The New COVID-19 Shot Is Surprisingly Effective Against the Latest Variant

The latest COVID-19 vaccine offers good protection against the currently dominant strain of the virus, according to a new report in the MMWR, a journal published by the U.S. Centers for Disease Control and Prevention (CDC). It's the first effectiveness data for the updated vaccine, which was released last fall.

Using federal and pharmacy-reported data sets, the team of CDC scientists compared people's COVID-19 test results to their self-reported vaccination status collected from September 2023 to mid-January 2024. They found that the new vaccine was about 54% effective at protecting people from symptoms of COVID-19. In other words, the symptoms that prompted people to get tested were less likely to be due to COVID-19 and more likely to be something else among those who were vaccinated a week to four months before getting tested.

They further calculated that the vaccine was 49% effective at protecting against symptoms from the JN.1 variant, which now causes a majority of infections in the U.S.—even though the shot was designed to target a different version of the virus, the XBB.1.5 variant.

That part of the analysis was based on the fact that current SARS-CoV-2 lab tests look for three major genetic signatures of the virus, which most of the variants previously contained. JN.1, however, is missing one of them, which allows scientists to distinguish the JN.1 samples from those containing other variants.

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“This is, to my knowledge, the first vaccine effectiveness estimates available worldwide for JN.1,” says Ruth Link-Gelles, vaccine effectiveness program lead for COVID-19 and RSV at CDC, who led the analysis. “What these results show is that someone who got this vaccine would have an extra boost of protection against symptomatic infection from both the XBB variant that was common in the fall, as well as JN.1 which is circulating now.”

Her group plans to release more detailed data on the vaccine’s impact on emergency room visits, urgent care visits, and hospitalizations in coming weeks, but says these initial data on protecting against infections are encouraging. “The COVID-19 vaccine is looking a lot like the flu vaccine, where we see about 50% protection against influenza in a good year against both infections and hospitalizations,” she says. But any immunity, whether from vaccines or infections, wanes. Link-Gelles says additional data will show how long the protection lasts, especially against symptoms of the disease. (Previous research suggests that protection against severe illness is longer lasting.)

The results underscore public health advice to get vaccinated, especially for people at higher risk of complications from COVID-19, such as the elderly, pregnant people and those with underlying health conditions. “There is elevated COVID-19 activity all across the country, but still very low vaccine coverage, with 21% of people over age 18 receiving the latest vaccine and 41% of those over age 65,” says Dr. Manisha Patel, chief medical officer of CDC’s National Center for Infectious Respiratory Diseases. “These data show that really the time to get vaccinated is now.”