The two initially recommended doses of the Pfizer COVID-19 vaccine are not enough to protect against the Omicron variant, but a booster dose of the shot just might be.

As part of preliminary studies conducted by Pfizer and BioNTech — the companies behind the vaccine — blood samples were collected from individuals who had received either two or three doses of the vaccine and tested. Results showed that there was a 25-fold drop decrease in antibodies against the new variant versus the earlier versions of COVID-19. The third dose, however, helps in the production of neutralizing antibodies that provide protection against the Coronavirus’ newest strain.

“Three doses against Omicron are almost equivalent to the two doses effectiveness we had against the … original variant,” Pfizer CEO Albert Bourla said Wednesday on NBC’s “Today” show. “You may need to go get the third booster faster, and that’s something that the health authorities should consider very carefully and make their recommendations. But clearly having two doses compared to nothing protects you way better than having nothing.”

Fully vaccinated individuals who have not taken the third dose, he added, may still be protected from severe disease.

“Although two doses of the vaccine may still offer protection against severe disease caused by the Omicron strain, it’s clear from these preliminary data that protection is improved with a third dose of our vaccine,” Bourla explained in a statement. “Ensuring as many people as possible are fully vaccinated with the first two-dose series and a booster remains the best course of action to prevent the spread of COVID-19.”

US health officials have pushed for people to get vaccinated and boosted since the development of the shots and even more during the emergence of the Omicron variant, which has already been detected in 19 U.S. states.

Pfizer and BioNTech, however, are still working on a vaccine that will specifically protect against the latest strain. “I’m not sure that we’ll need it because it’s one very likely scenario that the current booster will be enough to maintain protection, but if we need one, I’m sure we can make one and the good news is that we will have it by March,” Bourla told “Today.”