WASHINGTON – The updated Covid-19 boosters from Pfizer-BioNTech and Moderna helped prevent symptomatic infections from the new XBB-related sub-variants, offering new evidence of how the vaccines perform against these fast-spreading strains, US officials said on Wednesday.
“Today we have additional evidence to show that these updated vaccines are protecting people against the latest Covid-19 variants,” Dr Brendan Jackson, head of the United States Centres for Disease Control and Prevention’s (CDC) Covid-19 response, told reporters in a briefing.
Released last autumn, the updated boosters target the BA.4 and BA.5 Omicron variants of the Sars-CoV-2 virus, which are no longer dominant. The now-dominant XBB-related sub-variants are derived from the BA.2 version of Omicron.
Lab studies had suggested that vaccine protection was lower against the XBB variants compared with prior variants, raising questions about how well the vaccines worked against these rising strains of the virus, Dr Jackson said.
For the study, researchers reviewed Covid-19 cases from Dec 1 through Jan 13, a period in which US circulation of XBB and XBB.1.5 increased. It showed that the updated vaccine helped prevent illness in roughly half of the people who had previously received two to four doses of the original Covid-19 vaccine, the CDC said.
The CDC said the updated vaccine worked similarly against BA.5-related infections and XBB/XBB.1.5-related infections.
It was 52 per cent effective at preventing infections from BA.5 and 48 per cent effective against XBB/XBB.1.5 among those aged 18 to 49. Effectiveness fell to 37 per cent against BA.5 and 43 per cent against XBB/XBB.1.5 among those aged 65 and older.
Dr Jackson said data to be released later on Wednesday shows the updated vaccine reduced the risk of death from Covid-19 by more than twofold, compared with vaccinated people who had not got the updated booster. The updated shot also reduced the risk of death from Covid-19 by nearly thirteenfold in those who are unvaccinated.
Study author Ruth Link-Gelles of the CDC said that overall, the vaccines cut the risk of symptomatic infection by about half on a population, but individuals see a different benefit based on their risk factors. She said the estimates are for symptomatic infection, which the CDC defined as one or more symptoms of Covid-19.
Given the findings, the CDC urged people to stay up to date on their recommended Covid-19 vaccines.
XBB.1.5 was estimated to make up nearly half of US cases in the week ended Jan 21, government data showed.
The CDC analysis came ahead of a meeting on Thursday at which outside experts to the US Food and Drug Administration are expected to discuss whether and how the US should offer the Covid-19 vaccine as an annual shot. REUTERS