CNN
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The latest boosters cut a person’s risk of getting sick with Covid-19 by about half, even for infections caused by the fast-spreading XBB.1.5 variant.
A study conducted by researchers at the U.S. Centers for Disease Control and Prevention is one of the first to look at how bivalent boosters continue to work in the real world as viruses evolve. It shows that the booster continues to provide substantial protection against currently prevalent variants.
Near real-time data was collected by the Increased Community Access to Testing program, which administers Covid-19 testing through pharmacies. Includes results for adults tested at participating pharmacies between December 1, 2022 and January 13, 2023.
Of the approximately 30,000 test results included in the analysis, over 13,000 (47%) were positive for Covid-19.
Those with negative test results received more recent bivalent boosters than those with positive test results.
Research results show that the updated boosters are most effective in young adults.
For adults aged 18 to 49, the booster reduced the chance of having a symptomatic infection with the BA.5 subtype by 52% and the chance of having an infection with XBB or XBB.1.5 by 49%. For adults aged 50 to 64, the new booster reduces the odds of getting sick with Covid-19 by 43% for BA.5 and 40% for the XBB subtype. For those aged 65 years and older, the booster reduced the probability of symptomatic infection by 37% and 43% for the BA.5 and XBB subtypes, respectively.
The study authors found little evidence of a decline in effectiveness two to three months after people were vaccinated.
The study authors said these were only estimates of how well vaccines protect people from infections that cause symptoms such as cough and fever. It works better for different results.
“What we know from past experience is that vaccines generally protect better against more serious illnesses. We expect similar estimates to be higher,” lead study author Ruth Link-Gelles, a senior epidemiologist at the CDC, said at a news briefing on Wednesday.
Link-Gelles cautions that these vaccine efficacy figures are averages. These vaccine efficacy estimates may not apply to individuals, as underlying health conditions, previous exposure to the virus, and other factors vary from person to person. She said it’s important to think of them at the population level.
To make their findings public, the researchers used shortcuts to determine which Covid-19 infections were caused by the BA.5 subvariant and which were caused by the new XBB recombinant subvariant and its XBB.1.5 substrain. estimated
Test results use a series of probes or markers to identify positive cases. Some variants of the virus that causes Covid-19 have mutations in the spike protein that render one of the test markers non-functional. This is called an S-gene targeted disorder.
In this study, test results showing failure of the S gene target were considered to be infections caused by the BA.5 subvariant. was thought to be