By Michael Erman and Leroy Leo

(Reuters) -Advisers to the U.S. Food and Drug Administration on Tuesday recommended a change in the design of COVID-19 booster shots this fall in order to combat more recently circulating variants of the coronavirus.

The FDA's Vaccines and Related Biological Products Advisory Committee voted 19-2 that the next wave of COVID booster shots should include a component that targets the Omicron variant of the coronavirus.

The FDA plans to decide by early July on what the design of the boosters should be.

FDA scientists at the meeting suggested they preferred vaccines that will target the BA.4 and BA.5 Omicron subvariants that are currently dominant rather than the BA.1 Omicron variant that led to a massive surge in infections last winter.

Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, said the regulator would hope to launch a booster campaign with a retooled vaccine by October.

"The better the match of the vaccines to the circulating strain we believe may correspond to improved vaccine effectiveness, and potentially to a better durability of protection," Marks told the meeting of outside expert advisers to the agency.

Pfizer Inc (NYSE:PFE), Moderna (NASDAQ:MRNA) Inc and Novavax (NASDAQ:NVAX) Inc presented data at the meeting. All three companies have been testing versions of their vaccines updated to combat the BA.1 Omicron variant.

Moderna said it would be ready with a "couple of hundred million" of bivalent, or double targeted, vaccines designed to combat BA.1 by September. It would be late October or early November if it needs to design a vaccine targeting the newer subvariants, the company said.

Pfizer said that it and partner BioNTech already has a significant amount of BA.1 vaccine ready and is preparing to produce a large amount of vaccine targeting BA.4 and BA.5. It said either could be ready for an early October rollout.

Dr. Kanta Subbarao, representing a World Health Organization advisory committee that also considered the issue, said she preferred BA.1-based vaccines, suggesting they could generate a broader immune response because that variant is more distinct from the original virus than its successor subvariants.

"Our goal here is to achieve broader immunity against circulating and emerging variants," Subbarao said, noting that trying to match what variant might be circulating in the fall is difficult because of uncertainty about the trajectory of the evolution of the virus.

Both Moderna and Pfizer have said that their respective BA.1 inclusive vaccines generated a better immune response against Omicron than their current shots that were designed for the original virus that emerged from China.

They have said their new vaccines also appear to work against BA.4 and BA.5, but that protection is not as strong as against BA.1.

The International Coalition of Medicines Regulatory Authorities, a group of global drug regulators that includes the FDA, will meet to discuss the issue on Thursday.