Moderna and Pfizer Share a Peek At Human Data For Bivalent Boosters

computer generated image of coiv-19 omicron virus along with vaccine.

Uma Shankar sharma / Getty Images

Key Takeaways

  • Moderna and Pfizer have released some preliminary human data about the efficacy of their updated COVID-19 bivalent boosters.
  • The Omicron-targeting bivalent boosters appear to elicit a strong immune response, but it’s not yet clear just how durable the protection will be.
  • The companies say they will share more data from clinical trials in the coming months.

Moderna and Pfizer have finally shared some clinical trial data about their updated bivalent booster shots. But it doesn’t tell us a whole lot. 

For more than two months, clinicians have been distributing booster shots designed to target both the original type of COVID alongside BA.4 and BA.5—the Omicron subvariants that now dominate U.S. COVID-19 cases.

But these vaccines were authorized based largely on mouse studies and data from older adults.

This week, both Moderna and Pfizer released early clinical trial data testing their bivalent boosters in humans.

Moderna’s data showed the immune benefits of getting a BA.1 booster shot—but didn’t look at the BA.4/BA.5 formulation that people across the U.S. are actually receiving.

Pfizer tested its BA.4/BA.5 formulation, but it only released data on its performance for a week after vaccination.

Moderna’s Data Suggests Update Boosters Work Better

Moderna reported data from a BA.1-targeting bivalent booster during a presentation at an infectious diseases conference Thursday.

This data comes from a trial of a bivalent vaccine that protects against both the original COVID-19 strain and BA.1, the first iteration of Omicron. The 90-day follow-up trial included 800 people.

Moderna hasn’t yet shared data on how its BA.4/BA.5-targeting bivalent booster performs in a clinical trial. But in lab tests, the company found the BA.1 bivalent shot elicited an antibody response to BA.4 and BA.5, as well as to other variants.

In people with a prior infection, the BA.1 bivalent vaccine boosted antibody levels nearly five-fold after a month, or nearly twice as much as the original booster. In people without prior infection, antibody levels increased nearly eight-fold.

Moderna’s human results show the value of having an update vaccine tailored to newer variants, even if they don’t answer the question of how well the currently-authorized bivalent boosters are actually working.

Over the course of three months, the company said people who got the bivalent booster had more and longer-lasting antibodies than those who got the original booster formula. The company also found that the immune protection from the original formula booster lasted for at least six months.

“While the only data for which we can share for six months is the original vaccines, imagine if your vaccine lasts for six months, it now lasts the winter season,” Jacqueline Miller, senior vice president of infectious diseases at Moderna, said in a press call.

The vaccine appeared to boost antibodies to a similar degree in older adults as in adults younger than 65 years. Side effects were similar to or less severe than those of a second or third dose of the original vaccine.

“As COVID-19 remains a global threat and a leading cause of death globally, this is an encouraging development, showing that a bivalent booster dose will offer important protection leading into the winter months,” Stéphane Bancel, Chief Executive Officer of Moderna, said in a statement.

Moderna said it expects data on how its BA.4/BA.5-targeting bivalent booster is performing in the real world later this year.

Pfizer’s Data Shows Promise in the Short-Term

Pfizer, meanwhile, has shared preliminary data how well its BA.4/BA.5 booster shot—which is available to anyone age 5 and older—performed in recipients one week after vaccination.

The data is an early report from a 900-person Phase 2/3 clinical trial that is still underway.

Pfizer compared antibody levels in older adults who received a second booster shot of the original vaccine to those whose second booster was the new BA.4/BA.5 bivalent vaccine. The company also compared the immune responses of 40 people aged 18 to 55 to the older adults who received the bivalent vaccine.

The data showed a substantial increase in Omicron BA.4/BA.5 neutralizing antibody levels, though the increase was more robust in the small group of participants under age 55. And the bivalent booster was better at increasing antibody levels than the original vaccine formula.

In a few weeks, Pfizer plans to release data on how the bivalent vaccine performed a full month after vaccination.

“While we expect more mature immune response data from the clinical trial of our Omicron BA.4/BA.5-adapted bivalent vaccine in the coming weeks, we are pleased to see encouraging responses just one week after vaccination in younger and older adults,” Albert Bourla, Chairman and Chief Executive Officer of Pfizer, said in a statement.

What About Novavax?

On Wednesday, the FDA granted Novavax emergency use authorization to administer its vaccine as a booster dose for adults. Unlike Moderna’s and Pfizer’s versions, the Novavax booster uses the original formula and does not specifically target Omicron.

A Novavax booster is recommended only for people who can’t or won’t get one of the mRNA options. It can also only be given as a first booster—people who have already had one or more boosters must opt for a Moderna or Pfizer shot.

Are the Bivalent Boosters Enough for the Winter Ahead?

The updated bivalent boosters were designed to protect against Omicron subvariants BA.4 and BA.5—the variants which are still responsible for most of the U.S. cases. Researchers have predicted that the variants that Americans are likely to face in the fall and winter will also be spin-offs of Omicron.

New Omicron variants, including BQ.1, BQ.1.1, and BF.7, are gaining momentum over BA.4. It’s not yet clear just how well the bivalent boosters will protect against these new variants.

In the meantime, Miller said she is hopeful that immunity from the updated boosters will provide enough protection for the coming months.

“If we can get through the winter season and actually follow participants for longer than six months without there being another recommendation for a booster dose, we should see that immunity actually lasts much longer,” Miller said. “It’s a question of whether that immunity is matched to what is actually circulating.”

What This Means For You

If you are seeking a booster shot in the U.S., you will no longer have the option to get the original vaccine formulas from Moderna and Pfizer. Depending on what is available at the site where you get you vaccine, you may have the option of the bivalent Pfizer, bivalent Moderna, or original Novavax vaccines.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

By Claire Bugos
Claire Bugos is a health and science reporter and writer and a 2020 National Association of Science Writers travel fellow.