Pfizer Inc. /zigman2/quotes/202877789/composite PFE -0.63% and BioNTech SE /zigman2/quotes/214419716/composite BNTX -1.62% said results from an "initial laboratory study" showed that their COVID-19 vaccine neutralized the omicron variant of the coronavirus after three doses, or the full two-dose regimen plus a booster shot. The drug makers said those who received just two does of the vaccine showed, on average, a more than 25-fold reduction in neutralization against the omicron variant. The research is very preliminary. The companies did not say how many people they gathered sera from, and it was released in a news release, not a preprint or peer-reviewed medical study. "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 Pfizer Chief Executive Albert Bourla. "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's stock rose 0.4% in premarket trading and BioNTech shares shed 1.6%, while futures /zigman2/quotes/209948968/delayed ES00 -1.09% for the S&P 500 /zigman2/quotes/210599714/realtime SPX -1.04% rallied 0.5%.