Omicron Covid booster offers better protection against symptoms, CDC says

The first real data on the new omicron vaccines reveals that they are better at preventing symptomatic Covid infections than previous doses, the Centers for Disease Control and Prevention said on Tuesday.

The results reinforce messages from public health officials that the new vaccines, from Pfizer-BioNTech and Moderna, should provide people with the best protection against Covid this winter, according to the CDC report.

The new boosters from Pfizer and Moderna target BA.4 and BA.5, as well as the original strain of coronavirus, in a single dose.

The vaccine effectiveness of the new boosters isn’t “stellar,” said Dr. Ofer Levy, director of the precision vaccine program at Boston Children’s Hospital, noting that scientists would like to see a vaccine that blocks infections entirely.

But, he said, it’s “something” and surpasses previous doses of the original formulation.


The CDC findings are based on more than 360,000 symptomatic adults tested for Covid at pharmacies nationwide from September 14 to November 11, when the omicron BA.4 and BA.5 subvariants were the dominant strains in the United States. United.

People who received the updated booster shots after two or more shots of the original vaccine were compared to another group of people who received only two or more doses of the original vaccine. (Early iterations of the vaccine from Pfizer and Moderna only target the original strain of coronavirus identified in late 2019.)

When should you get the Covid booster?

The updated booster shots were more successful in preventing infections in all adult age groups, with higher vaccine effectiveness in people who waited longer to receive the updated booster, the CDC found. .

“It makes sense,” said John Moore, professor of microbiology and immunology at Weill Cornell Medical College. He noted that studies have shown that longer intervals between doses of the Covid vaccine can lead to higher antibody levels.

The CDC currently recommends that people 5 and older receive an updated booster at least 2 months after their last dose. People who have recently had Covid should wait until they have recovered from the disease and end isolation. But people may also consider delaying boosters for three months after infection, depending on risk factors.

The CDC study confirms earlier data from Pfizer and Moderna that suggested updated vaccines are better than the old formula. But because that data only showed immune responses seen in blood samples, scientists weren’t able to determine how the new vaccines actually worked in the real world.

Scientists eagerly awaited real-world data. Updated boosters from Pfizer and Moderna were cleared by the Food and Drug Administration in late August without human trial data — a move seen as risky by some, especially if the new vaccines later prove not to be. not be better than existing vaccines.

The CDC said its study had several limitations, including that vaccination status and medical history were self-reported and could be biased. Previous Covid infections may be underreported, the agency said, and low usage of updated reminders may have affected the results.

Dr. Celine Gounder, a senior researcher at KFF, formerly known as the Kaiser Family Foundation, and an infectious disease specialist, also noted that the CDC report looked at infections during the spread of the omicron BA.4 subvariants. and BA.5.

Newer BQ.1.1 and BQ.1 subvariants are on the rise in the United States, she said, and it’s unclear how updated boosters will work against these strains.

Levy agreed, saying matching vaccines to currently circulating strains is like “playing the mole.”

Still, he urged people to get vaccinated, saying the updated booster shots should provide a good level of protection against the new variants.

“We are not off the hook,” he said.

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