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Ongoing studies of immunity provided by available COVID-19 vaccines in the United States show that protection lasts at least six months, but many are asking if and when a booster vaccine might be necessary.

Given the impact of immunization recommendations on public health strategy, attention to the issue is warranted.

Booster shots are additional doses of vaccine following an initial vaccination series to extend the immunity they provide. Since the COVID-19 vaccines are novel — as is the virus they fight, SARS-CoV-2 — there is still no clear evidence for needing such shots at this time.

Currently, the Centers for Disease Control and Prevention does not recommend boosters for any COVID-19 vaccine, indicating that the need for and timing of COVID-19 booster doses have not been established. The CDC has also not offered recommendations on providing a booster shot of an mRNA vaccine, like Pfizer/BioNTech or Moderna, following a full one-dose series of the Johnson & Johnson vaccine.

It may be a while until those recommendations are made, according to Dr. Jim Conway, medical director, UW Health Immunization Program, and professor of pediatrics and infectious disease specialist, UW School of Medicine and Public Health.

“There is still so much to learn — how long immunity persists after vaccines, what kinds of reactions people might have with additional doses, and do the vaccines need to be updated for new strains of SARS-CoV2 — that it’s just too soon to know whether we will all need to have booster shots like we do for the flu,” he said.

However, there are scenarios in the future where booster shots could make sense to employ, Conway said. Examples could include boosters for select groups who have immune-weakening diseases such as HIV, organ transplants or cancer and who may not receive full protection from the initial COVID-19 immunization, or more widespread boosters if they are needed to respond to emerging variants.

For now, the priority needs to be continuing to provide vaccines to the unvaccinated – both locally and globally, Conway said.

“Once more countries around the world, and more communities in the United States, have been vaccinated with the available supply, it may be conceivable for high-risk populations, like people 65 years old and older, organ transplant recipients and perhaps healthcare workers to receive booster shots eventually,” he said.

UW Health follows guidance given by the CDC Advisory Committee on Immunization Practices once they are published in the Morbidity and Mortality Weekly Report, and since there are no recommendations published to provide boosters, UW Health does not offer them at this time.