If you're going to get a "supplemental" or "booster" shot in the coming weeks or months and you didn't originally get Moderna's mRNA vaccine, you may want to consider topping up with Moderna, according to a new study.

A large study of 50,000 patients in the Mayo Clinic Health System found that effectiveness of both the Pfizer and Moderna vaccines against Delta variant declines by the six-month mark, however the decline was far more significant among patients who received the Pfizer vaccine.

The study, which has not yet been peer-reviewed, found that effectiveness of the Moderna vaccine against COVID dropped from 86% in January 2021 — when the Alpha variant was more prevalent — to 76% in July, when the Delta variant was prevalent nationwide. Over the same period of time, effectiveness of the Pfizer/BioNTech vaccine fell from 76% to 42%, suggesting that the Moderna vaccine maintains stronger protection against the Delta variant over time.

Dr. Venky Soundararajan, who led the study and works for Massachusetts data analytics firm nference, concludes that individuals seeking booster shots — especially those who received the Johnson & Johnson or Pfizer shots initially — should likely seek out Moderna shots for better protection against the Delta variant, as Reuters reports.

Much as other data has suggested up to this point, the researchers found that both vaccines were still highly effective at preventing serious illness and hospitalization. But Moderna seems to win out when it comes to preventing infection at all, months out from one's shots.

Data out of Israel supports the new study as well. Researchers in Israel, where the vaccine rollout was much swifter than in the U.S. in December and January, found that among 34,000 fully vaccinated people — with the Pfizer vaccine — 1.8% had breakthrough COVID infections. And the odds of getting infected rose significantly after five months, they found, especially among those 60 years old and up. Most of the breakthrough infections, in fact, have been detected recently, as the vaccine's effectiveness has apparently faded.

The vast majority of these infections appear to be mild, and they resulted in very few hospitalizations, according to study coauthor Dr. Eugene Merzon of Leumit Health Services.

Related: If You Got the Johnson & Johnson Shot, SF General Will Give You a 'Supplemental' Pfizer or Moderna Shot

Photo: Ian Hutchinson