Pfizer’s Vaccine Efficacy Estimates For Children Dismissed As Unreliable

The CDC panel is getting ready to decide on Saturday which children under the age of five can receive the immunizations. But in the middle of this, Pfizer’s vaccine efficacy estimates for children have been dismissed as unreliable.

Even as the vaccine is about to be given to millions of American newborns and toddlers, the efficacy statistics Pfizer has provided for its COVID-19 vaccination for young children are being condemned as untrustworthy.

According to a Pfizer clinical research, the efficacy was 80.3 percent generally, 82.3 percent for children aged 2 to 5, and 75.5 percent for children aged 6 months to 2 years.

The Food and Drug Administration (FDA) stated in a statement on June 17 that those estimations were “not to be reliable due to the low number of COVID-19 cases that occurred in study participants.”

Only 10 COVID-19 cases—seven in children who got a placebo and three in children who received the vaccine—were used to generate the estimates. All took place after February 7.

But in sessions this week with vaccine advisory panels for the FDA and Centers for Disease Control and Prevention (CDC), they were presented as proof the vaccination should be administered to children across the nation.

Dr. William Gruber, senior vice president for vaccine clinical research and development at Pfizer, informed panelists during a meeting on Friday that “high efficacy was observed in the course of this trial.”

Additionally, Gruber displayed a slide with the data.

Due to the small number of cases, the confidence intervals, which express how sure one can be in the data, are wide-ranging.

According to Dr. Harvey Risch, a professor of epidemiology at the Yale School of Public Health, the stated efficacy is “a meaningless statistic.”

During one of the discussions, a CDC representative recognized that the efficacy might eventually wind up being significantly different from the figures Pfizer is pushing.

“I would really hope in our communications that we not use that 80% effectiveness because my level of confidence in that number—I believe the vaccine is effective; I do not have any idea what that number will actually end up being,” Dr. Amanda Cohn, the official, said.

“Thirty days after vaccination, this could fall off very quickly, and we just want to monitor it closely,” she added.

When the panel heard from Gruber on Friday, Dr. Sarah Long, a member of the Advisory Committee on Immunization Practices, who assists the CDC on vaccination recommendations, was one of several who held a similar opinion.

Because there are so few cases, she added, “I just think we should assume we don’t have efficacy data.”

Long was responding after the FDA had approved the COVID-19 vaccinations from Pfizer and Moderna for infants and toddlers.

The vaccine producers’ major goals were specified levels of neutralizing antibodies, assumed to be a measure of protection against SARS-CoV-2, the virus that causes COVID-19.

A subgroup of trial participants was used by the businesses to contrast the levels of antibodies the vaccines induced with those observed in a randomized group of adults from studies completed in 2020.

At the time, the FDA’s commissioner, Dr. Stephen Hahn, stated in interviews that the organization would not approve any COVID-19 vaccinations unless they were at least 50% effective. The agency said that it “would expect that a COVID-19 vaccine would prevent disease or decrease its severity in at least 50% of people who are vaccinated.”

However, it eventually provided drug companies with vaccination authorizations with a workaround. They could now compare antibody levels in populations for which the vaccines were not yet approved to adult levels from earlier trials using a method called immunobridging.

Both Pfizer and Moderna profited.

In the end, Pfizer compared the impact of three doses on children to that of two doses on adults. Moderna continued to use a two-dose main protocol.

Clinical effectiveness, or defense against infection, was only measured incidentally by the firms.

“Remember, the efficacy was not a requirement for approval,” Gruber said.

If adopting the case definition from the trial, Moderna’s trial found efficacy to be below average; just 43.7 percent effective in the youngest group and 37.5 percent successful in the other children. The efficacy increased a little bit, but not much, when using the CDC’s clinical criteria.

Pfizer’s was estimated substantially higher, but officials now claim that it cannot be trusted.

Leading FDA official Dr. Peter Marks told reporters during a call on June 17 that Moderna’s evidence was “more mature” than Pfizer’s.

The Moderna trial had a median followup period of more than two months. Contrarily, for infants and toddlers, Pfizer participants had median followup times of just 35 and 40 days, correspondingly.

Because the second dose of Pfizer’s experiment offered essentially no protection against infection, a third dose was added, which is what caused the problem.

“I think we will have to wait a little bit longer for Pfizer to have more mature effectiveness data to have to have the kind of confidence that we’d like to put out numbers,” Marks added.

Officials, though, insist that the inaccurate projections are irrelevant.

“From FDA’s perspective, we would have been confident in the clinical benefit of this three-dose primary series based on the immunobridging alone, even if there were no efficacy data,” Dr. Dorian Fink, another FDA official, told the CDC advisory panel.

Risch is opposed.

“Immunobridging is irrelevant if there is approximately no serious risk to start with, which is the case for healthy children,” he said.

The CDC panel is getting ready to decide on Saturday which children under the age of five can receive the immunizations.

Long, one of the panelists, said she was prepared to support widespread use even in the absence of valid efficacy data.

“I would be comfortable enough with the immunobridging,” she said.

As soon as youngsters outside of clinical trials receive the vaccinations, according to officials and the vaccine manufacturers, additional effectiveness statistics will be available.

“Exactly what the vaccine efficacy is after dose three I think needs further data to inform,” Fink said. “And we would expect to get some of these data hopefully from updated analyses from the clinical trial if more cases are accrued recognizing of course that if the vaccine is authorized, that will result in unblinding of placebo recipients so they can get their three-dose series … and also from real-world effectiveness data.”