By Maryanne Demasi at Brownstone dot org.

Last week's meeting of the CDC's vaccine advisory panel was unlike any in recent memory.

It was the first full session of the new-look Advisory Committee on Immunization Practices (ACIP) - a panel now entirely handpicked by Health Secretary Robert F. Kennedy, Jr., and tasked with restoring public trust in vaccine policy.

Over two days, the committee tackled thorny topics such as Covid-19 vaccine safety, thimerosal in flu shots, and preparations for future infectious disease threats.

But it was a single vote - on whether to recommend a newly approved product called clesrovimab - that split the committee.

Clesrovimab, marketed as Enflonsia, is not a vaccine. It's a long-acting monoclonal antibody designed to prevent severe RSV illness in newborns during their first RSV season.

The CDC proposed offering it to all infants under eight months of age whose mothers hadn't received an RSV vaccine late in pregnancy.

Two members of the advisory panel - Dr Retsef Levi and Dr Vicky Pebsworth - voted 'no.'

Levi is no stranger to weighing risk. A professor at MIT with deep experience in data analytics and risk-based decision-making, he had combed through five clinical trials of RSV monoclonals, including clesrovimab and its predecessor, nirsevimab.

What he found gave him pause - in every trial, more infant deaths occurred in the treatment groups than in the control arms.

Levi acknowledged that the trials were small and not powered to detect 'statistical' differences in mortality - but the consistency of the imbalance was difficult to ignore.

Among the deaths were rare cases of gastroenteritis in otherwise healthy babies - events that defied easy explanation.

"Four different trials all show deaths going in the same direction," he told the meeting."Should we not be concerned that maybe there are some potential safety signals?"

What unsettled him further was that the CDC had not presented this data to the committee.

Shortly before the vote, Levi spoke not just as a scientist, but as a father. "I'm a scientist but I'm also a father of six children…If I had a premature baby, I might consider it. But giving this to a healthy newborn? I would be concerned to use that."

The rest of the committee voted in favour of recommending the product.

In the days following the meeting, co-chair of the committee Dr Robert Malone, elaborated on his reasoning in a public post.

He acknowledged the risks of RSV in infants are low - affecting about 2 to 3 percent - but said most severe cases occur in babies with no known risk factors. That makes it impossible to predict who will be hit hardest.

"This may seem like a small number - unless your baby is one of them," Malone wrote.

"The risks of the antibody product injections are much lower than the risk of your otherwise healthy baby being one of the unfortunate few that happens to develop severe RSV disease," he added.

To him, the broad recommendation was a pragmatic response to an unpredictable illness. With no way to know which infants might become critically ill, a single, long-acting dose before RSV season offered a measure of protection.

Levi, however, saw it differently.

He didn't feel the FDA, CDC, or Merck - the product's manufacturer - had adequately addressed the trial imbalances. The findings weren't statistically conclusive, but in Levi's view, they were too consistent to dismiss.

Instead, Levi advocated for a precautionary approach for an intervention aimed at healthy full-term newborns.

In this exclusive interview, Levi breaks down the data that shaped his dissenting vote, and reflects on the responsibility that comes with going against the majority.

Read the full interview with Dr Retsef Levi - edited for brevity.

DEMASI: Is it difficult to vote against your fellow panel members when the chair calls on you all to vote one by one?

LEVI: I don't think about it as voting against my fellow panel members. Each of us is there to make the best decision we can based ...