■ FDA review remains neutral on boosters ahead of critical Friday vote,

Experts to vote on recommendation for additional shots.

A highly anticipated Food and Drug Administration review of evidence on whether a booster shot of the Pfizer-biontech coronavirus vaccine is widely necessary struck a noncommittal tone Wednesday, setting the stage for a potentially fractious debate among expert advisers to the agency this week.

Pfizer and government officials have relied heavily on data from Israel in making the case to the public that boosters are necessary six months after full vaccination. But FDA reviewers cautioned that a raft of studies with clear limitations have emerged in the past few months, pointing out that “biases can affect their reliability.” The reviewers stated that “Us-based studies ... may most accurately represent vaccine effectiveness.”

Some studies have suggested the efficacy of the vaccines declines against symptomatic infections, but some have not, agency reviewers wrote.

“Overall, data indicate that currently Us-licensed or authorized COVID-19 vaccines still afford protection against severe COVID-19 disease and death in the United States,” they wrote. “There are many potentially relevant studies, but FDA has not independently reviewed or verified the underlying data or their conclusions.”

The documents were released in advance of the FDA’S full-day meeting with its vaccine advisory committee Friday. The outside experts will weigh whether the agency should approve a booster for the Pfizer-biontech shot. Pfizer was the first vaccine maker to file its application and data with the agency.

The experts will vote on whether a booster should be approved by FDA, but their recommendation is not binding. The agency typically follows the recommendations of its advisers.