U.S. officials said on Wednesday (January 25) that updated versions of the new crown vaccine booster shots from Pfizer and Moderna helped prevent symptomatic infection with a new XBB-related subvariant strain, adding to the vaccine. The ability to fight these fast-spreading strains provides new evidence.
Dr. Brendan Jackson, chief of the COVID-19 response at the Centers for Disease Control and Prevention (CDC), told reporters at a press conference: “Today, we have additional evidence that these updated vaccines protect people.”
The updated vaccine booster, launched last fall, targets the BA.4 and BA.5 Omicron variants of the new coronavirus (SARS-CoV-2); is no longer dominant. The currently dominant XBB-related subvariant originates from the BA.2 version of Omicron.
Laboratory studies have shown that vaccines are less protective against the XBB variant than previous variants, raising questions about the effectiveness of vaccines against these ever-mutating strains, Jackson said.
For the study, the researchers looked back at COVID-19 cases from December 1 last year to January 13 this year; during this period, the transmission of the XBB and XBB.1.5 variants increased in the United States. The CDC said studies have shown that the updated vaccine helped prevent infection from the new coronavirus in about half of the people who had previously received two to four doses of the original COVID-19 vaccine.
The CDC says the updated vaccine is equally effective at preventing BA.5-associated infections as XBB/XBB.1.5-associated infections.
In the population aged 18-49 years, the effective rate of preventing BA.5 infection was 52%, and the effective rate of preventing XBB/XBB.1.5 was 48%. In people aged 65 and older, effectiveness dropped to 37% against BA.5 and 43% against XBB/XBB.1.5.
Although not reflected in the study, data to be released later Wednesday shows that getting the updated vaccine reduced COVID-19 deaths compared with people who were vaccinated but did not get the updated booster shot, Jackson said. The risk was more than doubled. Those who received the updated vaccine had a nearly 13-fold lower risk of dying from COVID-19 compared with those who had never been vaccinated.
Overall, the vaccines cut the risk of symptomatic infection in the population by about half, but individuals can respond based on their own risk factors, said Ruth Link-Gelles, an author of the CDC study. The benefits obtained are different.
Those estimates are for symptomatic infections, Link-Gellers said. Symptomatic infection is defined by the US Centers for Disease Control and Prevention as one or more symptoms after infection with the new coronavirus.
In light of the findings, the CDC urges people to get the recommended updated COVID-19 vaccine promptly.
XBB.1.5 infections are estimated to account for nearly half of U.S. cases in the week ending Jan. 21, government data show.
The CDC analysis comes ahead of a meeting on Thursday (Jan. 26) in which outside experts from the U.S. Food and Drug Administration (FDA) are expected to discuss whether and how the U.S. should contain the novel coronavirus. The vaccine is scheduled to be given once a year.
(This article is based on a Reuters report.)