New data from the UK suggest that booster protection against symptomatic Covid caused by the Omicron variant wears off within 10 weeks.
There haven’t been enough severe cases of Omicron to calculate how well boosters protect against serious illness, but experts believe the syringes will continue to provide significant protection against hospitalization and death.
“It will take a few weeks before the effectiveness of Omicron against serious diseases can be assessed,” says the new report from the British health authority. “However, based on experience with earlier variants, this is likely to be significantly higher than the estimates for symptomatic diseases.”
In the weeks since Omicron was discovered, several studies have shown that the variant is adept at bypassing the antibodies produced after vaccination or infection with the coronavirus.
The new report from the UK, which included data on people who received the vaccinations with AstraZeneca, Pfizer or Moderna, confirmed that the vaccines – both the initial two-shot series and the booster doses – were less effective and wore off faster against Omicron than against Delta.
In people who received two doses of the AstraZeneca vaccine, a booster dose of one of Pfizer and Moderna’s mRNA vaccines was 60 percent effective in preventing symptomatic disease two to four weeks after vaccination. After 10 weeks, however, the Pfizer booster was only 35 percent effective. The Moderna booster was 45 percent effective after up to nine weeks. (The AstraZeneca vaccine is not approved in the United States, but the Johnson & Johnson vaccine uses similar technology.)
In people given three doses of Pfizer, the vaccine effectiveness decreased from 70 percent one week after the booster to 45 percent after 10 weeks. Pfizer recipients who received a Moderna booster, on the other hand, appeared to do better; Her vaccination schedule remained up to 75 percent effective after up to nine weeks.
The report, which was based on an analysis of approximately 148,000 Delta cases and 68,000 Omicron cases, also included updated data suggesting that Omicron infections are less likely to result in hospitalization than Delta infections. The agency noted that the results should be interpreted with caution, since there have not been many Omicron cases in relative terms and the people who have contracted the variant may not be representative of the wider population.
The Biden government has encouraged all eligible Americans to get booster vaccinations while Omicron spreads.
In a recent interview with WCBS-AM, a New York radio station, Dr. Anthony S. Fauci, the country’s foremost infectious disease doctor, told officials to monitor the effectiveness of mRNA boosters against Omicron.
“I think it is premature, at least on the part of the United States, to talk about a fourth dose,” he said. Israel is considering giving its citizens a fourth chance.
Some scientists warn of a fourth syringe, noting that there is still no evidence that it is necessary and that if too many doses are given, some immune cells may stop responding to the syringes.