ST. LOUIS — A study published by Washington University scientists sheds new light on the potential long-term strategy for vaccinating against the virus that causes COVID-19.
The study, published Monday in Nature, adds to the wealth of research on how the COVID-19 vaccines induce an immune defense. The researchers found that a COVID-19 vaccine that specifically targeted the omicron variant of the virus generated cells that fight the variant, as well as earlier strains.
"I think our paper makes a case that updating the vaccine is important," said Ali Ellebedy, an associate professor at Washington University and senior author of the study.
The study looked at 54 healthy adults who had never knowingly had COVID-19. All had received two doses of the original Pfizer or Moderna vaccines before the study began. One group was given a booster dose of the original Moderna vaccine. A second group was given an updated booster dose that targeted the beta and delta variants of the virus, and a third group was given an updated booster dose that targeted the omicron variant.
The immune response from the omicron-targeting vaccine prompted cells that would fight against both the earlier variants, and against omicron. As a result, Ellebedy said, it's possible that future booster doses may not need to include the formulation that was made to target the earliest strains. They might only need to include a formulation that targets the newest variants.
"Our data suggests that a booster based on the latest variant would be enough to engage the memory cells, and induce new ones," Ellebedy said.
The researchers not only looked at blood samples, they also took samples from some of the participants' lymph nodes and bone marrow. It's a more difficult and labor-intensive study design, Ellebedy said, but offers a clearer look at the patients' immune responses. By looking at the lymph nodes, researchers can not only learn about how well the vaccines work, they can also make predictions about how long the benefits will last. The Washington University researchers started using this method two years before the pandemic hit, in 2018, originally with a focus on the annual flu shot.
Ellebedy noted that the study participants were all healthy, young adults. The findings might look different for children, seniors, or people with chronic health conditions that compromise their immune systems.
The U.S. has not recommended an additional booster dose for adults since the updated, omicron-targeting vaccines rolled out. It will be important to reach a decision about whether to recommend another booster before autumn, Ellebedy said.
Over the course of the COVID-19 pandemic, health experts have stepped up precautions ahead of the colder months. The first two winters of the pandemic, especially, brought devastating surges in the U.S. Plus the colder, dryer air typically makes it easier for viruses to spread, and pushes people to spend more time gathered indoors.
"I think the answer to that question will really depend on how the virus is evolving," Ellebedy said. "I think the efforts to track the evolution of the virus are really critical here."
The study was funded by the National Institutes of Health and Moderna.
