
The committee heard from representatives from J&J-Janssen, the U.S. Food and Drug Administration and the CDC’s immunization working group, which met on April 12 when the two federal agencies’ jointly-run Vaccine Adverse Event Reporting System (VAERS) picked up a potential trend of clotting associated with low platelet counts. All six cases the system identified were women, aged 18 to 48 years old, and involved cerebral venous sinus thrombosis (CVST)—clotting in the veins that drain blood from the brain—occurring alongside low platelet counts. That combination is unusual; normally clotting is not associated with low platelets, but in this condition, the body develops antibodies that lower platelet levels and as a result can block blood flow.
The CDC team monitoring the safety system were on the alert for clotting reports, given the recent spate of dozens of clotting cases linked to another vaccine, from AstraZeneca, that is not yet approved in the U.S. but used widely in Europe and the U.K. Both vaccines use a similar technology involving a weakened cold virus to deliver COVID-19 virus genes to the immune system.
The working group went through data on what is known about CVST in general, and assessed whether the rates seen with the cases linked to the J&J vaccine were on par with those. The problem, as the members noted during the meeting, was that most of the existing data on CVST do not also involve low platelet counts as well, which makes it difficult to assess whether the rates so far associated with the vaccine are of concern.
The working group also considered what policy options are available to respond to reports of this rare but serious side effect. Those included lifting the pause and limiting vaccination potentially to specific groups like older people for whom the blood-clotting risk appears to be lower and lifting the pause entirely and continuing with vaccination (which assumes the benefits of vaccination still outweigh the risks of clotting). During the four-hour meeting, representatives from Janssen presented detailed information about the cases of CVST reported both through the VAERS system as well as directly to the company itself, and argued for the latter course of action.
“To be very frank I do not want to vote on this issue today,” Dr. Beth Bell, professor of global health at the University of Washington and chair of the CDC working group said during the discussion period. “I don’t feel I have enough information to make an evidence-based decision.”
The group ultimately decided to extend the pause “for a limited time while awaiting additional information,” as Dr. Sara Oliver, a member of the team, said towards the end of the meeting. The decision reflected the unease that Bell and others expressed about making any type of recommendation at this point, since they were not satisfied with the data available for making a risk-benefit analysis.
The FDA, on the other hand, came up with a slightly different strategy after reviewing the cases of lifting the pause and continuing vaccination, suggesting at the committee meeting that individuals (with the help of experts) should decide whether or not the J&J shot is right for them. “Individuals, in consultation with their health care providers or vaccination providers, may arrive at a conclusion of favorable benefit-risk after taking into account demographic factors, risk exposure to SARS-CoV-2, and its severe outcomes, and access to other COVID-19 vaccines,” said Dr. Doran Fink, deputy director of the division of vaccines and related products applications at the FDA.
Some of the CDC’s ACIP members echoed the FDA’s focus and reminded their fellow committee participants of how much certain communities are relying on the single-shot J&J vaccine, which doesn’t require people to return for a second dose, as the two other vaccines authorized in the U.S., from Pfizer-BioNTech and Moderna do, and doesn’t require frozen storage as those vaccines do.
“Putting the vaccine on pause for those of us on the frontlines is devastating,” says Dr. Camille Kotton, an infectious disease expert at Massachusetts General Hospital. “We were planning on using this vaccine in the state of Massachusetts for people who are homebound and not otherwise able to get vaccinated. We were planning on using it for vulnerable inpatient populations who often have many [other chronic conditions] and are at high risk for COVID-19 but haven’t been able to get vaccinated otherwise. We were certainly going to use it in underserved populations that aren’t able to get the mRNA vaccines… Underserved populations do need access to this vaccine.”
Nevertheless, the ACIP appears to be taking a conservative approach, staying the course until it has more information. With 3.8 million people vaccinated in the past two weeks with the J&J shot, more cases of CVST and other types of clotting may come to light in coming weeks—including reports from people who were vaccinated earlier and developed clots but were unaware that their condition might be related to the vaccine. “In coming weeks we will have better information to assess the signal and possibly characterize the risk,” Dr. Tom Shimabukuro, deputy director of the immunization safety office at CDC said during the meeting.
That’s what the ACIP members are counting on, and the committee is planning to meet in a week or so to reassess any new reports of clotting to see if the additional data provide a better foundation for a recommendation to continue with the J&J vaccination for all adults, continue it with only a certain group of people, or decide to stop vaccinating with the shot altogether.
One important factor in the risk-benefit discussions is the fact that the J&J shot is not the only one available. “We are very fortunate because we have multiple other alternatives in the U.S. to help stop the pandemic that we have not seen safety signals in,” said Dr. Helen Talbot, associate professor of medicine at Vanderbilt University to the committee. “We can be much more cautious, and thoughtful and use the old model of first do no harm.”
While the pause may cause some people to question the safety of not just the J&J shot but those of other COVID-19 vaccines as well, experts agreed that if anything, the action should reassure the public that the vaccines they are getting are safe and effective, and that health officials are carefully monitoring for any potential problems associated with them. “This is an example of how robust the U.S. vaccine safety monitoring system is,” said Shimabukuro. “In this case of a mass scale vaccination program, the system worked, and VAERS functioned exactly as planned; it’s a success story for vaccine safety.”