U.S. regulators plan to decide by early July on whether to change the design of COVID-19 vaccines this fall in order to combat more recent variants of the coronavirus, with hopes of launching a booster campaign by October, a top Food and Drug Administration official said on Tuesday.

"The better the match of the vaccines to the circulating strain we believe may correspond to improve vaccine effectiveness, and potentially to a better durability of protection," Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, said at a meeting of outside advisers to the regulator.

The committee is scheduled to vote on a recommendation on whether to make the change later on Tuesday.

The updated shots are likely to be redesigned to fight the omicron variant of the coronavirus, experts say. The exact composition of the retooled shots and whether they also will include some of the original vaccine alongside new components will be considered at the meeting.

Pfizer Inc, Moderna Inc and Novavax Inc are scheduled to present data at the meeting. All three companies have been testing versions of their vaccines updated to combat the BA.1 omicron variant that was circulating and led to a massive surge in infections last winter.

Both Moderna and Pfizer with partner BioNTech have said that their respective redesigned vaccines generate a better immune response against BA.1 than their current shots that were designed for the original virus that emerged from China.

They have said that their new vaccines also appear to work against the more recently circulating BA.4 and BA.5 omicron subvariants, even though that protection is not as strong as against BA.1.

Experts also want to know if the new shots will boost protection against severe disease and death for younger, healthier people or merely offer a few months' additional safeguard against mild infection.

Scientists who have questioned the value of booster shots for young and healthy people have said a broad campaign is not needed with an updated shot either.

Other experts have championed any additional protection new vaccines may offer.