Only in the upside-down world of COVID-19 can three equal two. Lab study results released Wednesday morning by Pfizer and BioNTech say it will take three doses of their vaccine to produce a similar level of neutralizing antibodies to Omicron as two doses produced against the original virus and subsequent variants.

Pfizer-BioNTech’s preliminary research agreed with a new South African study published Tuesday that found current vaccines produce far fewer neutralising antibodies against Omicron. Yet the vaccines, in their original dosages, should still help prevent Omicron-related hospitalization and death, according to the World Health Organization.

But Omicron and the booster could redefine the meaning of “fully vaccinated.”

“Really, there are only two ways about this, short of social distancing and putting yourself in a bunker and not living with anyone, period,” says Dr. Ulysses Wu, Hartford HealthCare’s System Director of Infection Disease and Chief Epidemiologist. “The two ways out of this pandemic are masking and vaccination, and boosters as well.”

After two-dose test results found the drop in neutralizing antibodies, Pfizer-BioNTech researchers said a third dose boosted those antibodies by a factor of 25. So far, Moderna and Johnson & Johnson have provided no data on the effectiveness of their vaccines against the new variant, first identified last month in South Africa.

“We have to remember that the vaccines work,” says Dr. Wu, “not only in the production of antibodies, but stimulation of our B and T cells, which are our second and third lines of defense. If you like football, it’s basically our linebackers and safeties at this point. So if they get through the defensive line, we still have our linebackers, we still have our safeties that are going to provide some sort of protection.”

The Centers for Disease Control and Prevention recommends people 18 and older get a booster six months after completing their two-dose Pfizer-BioNtech or Moderna series or two months after the single-dose Johnson & Johnson vaccine. You are not required to get the same vaccine type you originally received.