Two doses of the Pfizer/BioNTech vaccine may not be enough to protect against the novel Omicron coronavirus variant, but three doses are enough to neutralize it, the pharmaceutical companies said in a statement. This offers new hope to fight the mutant variant which, although has just been discovered, has the entire world on alert.

Pfizer chief executive Albert Bourla said “the best course of action” to prevent the spread of Covid-19 is to get as many people as possible vaccinated with two doses and a booster. It’s not exactly a new approach, but it could be the only way to get some protection against Omicron until (or if) new vaccines arrive. Two doses only offer a limited level of protection against the Omicron variant, with initial data suggesting protection improves with a booster shot, he added.

However, these results are only preliminary and Pfizer says they will continue gathering data and evaluating the “real-world effectiveness” of the vaccine. They are now working on a new vaccine specific for the Omicron variant, which they hope it will be ready for delivery in the next 100 days, following approval from regulatory agencies. 

Initial Omicron studies

Researchers in South Africa first identified the new Omicron variant in late November. Since then, teams have been racing to better understand its properties and the risks it poses. Preliminary data suggests that the variant is highly transmissible (spreading faster than the Delta) and that is can infect people who are immune to other COVID-19 variants. 

The new strain has been classified as a variant of concern by the World Health Organization, the fifth one to be given that category. Still, WHO’s Emergency Director Mike Ryan said earlier this week that there are no signs that Omicron could be better at evading vaccines than other variants, expressing confidence in the vaccines’ overall protection. 

Pfizer and BioNTech found an average 25-fold reduction in the neutralization ability of vaccines against the Omicron variant. This shows that two doses “may not be sufficient to protect against infection with the Omicron variant,” they said — although again, it’s still preliminary data.

Another study by researchers from South Africa also found that the Omicron variant partly escapes antibody neutralization given by the Pfizer vaccine. Nevertheless, the preprint study showed that previously infected and then vaccinated individuals are likely well protected. This would also be the case of those who get a booster shot. 

Health officials are urging people to get vaccinated and boosted as soon as possible. In the US, for example, the Centers for Disease Control and Prevention advise adults who have had the Pfizer and Moderna vaccines to get a booster six months after their second shot. A quarter of those who are vaccinated have received a booster in the US.

“Vaccines remain the best public health measure to protect people from COVID-19, slow transmission, and reduce the likelihood of new variants emerging. COVID-19 vaccines are highly effective at preventing severe illness, hospitalizations, and death. Scientists are currently investigating Omicron, including how protected fully vaccinated people will be,” the CDC wrote in a statement.