Study finds three doses of Pfizer vaccine can handle Omicron

pfizer vaccine omicron, COVID
© Michele D’Ottavio

New data suggests that the Pfizer and BioNTech vaccine, at three doses, is enough to stop the Omicron variant from creating severe COVID

At this moment, Pfizer is being offered alongside Moderna in Global North countries as a booster vaccine. The Omicron variant is global, as it is notably more transmissible than variants which came before it. Despite increased transmissibility, it so far appears to be less harmful to the lungs – which are devastated by previous variants, like Delta or Beta.

A study, done by Alexander Muik and colleagues at BioNTech, found that three doses of the Pfizer vaccine would be sufficient against the Omicron variant.

Previously, researchers at the Clalit Institute suggested as much as 80% increased protection with three doses of Pfizer – but not specifically tested against Omicron.

Professor Ben Reis, Harvard Medical School and not involved in this study, said: “To date, one of the main drivers of vaccine hesitancy has been a lack of information regarding the effectiveness of the vaccine. This careful epidemiological study provides reliable information on third-dose vaccine effectiveness, which we hope will be helpful to those who have not yet decided about vaccination with a third dose.”

How did the team test this?

In their tests, the team tried Pfizer against Wuhan, Beta, Delta and Omicron pseudoviruses. Pseudoviruses are not the actual virus themselves, but a lab-made construction that will test a vaccine. For instance, it is quite difficult to secure the Wuhan version of COVID now – since that time, it has mutated heavily.

They found that Omicron has a large number of spike and other mutations, confirming a longheld understanding that neutralising antibodies may fail to recognise the new form of the virus.

Looking at the data of 51 participants, the team found that two doses of Pfizer created 22-fold reduced neutralising titers in contrast to what those two doses can do against the Wuhan variant. When it came to the third dose, things looked happier. They found that the triple-hit of Pfizer was able to hold 23-fold increased neutralising titers, the equivalent of two doses against the original form of the virus.

“Further clinical trial and real-world data” to come

The data suggests that: “a third dose of BNT162b2 augments antibody-based immunity against Omicron, in line with previous observations that a third vaccination broadens humoral immune responses against VOCs.”

Writing their conclusions, the authors said: “Further clinical trial and real-world data will soon emerge to address the effectiveness of a third dose with BNT162b2 against COVID-19 mediated by Omicron.”

Read the full study here.


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