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A new analysis from the US Centers for Disease Control and Prevention has found that the protection conferred by SARS-CoV-2 booster vaccines begins to decline after about four months, the Wall Street Journal reports.

CDC researchers examined vaccine effectiveness among people who received two doses plus a booster of the mRNA-based SARS-CoV-2 vaccines from Pfizer and BioNTech and from Moderna during the Omicron wave. As their analysis appearing in Morbidity and Mortality Weekly Report shows, they found that vaccine effectiveness against urgent care or emergency department visits fell from 87 percent and 91 percent in the two months after that booster, respectively, to 66 percent and 78 percent by four months after being boosted.

The Associated Press notes that researchers have expected the protection boosters offer to decline, as protection also fell following initial vaccination.

Still, vaccine efficacy was higher among people who received boosters, the AP adds. "COVID-19 vaccine boosters remain safe and continue to be highly effective against severe disease over time," Kristen Nordlund, a CDC spokesperson, tells it.

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