Pfizer-BioNTech and Moderna on Monday said they are actively developing a Covid-19 booster designed specifically for the omicron variant—but health experts question whether omicron-specific doses will be necessary by their estimated completion in March.

Your top resources on the Covid-19 vaccines

Omicron-specific vaccines could be ready by March

As the omicron variant continues to spread—making up over 95% of new cases in the United States last week, according to CDC—vaccine manufacturers Pfizer-BioNTech and Moderna are working to develop omicron-specific doses of their Covid-19 vaccines.

Pfizer CEO Albert Bourla on Monday said the company has already begun developing an updated version of its Covid-19 vaccine. And according to Pfizer spokesman Steven Danehy, the company hopes to have "50-100 million doses of the [omicron-specific] vaccine available by late March/early April," the Washington Post reports.

"We [are] already starting manufacturing some of these quantities at risk," Bourla said, meaning that if they are not ultimately needed, Pfizer will absorb the costs.

Similarly, Moderna CEO Stephane Bancel on Monday said that the company was "working very actively" on a Covid-19 vaccine booster that protects against omicron. According to Bancel, Moderna's booster shot should enter clinical trials "very soon," at which point the company would make updates to additional components of the shot, if needed.

The company aims to have an omicron-specific shot available by this fall, in preparation for another potential winter surge next year, Bancel said.

"We are discussing with public health leaders around the world to decide what we think is the best strategy for the potential booster for the fall of 2022. We believe it will contain omicron," Bancel said.

"We need to be careful to try to stay ahead of a virus and not behind the virus," he added. "Given the long-term threat demonstrated by omicron's immune escape, Moderna will continue to develop an omicron-specific variant vaccine."

"The hope is that we will achieve something that will have way, way better protection particularly against infections, because the protection against the hospitalizations and the severe disease—it is reasonable right now with the current vaccines as long as you are having, let's say the third dose," Bourla said.

Moderna is also testing different vaccine formulations, including a combination shot that would combine a flu and Covid-19 vaccine.

Are variant-specific vaccines necessary?

Health experts have questioned whether omicron-specific vaccines, will be necessary, NBC News reports.

As Covid-19 cases and hospitalizations continue to reach record levels in the United States, there are troubling signs of omicron's ability to escape current vaccine immunity. And while omicron-specific vaccines could help curb current case levels, they may be ready too late.

Public health experts have warned that a vaccine carefully tailored to omicron could prove counterproductive in a fast-changing pandemic where new variants are constantly emerging. Former FDA Commissioner Scott Gottlieb previously warned "there's reason to believe" that vaccines specifically targeting one variant might not work against others. 

John Moore, a professor of microbiology and immunology at the Weill Cornell Medical College, said by the time the new doses are ready, "omicron will almost certainly have come and gone."

"Omicron infections abroad have spiked up and then back down very rapidly," he added. "In the [United States] the present huge surge is likely to be over sometime in February. And omicron is so different that a booster specific for that variant would not work well against the variants we have been more used to."

Similarly, Peter Hotez, who developed a low-cost Covid-19 vaccine called Corbevax with his colleagues at the Center for Vaccine Development at Texas Children's Hospital, separately agreed, saying a new global variant will likely be more prevalent by this summer.

"I think rather than focus on sequence-specific boosters, there's a need to improve the mRNA technology to make it more durable," Hotez said. "The sharp declines in the effectiveness of Pfizer-BioNTech versus omicron after just a few months creates new challenges."

Separately, Paul Offit, a vaccine expert at the Children's Hospital of Philadelphia, argued the United States shouldn't distribute an updated vaccine unless a variant emerges that evades protection against severe illness. According to Offit, the current Covid-19 vaccines have "continued to be very successful at protecting against severe disease."

Previously, Anthony Fauci, National Institute of Allergy and Infectious Diseases director, said that an omicron-specific vaccine was not necessary because "booster vaccine regimens work against omicron." 

Ultimately, "[t]he message remains clear: If you are unvaccinated, get vaccinated, and particularly in the arena of omicron, if you are fully vaccinated, get your booster shot," Fauci said. (Rowland, Washington Post, 1/11; Cerullo, CBS News, 1/11; Beals, The Hill, 1/10 [1]; Beals, The Hill, 1/10 [2]; Lovelace Jr., NBC News, 1/10)