The first real-world study of how vaccines hold up against the Omicron variant showed a significant drop in protection against symptomatic cases caused by the new and fast-spreading form of the coronavirus.
But the study, published by British government scientists on Friday, also indicated that third vaccine doses provided considerable defense against Omicron.
Government scientists on Friday also offered the most complete look yet at how quickly Omicron was spreading in England’s highly vaccinated population, warning that the variant could overtake Delta by mid-December and, without any precautionary measures, cause Covid-19 cases to soar.
Four months after people received a second dose of the Pfizer-BioNTech vaccine, the shots were roughly 35 percent effective in preventing symptomatic infections caused by Omicron, a significant drop-off from their performance against the Delta variant, the scientists found.
A third dose of the Pfizer-BioNTech vaccine, though, lifted the figure to roughly 75 percent.
Two doses of the AstraZeneca vaccine appeared to offer virtually no protection against symptomatic infection caused by Omicron several months after vaccination. But for those recipients, an additional Pfizer-BioNTech dose paid big dividends, boosting effectiveness against the variant to 71 percent.
Still, the study’s authors said they expected that the vaccines would remain a bulwark against hospitalizations and deaths, if not infections, caused by Omicron. And the researchers cautioned that even in a country tracking the variant as closely as Britain is, it was too early to know precisely how well the vaccines would perform.
That study was released alongside new findings about how easily Omicron is managing to spread. Someone infected with the Omicron variant, for example, is roughly three times as likely as a person infected by the Delta…