KUALA LUMPUR, Jan 26 – An mRNA Covid-19 booster dose can reduce the risk of hospitalisation from the Omicron variant by up to 90 per cent, according to new research released recently by the United States’ Centers for Disease Control and Prevention (CDC).
The three new studies from the agency support previous research — including studies in South Africa and the United Kingdom — indicating that available vaccines are less effective against Omicron than earlier versions of the coronavirus, but that boosters also significantly improve protection.
“Protection against infection and hospitalisation with the Omicron variant is highest for those who are up to date with their vaccination, meaning those who are boosted when they are eligible,” said CDC director Dr Rochelle Walensky during a White House Covid Task Force briefing last week, as quoted by NBC News.
The first CDC study looked at hospitalisations as well as emergency department (ED) and urgent care (UC) center visits across 10 states in the US, from August last year through early January this year.
It found vaccine effectiveness was best after three doses of the Pfizer or Moderna Covid-19 vaccines in preventing coronavirus-associated hospitalisations as well as ED and UC visits.
A booster mRNA Covid-19 dose was highly effective at preventing Covid-associated hospitalisation during the Omicron wave at 90 per cent, and was similarly effective at preventing ED and UC encounters at 82 per cent.
Protection from just two doses was lower, especially six months after the second dose.
The second study focused on Covid-19 infection and death rates in 25 states in the US from early April through the end of December last year.
People who were boosted had the highest protection against Covid-19 infection, both during the time Delta was dominant and when Omicron started to take over.
The third study, published in the Journal of the American Medical Association, also led by CDC researchers, examined people who tested positive for Covid-19 from December 10, 2021, to January 1, 2022, at more than 4,600 testing sites across the US.
Three shots of the Pfizer and Moderna vaccines were about 67 per cent effective against Omicron-related symptomatic disease compared with unvaccinated people.
Two doses, however, offered no significant protection against Omicron when measured several months after completion of the original series, researchers found.
Dr John Sanders, chief of infectious diseases at Atrium Health Wake Forest Baptist in North Carolina, said the findings should be “reassuring” for the public.
“We have these conversations all the time, at church, at football games, at basketball games: ‘Do I need that booster? Is it really going to help me?’” Sanders said, according to NBC News.
“Now I can cite three very large real-world studies that confirm what we are seeing all the time,” he said. “People who have gotten their booster are less likely to have a breakthrough, and when they do have a breakthrough, it’s much milder.”