Originally Published: 28 JUN 22 17:27 ET

Updated: 29 JUN 22 06:56 ET

By Jen Christensen, CNN

(CNN) -- The US Food and Drug Administration's independent Vaccines and Related Biological Products Advisory Committee voted Tuesday to support recommending inclusion of an Omicron-specific component for a Covid-19 booster vaccine.

Twenty-one voting members of the FDA's independent committee voted on the question:

"Does the committee recommend inclusion of a SARS-CoV-2 Omicron component for COVID-19 booster vaccines in the United States?"

Nineteen of the members voted yes, two voted no.

"I voted in favor of Omicron because I think it's important to broaden immunity," said Dr. Wayne Marasco, a professor of medicine with the department of cancer immunology and virology Dana-Farber Cancer Institute Harvard Medical School. "I will say that I was pretty impressed today that we can do better."

"I think this is a step in the right direction, but we have to reevaluate this as we move forward," he added.

The committee felt that a modified vaccine would offer broader protection to match the coronavirus strain that is in circulation now.

Two Omicron subvariants, BA.4 and BA.5, are now dominating transmission of Covid-19 in the United States, according to the US Centers for Disease Control and Prevention.

Future US Covid-19 vaccines will be different

This means that the Covid-19 vaccine people in the US will get in the future will be different. The committee does not determine how, and the committee was not asked to vote on what sublineage to include or whether the booster should be monovalent vaccine or a bivalent vaccine, which would include two strains.

Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, said there will be a conversation going forward to determine who needs another booster and what that booster will look like. Marks noted that a bivalent vaccine targeting the BA.4 and BA.5 Omicron subvariants seemed to be the preference of the committee.

When the FDA's independent vaccine advisers had met in April, they agreed that they had to develop a framework for how the country can keep up with the evolving virus with an appropriate vaccine strategy.

The FDA said in May that the "new normal" may include an annual Covid-19 and flu shot for people in the fall. Cases are expected to rise again in the fall and winter.

Challenging work ahead

Dr. Arnold Monto, the acting chair of the independent vaccine advisers committee, suggested determining what goes into the booster will not be easy.

"I think we have done the best we can in a difficult situation with imperfect data and inability to say what is going to follow what looks like Omicron 4 or 5 wave," said Monto. "We've looked at the options that are available and come up with a set of recommendations and some advice that FDA can follow."

Moving forward to create a vaccine to best fight a virus that changes quickly is "uncharted territory"

"Looking in the past doesn't help us a great deal to look in the future for this virus which has baffled a lot of us and made predictions almost irrelevant," Monto added.

What the companies are working on

Current Covid-19 vaccines are based on the coronavirus that emerged in late 2019, but Pfizer and Moderna have been working on updated versions of the vaccines. The current vaccines are not as effective against the variants in circulation.

Moderna presented details about its bivalent Covid-19 vaccine booster, mRNA-1273.214, which the company said elicits "potent" immune responses against the Omicron subvariants BA.4 and BA.5.

Moderna's bivalent booster vaccine candidate contains components of both Moderna's original Covid-19 vaccine and a vaccine that targets the Omicron variant.

Pfizer/BioNTech also presented data to the committee that showed that their two Covid-19 vaccine boosters targeting Omicron showed a substantially higher immune response than its current Covid-19 vaccine. Preliminary lab studies suggest the vaccines could neutralize the Omicron BA.4 and BA.5.

Another vaccine maker, Novavax, has committee support for emergency use authorization in the United States, but the FDA has not yet authorized its vaccine. Novavax told the committee that it has been developing variant-specific updated versions of its Covid-19 vaccine as well as a Covid-19 and flu combination vaccine.

Broader is better

The World Health Organization told the independent committee of vaccine advisers Tuesday that the vaccination strategy going forward should probably be based around a vaccine that would offer as broad a kind of protection as possible, rather than just continuing with the vaccines that were made against the original strain that is no longer in circulation.

"I still think there's value in increasing the breath of immunity and I will reiterate that we're not trying to match what may circulate," said Dr. Kanta Subbarao with the World Health Organization Collaborating Center for Reference and Research on Influenza and the University of Melbourne. "It is not so much to match what is likely to circulate because there's so much uncertainty about the trajectory of this evolution."

Including Omicron in a future vaccine would help because Omicron is the most distinct of the variants of concern that have emerged she said, but a standalone vaccine that would match just Omicron would not likely be broad enough to protect against other variants going forward.

"We're trying to increase the breadth of the immune response without losing the benefit from the index vaccine that's performed so well," she added.

"We simply don't have enough information on any of the other variants, but I could make a strong case based on our experience with influenza that using a virus to boost that is antigenitically as far as possible, is a better strategy than something that is partway there," she added.

The longer that Omicron is the dominant variant circulating in the world, the odds are that whatever comes after it will come from Omicron.

"At least that's a realistic possibility," Jerry Weir, director of the Division of Viral Products in FDA's vaccine research office, told the committee.

Future Covid-19 vaccine strategy

Going forward, as the committee determines how to create a process for the future if people will need regular Covid-19 boosters, members agreed that there needed to be better central coordination on studies and on what the plans should be going forward.

"Without such a plan, we're going to be playing Whack a Mole as this virus evolves, because it's going to continue to evolve," said committee member Dr. Bruce Gellin, chief of global public health strategy with the Rockefeller Foundation.

"We'll get better at this, but we still need to get ahead of it," he said.

Weir, with the FDA, tried to help the committee keep what they have accomplished in perspective.

"I think we've made enormous progress in this whole endeavor over the last few months, but I'll remind you that the sort of parallel track of influenza strain selection, which works very well, was a process that was honed over many, many years and so we probably have quite a bit of work. This is a different virus. We have a lot of work to do on the strain selection process for Covid vaccines."

Several committee members also were concerned about the lack of data concerning what should go into future pediatric vaccines.

"In terms of extrapolating available data, I am very hesitant to extrapolate that from adults into children," said committee member Dr. Archana Chatterjee, who is dean of Chicago Medical School. "I think the pediatric studies need to be done and they need to be done now."

Following the VRBPAC vote, the FDA will rule on the updated vaccine. Next a panel of independent experts that advise the CDC will take a closer look at the available data and make a recommendation, and the head of the CDC would decide if they should sign off on it.