Serum antibodies induced by the Pfizer/BioNTech COVID-19 vaccine (BNT162b2, Comirnaty) neutralise the Omicron variant of SARS-CoV-2 after three doses, suggest preliminary laboratory studies.
The studies, announced by Pfizer/BioNTech, indicate that a third dose of their vaccine increases neutralising antibody titres 25-fold compared to two doses against the Omicron variant.
However, the companies stress that, because 80% of the virus spike protein is unaffected by Omicron’s mutations, ‘two doses may still induce protection against severe disease’.
“Our preliminary, first dataset indicate that a third dose could still offer a sufficient level of protection from disease of any severity caused by the Omicron variant,” said Dr Ugur Sahin, CEO and co-founder of BioNTech. “Broad vaccination and booster campaigns around the world could help us to better protect people everywhere and to get through the winter season.”
However, Pfizer chairman and CEO Albert Bourla was more specific, stressing that three doses of the Pfizer/BioNTech vaccine “remains the best course of action to prevent the spread of COVID-19”.
The two companies added that work was progressing on an adapted vaccine to tackle Omicron, which could be available by March 2022.
“We continue to work on an adapted vaccine which, we believe, will help to induce a high level of protection against Omicron-induced COVID-19 disease as well as a prolonged protection compared to the current vaccine,” said Dr Sahin.
Pfizer and BioNTech still expect to produce four billion doses of their vaccine next year, regardless of whether the original or adapted vaccine is required.
The Pfizer/BioNTech laboratory studies evaluated the effectiveness of their vaccine against Omicron by testing a panel of human immune sera obtained from the blood of those who had received two or three doses. Pseudovirus neutralisation tests assessed the levels of neutralising antibodies against both wild-type SARS-Cov-2 and Omicron spike proteins.
A third dose increased neutralising antibody titres against the Omicron strain spike by 25-fold, meaning that the neutralisation effects of three doses against the Omicron was comparable to that seen against the wild-type strain after two doses.
A third dose also strongly increased CD8+ T cell levels against multiple spike proteins including Omicron, which are believed to correlate with protection against severe disease.