- Pfizer and BioNTech have begun enrolling patients in a study testing a new version of their COVID-19 vaccine specifically tailored to the omicron variant, a hyper-infectious strain of the coronavirus that has quickly become dominant in the U.S. and several other countries.
- The study will enroll up to 1,420 healthy adults between 18 and 55 years old and evaluate the shot either as a primary series or a booster in people who have received two or three doses of the original vaccine, which is known as Comirnaty.
- The trial, which represents a key test of the need for variant-specific vaccines, will test the safety and immune response of each regimen. The companies didn't say when to expect results, though Pfizer CEO Albert Bourla reportedly said earlier this month that he expects an omicron-specific shot to be ready in March.
The speed with which Pfizer and BioNTech have brought a vaccine tailored to the omicron variant to human studies — just two months after the strain was identified by South African researchers — is a testament to messenger RNA technology, which can be quickly adapted to combat new viral threats.
That pace has positioned Pfizer and BioNTech to run a study just as infections from the highly transmissible variant are peaking in many parts of the U.S. and abroad. And that trial will yield crucial information not just for Pfizer, but all vaccine developers, as the results could help determine whether variant-specific shots are necessary.
Omicron has proven a challenging foe for vaccine and drug developers due to the large number of mutations to its spike protein, the target of each of the available COVID-19 shots as well as most antibody drugs.
Those mutations have enabled omicron to partially evade the immune response generated by vaccination, making more people susceptible to so-called breakthrough infections and triggering the largest wave of COVID-19 cases since the pandemic's start.
Omicron has also rendered most antibody drugs, which can keep infected patients out of the hospital, ineffective. The Food and Drug Administration notably just limited use of the two most widely used antibody drugs, from Regeneron and Eli Lilly, because they can’t neutralize omicron.
Those factors have increased pressure on vaccine makers to come up with new shots that can better thwart omicron. But it's unclear whether newer shots are truly needed. While vaccines from Pfizer and BioNTech, as well as Moderna, are less able to stop omicron infections, they’re still very potent at preventing severe disease, hospitalizations and death from COVID-19. Those effects are stronger for people who received a booster shot, which is also proven, at least for a few months, to reduce the likelihood of an infection.
Waves of omicron infections are also rising and falling quickly in a matter of weeks. It’s unclear, then, whether a shot specific to the variant will be needed by the time it's available, or if it'll be less effective than Comirnaty against other strains that already exist — like delta — or that could emerge in the future.
Those answers may come soon. Pfizer and BioNTech didn't say when they expect results from their trial, though Pfizer's Bourla indicated earlier this month that an omicron shot could be ready in March. And FDA officials have suggested the regulatory pathway will be much shorter for variant-specific versions of vaccines that, like Comirnaty, have already proven themselves. That means studies testing immune responses in hundreds of patients — like the one Pfizer and BioNTech are now running — may be enough to get a variant-tailored shot to market.
The trial will include three study groups. One group will receive up to two doses of the omicron shot three to six months after receiving two Comirnaty injections, while a second group that's already received three vaccinations will get either a fourth dose or the omicron shot as a booster. A third group that hasn’t yet been immunized will get three injections of the omicron vaccine.
The hope is the new shot will be as effective against omicron as Comirnaty was against other variants, but has a "longer duration of protection," BioNTech CEO Ugur Sahin said in a statement.
Moderna, meanwhile, expects to begin human testing an omicron-specific version of its vaccine early this year as well.