Protection against omicron variant ‘improved’ after three doses of Pfizer vaccine

ByKen Downey Jr.

Pfizer and BioNTech said Wednesday that two doses of their COVID-19 vaccine “may not” offer sufficient protection against the omicron variant of SARS-CoV-2, but a third dose appears to improve protection.

Perspective from Amesh A. Adalja, MD

The companies announced findings from an initial laboratory study that tested the sera of people who received two or three doses of the vaccine against wild-type SARS-CoV-2 and the omicron variant.

The Pfizer-BioNTech vaccine is still likely to protect against severe disease caused by the omicron variant, the companies said. Source: Adobe Stock.

According to a press release, the lab study showed that sera from participants who received two doses experienced, on average, a more than a 25-fold reduction in neutralization titers against omicron compared with the original virus 3 weeks after the second dose.

However, sera collected from people 1 month after receiving a third dose neutralized the variant to levels comparable to the wild-type strain after two doses, the companies said, and there were indications that two doses still protect against more serious infections.

“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,” Pfizer CEO Albert BourlaDVM, PhD, said in the release. “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.”

Pfizer and BioNTech last month began development of an omicron-specific vaccine, in the event a modified vaccine is needed. If needed, the companies said they expect it will be ready by March.

The omicron variant has been reported in more than 50 countries and in 19 American states. Preliminary data suggest the variant “might” cause less severe disease, but more information is needed, National Institute of Allergy and Infectious Diseases Director Anthony S. Fauci, MD, said Tuesday.

Following the emergence of omicron, the CDC recommended that all adults receive a booster dose of COVID-19 vaccine 6 months after a messenger RNA primary series or 2 months after a dose of Johnson & Johnson’s adenovirus vaccine.