Pfizer COVID Vaccine Partly Protects Against Omicron Variant: Early Study

Omicron can evade vaccine protection, but past infection and vaccination elicits a strong immune response.

Pfizer COVID Vaccine Partly Protects Against Omicron Variant: Early Study

Early reports seem to suggest that the hypothesis that the new COVID variant, Omicron, can circumvent vaccine protection may very well be true.

A laboratory study in its early stages has found that the Pfizer COVID vaccine only provides partial protection against the new variant of concern.

The study authors also argue for a third booster dose to counter the loss of efficacy. However, experts have been reiterating the need to wait for more research before making conclusive statements about the variant, its nature, and the sweeping need for boosters.

On an optimistic note, the study also shows that the vaccine does protect against the variant with the head researcher Alex Sigal calling it “robust, but not complete,” in an online presentation.


Speaking of the Omicron variant in an interview, earlier this week, Michael Ryan, WHO emergencies director, commented, "the preliminary data doesn’t indicate that this is more severe. In fact, if anything, the direction is towards less severity.”

What the Study Found

Before we look at what it found, here are some key points to note about the study.

  • The study was conducted by the Africa Health Research Institute in Durban, South Africa.

  • It was a small one involving 12 participants of which 6 were fully vaccinated and 6 were both infected with COVID and then vaccinated.

  • The participants included 4 males of which 2 were infected with COVID and then vaccinated.

The researchers found that the six people who were only vaccinated produced a weaker antibody response as compared to the infected and vaccinated group, with five out of six participants in the latter produced strong responses.

Breaking down the study and its results in a twitter thread, Alex Sigal said, "this was better than I expected of Omicron. The fact that it still needs the ACE2 receptor and that escape is incomplete means it's a tractable problem with the tools we got."

The study authors also reiterated that natural infection followed by vaccination elicited the strongest immune response, even against the Omicron variant.

"Previous infection, followed by vaccination or booster is likely to increase the neutralization level and likely confer protection from severe disease in Omicron infection."
Study authors

In the Twitter thread, Sigel also said, "this is our first set of data and is not corrected for values going below the lowest dilution used - we present the raw fold change, which is likely to be adjusted as we do more experiments."

In the meantime, Pfizer and Moderna have announced that they are altering their COVID vaccines against the Omicron variant.

(Written with inputs from Bloomberg, and the New York Times.)

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