Pfizer and BioNTech say a Third dose of their Covid-19 vaccine neutralised the Omicron variant in lab tests but warned the two-dose regimen was significantly less effective at blocking the virus.

A third dose increased antibodies 25-fold compared with two doses against the Omicron variant, the companies said, according to the Wall St Journal. But two doses might still prove effective in preventing severe illness from Covid-19, because immune cells are able to recognise 80 per cent of parts of the spike protein that the vaccine targets.

The results boost the case for repeated boosters to maintain people’s immune defences against an evolving Covid-19, the companies said.

“This is very positive news that should make everyone even more motivated to get vaccinated” and get a booster, said Pfizer Chief Scientific Officer Mikael Dolsten.

The companies’ current vaccine will provide a strong defence against Omicron, especially if people get a booster shot, Dr. Dolsten said. He said the three-dose regimen could provide stopgap protection against Omicron until a new vaccine targeted directly at the variant would be ready if needed.

Health authorities in Australia, the US and other countries have urged eligible people to get a third dose even before these results.
“Go and get your third boost as soon as possible,” Dr Mikael Dolsten, Pfizer’s chief scientific officer, told The Associated Press.
“This is comforting and a very positive message that we now have a plan that will induce immunity that is likely to protect from infection, symptomatic illness and severe disease from now across the entire winter season.”
Pfizer and BioNTech tested blood samples taken a month after a booster and found people harboured levels of Omicron-neutralising antibodies that were similar to amounts proven protective against earlier variants after two doses.