Americans now have three options when choosing a COVID-19 booster shot, so who should consider swapping brands and who shouldn’t?

The Centers for Disease Control and Prevention (CDC) does not take a position on whether individuals should mix and match. The agency’s guidelines merely give people the option of using any approved or authorized vaccine, particularly if another brand is more convenient.

However, individuals first immunized with the single-shot Johnson and Johnson vaccine should probably switch to Pfizer or Moderna for their second dose, said UC San Francisco infectious disease specialist Dr. Peter Chin-Hong

“J&J was always number three in the medals count. They had lower protection from hospitalization. They had lower protection from symptomatic infection,” he said.

A small but influential study organized by the National Institutes of Health found J&J recipients produced significantly more antibodies when given an mRNA booster instead of a second dose of J&J.

The study examined every combination of the three vaccines with about 50 volunteers in each group. It found a Moderna booster elicited the largest immune response in J&J recipients, with a roughly 76-fold jump in antibodies compared to a four-fold increase from a second J&J shot. Pfizer produced a 36-fold increase.

However, there’s an important caveat to the study. The authors conducted their experiments with a 100-microgram dose of the Moderna vaccine, which is the standard dose for the first two shots. The actual authorized booster dose is only 50 micrograms.

The authors are now studying the impact of a 50-microgram dose of mRNA, but the smaller dose might narrow the gap between Modena and Pfizer. Pfizer uses a 30 microgram dose.

The bottom line for J&J recipients is that either mRNA vaccine is a good choice.

“I think most people would probably favor an mRNA vaccine after an initial J&J shot,” said Dr. Chin-Hong.

People who are prone to blood clots or heart problems and those undergoing cancer treatment should talk to their doctor about which shot is best.

Should Moderna or Pfizer recipients mix and match?

There are not many compelling reasons to switch from an mRNA vaccine to the J&J booster, except in cases where an individual had a rare allergic reaction to a vaccine ingredient, Dr. Chin-Hong said.

The NIH study showed a modest benefit of swapping one mRNA vaccine for another. Moderna recipients who crossed over to a Pfizer booster saw an 11.8-fold increase in antibodies compared to a 10.1-fold increase. Pfizer recipients who got a Moderna booster produced a 31.7-fold increase compared to 20.9-fold. (The Moderna booster was 100 micrograms, instead of 50.)

Those types of increases may make little real-world difference, experts said. Based on the results of other studies, the authors projected each of the aforementioned scenarios would result in protection of 90% or better.

“The difference between 20 times more and 30 times more is probably not significant from the body’s perspective. That’s just an amazing response, period,” said Dr. Chin-Hong. “At the end of the day, I think flexibility trumps everything. You can’t really go wrong by picking one or the other.”

Dr. Chin-Hong said your default choice should be the mRNA shot you previously got, but you might consider switching from team Moderna to a Pfizer booster if you’re particularly concerned about side effects.

The CDC released data Wednesday on about 275,000 booster doses through October 10. Those who got a Moderna booster reported higher rates of side effects like fatigue, muscle soreness, headache, and fever.

Still, both Pfizer and Moderna recipients generally reported fewer side effects after dose three than dose two.

This story was originally published by Derek Staahl at KGTV.