Three vaccine doses protect against Omicron, according to Pfizer/BioNTech lab study

By Rachel Arthur

- Last updated on GMT


Related tags COVID-19 vaccine COVID-19 vaccine booster COVID-19 variants Pfizer BioNTech

Two doses of the Pfizer/BioNTech vaccine ‘may not be sufficient’ to protect against infection with the Omicron variant; but three doses of the vaccine neutralize the variant, according to a preliminary laboratory study released by the companies.

While only an initial study, it is the first data to indicate whether existing COVID-19 vaccines are likely to protect against the Omicron variant or not.

Meanwhile, Pfizer and BioNTech say a variant-specific vaccine could be ready by March should it prove to be needed to increase the level and duration of protection against Omicron.

Three doses gives same protection against Omicron as two doses against wild-type

The companies looked at sera obtained from vaccinated individuals one month after receiving the booster vaccination (the third dose of BNT162b2) and compared it to sera from those who had only received two doses.

Sera in the booster group neutralized the Omicron variant ‘to levels that are comparable’ to those observed for the wild-type SARS-CoV-2 spike protein after two doses.

Meanwhile, those in the two-dose group saw a 25-fold reduction in neutralization titers: ‘indicating that two doses of BNT162b2 may not be sufficient to protect against infection with the Omicron variant’.

However, as the vast majority of epitopes targeted by vaccine-induced T cells are not affected by the mutations in Omicron, the companies believe that two-dose vaccinated individuals may still be protected against severe forms of the disease.

“Although two doses of the vaccine may still offer protection against severe disease caused by the Omicron strain, it’s clear from these preliminary data that protection is improved with a third dose of our vaccine,”​ said Albert Bourla, Chairman and Chief Executive Officer, Pfizer. “Ensuring as many people as possible are fully vaccinated with the first two dose series and a booster remains the best course of action to prevent the spread of COVID-19.”

The companies will continue to collect more laboratory data and evaluate the real-world effectiveness of the vaccine against Omicron.

Laboratory study

Sera were collected from subjects 3 weeks after receiving the second dose of Pfizer/BioNTech's COVID-19 vaccine, or one month after receiving the third dose.

Each serum was tested simultaneously for its neutralizing antibody titer against the wild-type SARS-Cov-2 spike protein, and the Omicron spike variant.

The third dose significantly increased the neutralizing antibody titers against the Omicron strain spike by 25-fold.

Neutralization against the Omicron variant after three doses of the Pfizer-BioNTech COVID-19 vaccine was comparable to the neutralization against the wild-type strain observed in sera from individuals who received two doses of the companies’ COVID-19 vaccine: The geometric mean titer (GMT) of neutralizing antibody against the Omicron variant measured in the samples was 154 (after three doses), compared to 398 against the Delta variant (after three doses) and 155 against the ancestral strain (after two doses). 

Vaccine development to meet 100 day goal

Pfizer and BioNTech say they will continue with the development of an Omicron-specific vaccine, pivoting tech that has already been used to create variant-specific vaccines.

“The first batches of the Omicron-based vaccine can be produced and are planned to be ready for deliveries within 100 days, pending regulatory approval,”​ says a statement from the companies. “Pfizer and BioNTech have tested other variant-specific vaccines as well, which have produced very strong neutralization titers and a tolerable safety profile. Based on this experience the companies have high confidence that if needed they can deliver an Omicron-based vaccine in March 2022.”

The companies have also previously initiated clinical trials with variant-specific vaccines (Alpha, Beta, Delta & Alpha/Delta Mix) and data from these studies will be submitted to regulatory agencies around the world to help accelerate the process of adapting the vaccine and gaining regulatory authorization or approval of an Omicron-specific vaccine, if needed.

If an Omicron-specific vaccine is adopted, it will not change the company’s expected production capacity for 2022, which is estimated at four billion doses.

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