The Centers for Disease Control has just released results from a head-to-head study of all three COVID-19 vaccines available in the U.S., and Moderna's comes out on top when it comes to effectiveness.

The study, conducted nationwide between March and August, looked at 3,689 vaccinated adults who were hospitalized with COVID-19, as well as checking for antibodies in the blood of 100 healthy volunteers. And while all three vaccines were found to offer "substantial" protection against severe disease and hospitalization, one of the three came out on top with a slight edge, as CNN reports. The Moderna vaccine was found to be 93% effective at keeping people out of hospitals, with the Pfizer vaccine being 88% effective.

"Among U.S. adults without immunocompromising conditions, vaccine effectiveness against COVID-19 hospitalization during March 11--August 15, 2021, was higher for the Moderna vaccine (93%) than the Pfizer-BioNTech vaccine (88%) and the Janssen vaccine (71%)," the CDC wrote in a weekly update.

"Although these real-world data suggest some variation in levels of protection by vaccine, all FDA-approved or authorized COVID-19 vaccines provide substantial protection against COVID-19 hospitalization."

The study also confirms a decline in effectiveness in the Pfizer vaccine after four months, which had been seen in an earlier study of 50,000 patients done by the Mayo Clinic Health System, released in August. Some experts have pointed to the higher mRNA dosing that was in Moderna's vaccine.

"Differences in vaccine effectiveness between the Moderna and Pfizer-BioNTech vaccine might be due to higher mRNA content in the Moderna vaccine, differences in timing between doses (3 weeks for Pfizer-BioNTech versus 4 weeks for Moderna), or possible differences between groups that received each vaccine that were not accounted for in the analysis," the CDC team writes.

Work by the CDC and its researchers, they said, will hopefully help "guide individual choices and policy recommendations regarding vaccine boosters."

Meanwhile, an FDA panel was meeting Friday to discuss possible booster shots for the Pfizer vaccine, and whether there is evidence of risks or benefits from boosters. Depending on what the FDA panel decides, the CDC will then have to make a recommendation about who should get the booster shots — which could include older Americans, front-line health workers, and the immunocompromised.

Back in August, we heard that the FDA was likely to recommend boosters for many after 8 months, but the debate continues. And here in the Bay Area, Santa Clara County has already begun giving booster shots to the immunocompromised.

In San Francisco, if you received the Johnson & Johnson shot, they are offering booster doses of either Pfizer or Moderna at SF General.

Update: The FDA panel has recommended against boosters for people 16 and older, saying that the vaccines continue to offer strong protection and evidence for the need for boosters is still slim. The CDC may still end up recommending boosters for some people.

Previously: Study: Moderna Vaccine Significantly Better Against Delta Than Pfizer

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