CDC advisory panel unanimously approves expanded COVID vaccine boosters

CDC hearing came the day after the FDA expanded its authorization for booster shots.

On Thursday, the Centers for Disease Control's expert advisory committee on vaccines met to vote on new guidelines for the use of boosters to sustain the immunity provided by the COVID-19 vaccines in use in the US. The day prior, the Food and Drug Administration issued an emergency use authorization (EUA) that greatly expanded the number of vaccinated people who could receive a booster shot. That set the stage for the CDC to determine whether the FDA approval should be adopted as formal health policy.

A key step in the CDC's policymaking process is approval by its Advisory Committee on Immunization Practices (ACIP). While the CDC director isn't bound to follow ACIP's advice (and notably didn't in an earlier booster decision), overruling ACIP is unusual. Given that ACIP has now voted unanimously to expand booster use to Moderna and Johnson & Johnson vaccine recipients, the CDC director will likely follow its guidance.

FDA sets the stage

On Wednesday, the FDA announced that it was expanding its EUA for COVID-19 vaccine booster shots. Earlier this month, the FDA approved Pfizer/BioNTech boosters for people who are six months out from receiving their initial doses and are at risk of exposure (like health care workers) or severe COVID cases (the elderly and those with health conditions). The CDC approved this guidance despite a split vote against it from its advisory committee.

The FDA gives the same guidance to recipients of the Moderna vaccine as it gave for the Pfizer/BioNTech vaccine: It is approved for those over 65 years of age, those with medical conditions that place them at risk, and those with a job that increases their exposure to infections. For those who received the J&J shot, anyone over the age of 18 can get a second shot as soon as two months after their prior one.

The FDA also acted on evidence that mix-and-match boosters are highly effective. Accordingly, anyone who qualifies for a booster based on any of the rules described above is now authorized to receive any of these three vaccines.

The FDA's EUA, however, is simply a determinant of what's allowed. The CDC separately sets a policy for its preferred approach to vaccinations, based on the advice of ACIP—although as we saw earlier this month, the CDC director overruled some of ACIP's advice. The CDC's guidance is often taken into account by state and local health departments, insurance companies, and others, so it has a significant impact on how the FDA's authorizations are put into practice.

Data, so much data

Anyone who worries that we don't have the data to know enough about these vaccines—a group that sadly includes Florida's new surgeon general—should be forced to sit through the hours of presentations that the ACIP receives before voting. We now have multiple clinical trials (both industry- and government-funded) and several platforms for tracking adverse reactions among the vaccinated. And the numbers in some cases are staggering: Between clinical trials and ad-hoc boosting, the CDC has tracked nearly 11 million people who have already received vaccine booster doses.

While covering all the data is impossible, there were a number of recurring trends. One is that the rate of side effects from boosters is not significantly different from that of the initial vaccination. The most significant issues (heart inflammation from the RNA vaccines, clotting problems from the J&J) remain rare, and no new issues have been identified. Mostly, people get a bit feverish, achy, and/or tired.

Efficacy can be measured in myriad ways, from the level of neutralizing antibodies to the avoidance of severe symptoms, hospitalization, and death. All these factors do decline over time, though not necessarily in parallel—antibody levels tend to drop faster and more dramatically, for example, while protection from severe disease seems to fade more slowly. As one of the ACIP members noted during questioning, however, many of the people who got the vaccine early tend to be at high risk, which could exaggerate any apparent declines in avoiding severe disease.

In any case, even at points when antibody levels have dropped dramatically, the vaccines collectively provide significant protection (to cite one stat, unvaccinated people are 9–15 times more likely to end up in the hospital when infected). The J&J vaccine appears to provide less complete protection at early time points, but its efficacy seems to fade more slowly. By every measure we've tested so far, the boosters seem to reverse any declines that occur.

A somewhat-tentative OK

To an extent, the ACIP was charged not with determining whether boosters will help—they will—but whether using them provides a significant benefit over not doing so. The graph below, used during one of the presentations, makes clear that the answer is "it depends."

ACIP voted on two separate proposals: one for allowing Moderna boosters to be used among the same at-risk populations as the Pfizer/BioNTech boosters six months after the initial vaccination and one for allowing J&J recipients to get a booster at two months after.

The idea of a booster for J&J recipients generally got enthusiastic support from the ACIP members, apparently due to the vaccine's lower overall efficacy. There was more of a sense of grudging acceptance for the other proposal—we've committed to this policy for one RNA vaccine, and it's hard to justify a separate policy for the other. Most of the other comments involved ways in which the wording of the use guidance could be approved. (To give one example, a member suggested simply advising women to receive something other than the J&J vaccine for a booster, given that they are at the highest risk for its side effects.)

Despite some hesitance about some aspects of the decision, the final vote was unanimous, with all 15 members approving both proposals. The final decision now rests with CDC Director Rochelle Walensky.