If You Got This Vaccine, You May Be More Protected Against Delta

A new study says this vaccine could be more effective against the fast-spreading variant.

Vaccinations have helped millions of people in the U.S. build protection against COVID, but some vaccinated people can and will still get infected. Research has found that various factors affect how protective vaccines are, such as age, underlying conditions, and the infectiousness of emerging variants. The Delta variant has now taken over the U.S., leading many vaccinated people to worry about their chances of contracting this fast-spreading version of the virus. Fortunately, new science is showing that one vaccine in particular may make you even more protected from Delta.

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Researchers from the Mayo Clinic Health System recently conducted a study on more than 50,000 patients from January to July to determine the effectiveness of both mRNA vaccines against two variants, the previously-dominant Alpha and the now-dominant Delta. Their findings were released Aug. 8 as a preprint on medRxiv.

According to the study, Moderna's vaccine may be more effective against the Delta variant than Pfizer's vaccine. The researchers found that the effectiveness of Moderna against COVID infection dropped to 76 percent in July, once Delta was dominant. It was 86 percent effective earlier in the year when Alpha was the most common version of the virus in the U.S.

On the other hand, Pfizer's effectiveness during Delta's dominance dropped to 46 percent against infection from 76 percent during Alpha's reign. So while both vaccines are still protective, Moderna's effectiveness is significantly higher and less affected by the Delta variant.

According to the study, individuals vaccinated with Moderna were also about half as likely to experience breakthrough infections than those vaccinated with Pfizer. But the researchers say that several factors could "contribute to the observed differences in effectiveness" of both the vaccines, as they have different vaccination processes and formulation despite both being mRNA vaccines.

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On the other hand, the effectiveness of both vaccines did not decrease significantly from January to July in terms of hospitalization. During Alpha, Moderna was 91.6 percent effective in preventing hospitalization and Pfizer was 85 percent effective. As Delta rose in prevalence, the vaccines' protectiveness against hospitalizations decreased to 81 percent and 75 percent for Moderna and Pfizer, respectively.

Venky Soundararajan, PhD, chief scientific officer at data analytics company nference and lead researcher for the study, told Reuters that his study could suggest a Moderna booster shot may be necessary soon for anyone who got the Pfizer or Moderna vaccines earlier this year.

Moderna recently said it expects that people who received its two-dose vaccine will need a booster shot later this year to help maintain protection against new variants of the virus. "We believe a dose three of a booster will likely be necessary to keep us as safe as possible through the winter season in the Northern Hemisphere," Moderna President Stephen Hoge, MD, said Aug. 5, per The New York Times.

The U.S. Centers for Disease Control and Prevention (CDC) previously said that people in the U.S. will not need a booster shot so soon, but an advisory panel for the agency is meeting on Aug. 13 to review data and discuss considerations for booster doses.

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