A health care worker preparing a COVID-19 vaccine in Marin County. (Photo from Marin County Department of Health and Human Services)

Federal health officials announced plans Wednesday to offer COVID-19 booster shots to fully vaccinated people in an effort to fortify their immune response in the face of more contagious COVID-19 variants.

A group of public health and medical experts from within the U.S. Health and Human Services Agency issued a joint statement expressing their support for the administration of booster shots roughly eight months after full vaccination with the two-dose vaccines developed by Pfizer and Moderna.

While the two vaccines remain highly effective at preventing serious infections and death, the officials argued that preemptively boosting the immune response, particularly among people with weakened immune systems and other high-risk demographics like nursing home residents, would maximize protection against the delta variant and subsequent variants, which may could be even more potent.

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The group of federal officials includes Centers for Disease Control and Prevention Director Dr. Rochelle Walensky, Food and Drug Administration Acting Commissioner Dr. Janet Woodcock, U.S. Surgeon General Dr. Vivek Murthy and National Institute of Allergy and Infectious Diseases Director Dr. Anthony Fauci.

“Our top priority remains staying ahead of the virus and protecting the American people from COVID-19 with safe, effective, and long-lasting vaccines especially in the context of a constantly changing virus and epidemiologic landscape,” the group said in its joint statement.

Booster doses will also likely be necessary for those who have gotten or will get the one-dose Johnson & Johnson vaccine, but federal officials expect to have more data in the coming weeks since the J&J vaccine did not become available in the U.S. until March.

The formal approval of booster shots remains subject to safety and effectiveness evaluations by the FDA and a CDC advisory panel.

The CDC’s vaccination advisory panel already issued an approval of booster doses last week for people with weakened immune systems who are more likely to suffer so-called breakthrough COVID-19 infections because their immune response is not as robust as that of people with fully functional immune systems.

State public health officials have also given the go-ahead to booster doses for immunocompromised people after the Western States Scientific Safety Review Workgroup — which includes officials from Nevada, Oregon, Washington and California — issued its approval on Monday.

“As California continues to see an increase in COVID-19 cases and hospitalizations, it is critical we take action to protect immunocompromised people who are most vulnerable to severe disease,” California Department of Public Health Director and state Public Health Officer Dr. Tomas Aragon said Monday in a statement.

According to federal officials, booster doses will be made available starting Sept. 20 to people who received their second vaccine dose eight months prior or more.

“At that time, the individuals who were fully vaccinated earliest in the vaccination rollout, including many health care providers, nursing home residents, and other seniors, will likely be eligible for a booster,” the HHS officials said Wednesday.

The World Health Organization has pushed back on the federal government’s booster shot plan, arguing that people in non-wealthy nations around the world must be prioritized before considering additional doses in wealthy Western countries.

HHS officials acknowledged the need to make vaccines available in poor countries but argued that the U.S. has already committed to donate more than 600 million doses globally, plans to donate even more and that increases in vaccination are needed both domestically and abroad.

“Nearly all the cases of severe disease, hospitalization, and death continue to occur among those not yet vaccinated at all,” the officials said. “We will continue to ramp up efforts to increase vaccinations here at home and to ensure people have accurate information about vaccines from trusted sources.”