HealthDay News — The ability of two-dose COVID-19 vaccines to protect against symptomatic infection by the omicron variant falls significantly short, but a booster shot provides considerable protection, according to the first real-world study of how effective vaccines are against the rapidly spreading new form of the coronavirus. The findings are preliminary and have not been peer-reviewed or published in a scientific journal.
Four months after their second dose of the Pfizer-BioNTech vaccine, people had only about 35 percent protection against symptomatic infection by omicron, which is significantly lower than against the delta variant, British government scientists said. But a third dose of the vaccine boosted that level of protection to about 75 percent, according to the study published Friday, The New York Times reported. Several months after vaccination, two doses of the AstraZeneca vaccine provided virtually no protection against symptomatic infection from omicron, but a booster dose of the Pfizer vaccine increased protection to 71 percent.
Despite their findings, the researchers said they expect that the vaccines will still provide an important defense against omicron-related hospitalizations and death, The Times reported.
Omicron cases in England are doubling every 2.5 days. By mid-December, omicron could overtake delta in the United Kingdom and, without any precautionary measures, cause COVID-19 cases to soar, according to government scientists.
A computer modeling study of England released on Saturday suggests that even in populations with high levels of immunity, omicron could cause significant societal disruptions and overwhelm hospitals, The Times reported. A person infected with omicron is about three times more likely than someone infected with delta to pass the virus to other members of his or her household, and a close contact of someone with omicron is about two times more likely than a close contact of someone with delta to become infected, according to the Health Security Agency in Britain.