The vaccine for Omicron looks promising, says Pfizer, but in the meantime, the booster remains the best shot at avoiding infection.
Early data indicate 2 things about the Omicron variant of COVID-19: That it causes less severe symptoms than earlier strains of SARS-CoV-2 (most notably Delta, which health systems still deal with), and that it possesses a greater ability to avoid neutralizing antibodies.
About the latter, Albert Bourla, the CEO of Pfizer, says that his company has an answer. In a television interview, Bourla said Pfizer’s COVID-19 vaccine for the Omicron variant will be ready in March.
The latest studies are showing that the COVID-19 vaccines have diminished efficacy against the Omicron variant. In a study published in Cell, 2 doses of an mRNA-based vaccine (Pfizer-BioNTech or Moderna) did not adequately neutralize Omicron.
Investigators from the Ragon Institute, MIT, and Harvard created a “pseudovirus” version of Omicron that mimicked its mutations. In the lab, they tested the efficacy of their pseudovirus against blood samples from 239 individuals vaccinated with an initial series of 1 of the 3 COVID-19 vaccines approved in the United States: a 2-dose regimen of Pfizer-BioNTech or Moderna, or a 1-dose regimen of Janssen. The study group also included 70 individuals who received a third dose of an mRNA vaccine.
The investigators found that all 3 vaccines in their primary series produced little to no effective protection against Omicron. They did see potent neutralization against Omicron in those who received an mRNA booster dose.
At the University of Cambridge, investigators created pseudoviruses that carried key mutations found in the Delta and Omicron strain, and showed that the latter variant was more efficient at evading vaccine-induced antibodies, but that it may not infect the lungs in the same way as previous variants.
“Omicron’s mutations present the virus with a double-edged sword: it’s got better at evading the immune system, but it might have lost some of its ability to cause severe disease,” lead investigator Ravi Gupta, PhD, MPH, professor at the Cambridge Institute of Therapeutic Immunology and Infectious Disease, University of Cambridge, said.
Gupta and his collaborators tested their pseudoviruses against blood samples from vaccinated individuals who had received 2 doses of either the Pfizer-BioNTech or AstraZeneca COVID-19 vaccines.
They reported the new variant required around a 10-fold increase in the concentration of serum antibody to neutralize the variant as compared to the Delta variant. And, in the majority of individuals who were administered 2 doses of the AstraZeneca vaccine, they were not able to neutralize the virus. The investigators said the data were confirmed in live virus experiments.
Although the Omicron strain was shown to be better at evading vaccine-neutralizing antibodies in specific 2-dose vaccines, a silver lining was discovered when they applied a booster dose of the Pfizer/BioNTech vaccine to both groups.
“The Omicron variant appears to be much better than Delta at evading neutralizing antibodies in individuals who have received just two doses of the vaccine,” Gupta stated. “A third dose ‘booster’ with the Pfizer vaccine was able to overturn this in the short term, though we’d still expect a waning in immunity to occur over time.”
At the moment, public health strategy is for people to continue to get vaccinated whether it is the first series or booster doses.
Pfizer’s Bourla said the goal is to offer better protection against emerging variants, but for now, the booster dose appears to be the best way to prevent hospitalization and severe disease.
"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.
This article originally appeared in Contagion®.