Updated Covid-19 boosters continue to offer substantial protection even against the fast-spreading XBB.1.5 subvariant


The updated boosters roughly halve a person’s risk of becoming ill with Covid-19, even from infections caused by the fast-spreading XBB.1.5 subvariant.

The studies, led by researchers from the US Centers for Disease Control and Prevention, are one of the first looks at how bivalent boosters have continued to work in the real world as evolution progressed. of the virus. The data shows that the boosters continue to offer substantial protection against the variants currently in circulation.

The near real-time data was collected by the Increased Community Access to Testing program, which administers Covid-19 tests through pharmacies. It includes results for adults tested at participating pharmacies from December 1, 2022 through January 13, 2023.

Of nearly 30,000 test results included in the analysis, more than 13,000 (47%) tested positive for Covid-19.

More people who tested negative had received an updated bivalent booster compared to those who tested positive.

The study results show that updated reminders are more effective for young adults.

For adults aged 18 to 49, boosters reduce the risk of contracting a symptomatic infection caused by the BA.5 subvariant by 52% and the risk of contracting an infection caused by XBB or XBB.1.5 by 49%. . For adults aged 50 to 64, the new reminders reduce the risk of getting sick with Covid-19 by 43% for BA.5 and 40% for the XBB subvariants. For people aged 65 and older, boosters reduce the risk of infection with symptoms by 37% and 43% for the BA.5 and XBB subvariants, respectively.

The study authors saw little evidence of waning effectiveness two to three months after people received their vaccines.

The study authors said these were only estimates of the ability of vaccines to protect people against an infection that causes symptoms such as cough or fever. They probably work even better against more severe outcomes like hospitalization and death.

“What we know from past experience is that vaccines generally protect better against more serious diseases. So these are estimates of symptomatic infection and we expect similar estimates of hospitalization and death to be higher,” lead study author Ruth Link-Gelles said Wednesday. senior epidemiologist at the CDC.

Link-Gelles cautioned that these vaccine effectiveness numbers are averages. Because everyone is unique in terms of underlying health, past exposure to the virus, and other factors, these estimates of vaccine effectiveness may not apply at the individual level. She said it’s important to think about them at the population level.

To expedite the study results to the public, the researchers used a shortcut to estimate which Covid-19 infections were caused by the BA.5 subvariant and which were caused by the novel recombinant XBB subvariant and its subvariant. -lineage XBB.1.5.

The test results use a series of probes, or markers, to identify a positive case. Some variants of the virus that causes Covid-19 have mutations in their spike protein that cause one of the test markers to fail. This is called S gene target failure.

In the study, test results that showed S gene target failure were considered an infection caused by a BA.5 subvariant. Those that were positive for the S gene target were considered to be caused by the XBB or XBB.1.5 subline.

Leave a Comment