Pfizer and BioNTech announced Tuesday that they have started a clinical trial testing a modified Covid-19 vaccine to protect against the supercontagious omicron variant of the coronavirus.
The drugmakers said they aim to enroll up to 1,420 healthy adults ages 18 to 55 in the trial, which will evaluate whether the omicron-specific vaccine is safe and generates a strong immune response.
The participants will be divided into three groups — fully vaccinated, fully vaccinated and boosted, and unvaccinated — which will determine whether they receive one, two or three doses of the modified vaccine.
The companies also said they expect to launch a similar study in the U.S. testing the shot in those older than 55.
The Centers for Disease Control and Prevention released new research Friday that found that a booster shot of the current vaccines provides robust protection against severe illness from the rapidly spreading variant, which accounts for virtually all new cases in the U.S.
The CDC studies also suggested that existing boosters offered “significant protection” against both infection and symptomatic illness, although the protection was higher during the delta surge compared to the omicron surge.
While the existing vaccines can protect people against some of the worst outcomes of Covid, drugmakers have said they would continue to develop variant-specific shots in case they are needed.
John Moore, a professor of microbiology and immunology at Weill Cornell Medical College, said the modified shots could become important in a “worst-case scenario” in which the omicron variant mutates to become as lethal as the delta variant.
“That scenario is not impossible,” he said. “If it happens, the new variant would kill a lot of vaccinated people and change the face of the pandemic for the worse.”
In other words, the new trial could be seen as “an insurance policy,” he said.
Moore added that by the time the results from the trial are in, public health officials and outside experts should know more about the trajectory of the pandemic.
Will omicron remain the dominant variant, or will it become a minor contributor to the overall pandemic? Will another variant more closely related to the ones that appeared last year emerge?
“We may not know that answer any time soon, but in the end it’s relevant to whether and how an omicron-based vaccine will be useful,” he said.
This story was previously published on NBCNews.com.