Booster shots provide the best protection against the Omicron variant, three large new studies from the US Centers for Disease Control and Prevention have found.
The studies found vaccinated people who had received a Pfizer or Moderna booster shot were far less likely to face serious illness or death from Omicron, which now accounts for 99 per cent of infections in the United States.
Collectively the three studies examined millions of cases, hundreds of thousands of visits to emergency departments and tens of thousands of adult hospitalisations.
One study that examined nearly 88,000 hospitalisations from across 10 states between December and January, as Omicron became the dominant strain in the US, found getting boosted was 90 per cent effective at preventing hospitalisations.
That compared with just 57 per cent protection for those who had received two shots when the second dose was more than six months old.
A second study focused on Covid-19 case and death rates in 25 states from the beginning of April through Christmas. People who were boosted had the highest protection against coronavirus infection, both during the time Delta was dominant and also when Omicron was taking over.
The findings echoed studies in Germany, South Africa and the United Kingdom that indicate available vaccines are less effective against Omicron than earlier versions of the coronavirus, but still provide significantly improved protection.
“Data from other countries have also shown significant benefit of getting the booster, but this is really showing it in the US,” Akiko Iwasaki, an immunologist at Yale University, told the New York Times.
“These numbers should be very convincing.”
Fewer than half of eligible double-vaccinated Americans have received their booster shots.
The CDC recommends everyone 12 years and older get booster shots. Pfizer and Moderna recipients should get boosted five months after their second shot, or those who have had the one-shot Johnson & Johnson vaccine are recommended to get theirs two months later.
Agencies contributed to this report
