Moderna, Pfizer or J&J for a vaccine booster?

Some clinics offer vaccine choice, others don't

When the Centers for Disease Control and Prevention green-lighted mixing booster shot brands last week for the various COVID-19 vaccines, it said people who originally had one kind may choose another.

But is it better to mix or to match? And when you make an appointment or drop by your favorite drug store, will you really have your choice like it’s Coke, Pepsi or RC Cola? The CDC left those questions unanswered when it announced “eligible individuals may choose which vaccine they receive as a booster dose” and that the agency’s recommendations “now allow for this type of mix and match dosing.”

On the Bay Area vaccine hunters Facebook group, questions abound:

“Had two Moderna shots. Any advice for Moderna vs Pfizer as booster?”

“So Confused,” wrote another from a poster who had the Johnson & Johnson shot and a half-dose Moderna booster, wondering, “is it OK”?

Dr. Monica Gandhi, an infectious disease specialist at the University of California-San Francisco, said studies have shown that for those who had the J&J shot, a Pfizer or Moderna booster increases the immune response considerably. For the most part, Dr.

Michael Lin agreed. The associate professor of neurobiology and bioengineering at Stanford University who has long called for more information about whether the single J&J shot offers enough protection, tweeted that J&J recipients would be “best off” with the Moderna booster dose, followed by Pfizer and J&J.

For those who had the Pfizer or Moderna shots for their initial round of immunization, studies suggest a booster dose with any of the available U.S.-authorized brands will do, Gandhi said.

In the U.S., more than 105 million people have received the two-dose Pfizer vaccine, almost 70 million the two-dose Moderna vaccine, and 15 million the one-shot Johnson & Johnson vaccine, the CDC says. Nearly 11 million have received a Pfizer booster, 1.9 million a Moderna booster and 15,000 got a J&J booster.

Federal regulators authorized boosters for those who had the Pfizer or Moderna shots who are age 65 or older or 18 and up but at high risk due to other health problems or who live or work in settings that increase their exposure to the virus. They are eligible for the booster six months after their last shot.

Regulators also authorized a booster for anyone 18 or older who had the J&J shot at least two months ago.

The difference stems from the different technologies each vaccine manufacturer used to deliver genetic code that triggers an immune response. Pfizer and Moderna use “messenger RNA,” a new technology that delivers the genetic material in tiny fat droplets.

J&J and other COVID-19 vaccine manufacturers such as AstraZeneca use an older viral vector technology in which a neutered virus delivers the genetic material to cells.

Gandhi said four studies in the United Kingdom, Spain, Germany and the U.S. National Institutes of Health have shown that following a viral vector shot with an mRNA vaccine boost increases the immune response.

“I therefore strongly recommend a J&J vaccine be followed by an mRNA vaccine second shot,” Gandhi said.

In terms of the other booster combinations, she said the NIH study showed no increased rate of adverse effects in any of the combinations and good antibody boosting.

“So I would recommend ANY booster — J&J, Moderna, Pfizer — after an mRNA vaccine course,” Gandhi said, noting that would increase flexibility and access for those seeking boosters.

One added complication is that the Moderna booster is authorized at half the dose of the primary shot series, though for those with weak immune systems, it’s given at full dose and considered part of the primary vaccination.