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Pfizer found that two-dose recipients exhibited a more than 25-fold reduction in neutralization titers against Omicron relative to wild-type.
Pfizer and BioNTech announced results from an initial laboratory study concerning the effects of the Pfizer-BioNTech COVID-19 Vaccine on the SARS-CoV-2 Omicron variant on Dec. 8, 2021. The study found that individuals who received two doses of the current COVID-19 vaccine exhibited a more than 25-fold reduction in neutralization titers against the Omicron variant.
However, while the vaccine showed reduced effectivity against the Omicron variant in individuals who received two doses, those who received three doses fared much better. The study found that those who received a third dose (i.e., a booster vaccination) neutralized the Omicron variant to levels comparable to those observed for the wild-type SARS-CoV-2 spike protein after two doses.
Additionally, the results found that a third dose strongly increased CD8+ T cell levels against multiple spike protein epitopes; this increase in T cell levels is considered to correlate with protection against severe disease. Compared to the wild-type virus, the vast majority of these epitopes remain unchanged in the Omicron spike variant.
“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 CEO, Pfizer, in a company press 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.”
The companies began development of an Omicron-specific COVID-19 vaccine on Nov. 25, 2021, the development of which will continue as planned in the event that a vaccine adaption is needed to increase the level and duration of protection against Omicron. These vaccines are planned to be ready for delivery within 100 days, pending regulatory approval.