Centers for Disease Control and Prevention advisers anticipate booster doses could be needed to increase COVID-19 vaccine effectiveness and prevent severe disease as the delta variant swarms the country, but in a Monday meeting, they did not endorse President Joe Biden’s plan to start offering boosters to a wide swath of consumers next month.

The Biden White House said earlier this month that beginning Sept. 20, booster shots would become available to all adults who were eight months past the date of their final vaccine. But that announcement was pending Food and Drug Administration and CDC advisers’ authorization. The Advisory Committee on Immunization Practices floated a more phased approach to boosters, starting with long-term health care residents and then essential front-line workers and older adults.

ACIP Chair Grace Lee said the committee would meet later to consider boosters for the rest of the general population but did not say when. A Pfizer-BioNTech representative told the working group the manufacturers would have data on their booster shots for all adults by the end of September at the earliest.

The committee’s COVID-19 vaccine working group insisted public health experts should focus on using booster doses to prevent severe disease in high-risk populations, and said preventing mild or asymptomatic disease may not be possible.

It’s not uncommon for a vaccine series to require several doses, and a vaccine that requires more than one dose does not necessarily mean it requires an annual booster, said Sara Oliver of the CDC’s National Center for Immunization and Respiratory Diseases. An extra shot after the initial dose series can create a “boost effect” that ups the amount of antibodies, B-cells and T-cells provided by the vaccine. More time between the initial dose or doses and a booster can help spur this effect.

Even though the committee is looking at booster shots, its members emphasized the top priority should continue to be the continued vaccination of unvaccinated individuals rather than boosters. The CDC advisory group also said booster policy needs to consider equity, access and global vaccine availability.Pfizer recommendation

The advisory group also voted 14-0 to again recommend the use of the Pfizer-BioNTech COVID-19 vaccine for use in people ages 16 and up. The committee had to review the vaccine again after the FDA granted the vaccine full approval last week, upgrading its status from emergency use authorization. In December 2020, ACIP made an interim recommendation for the use of the COVID-19 vaccine in adults ages 16 and older.

The group determined that the risk of serious adverse events following a COVID-19 is rare, and the benefits of the vaccine outweigh any risks.

John Su of the CDC said that 742 COVID-19 vaccine recipients reported heart inflammation such as myocarditis or myopericarditis as defined by the CDC. Of those who developed myocarditis or myopericarditis after receiving the Pfizer COVID-19 vaccine, the majority had recovered from symptoms at the time of follow-up. Many of these cases were milder than typical cases, committee members noted.

The risk of anaphylaxis after vaccination with the Pfizer mRNA vaccine is also low. The CDC recorded a rate of five cases per 1 million administered doses.

Benefits averted outweigh the risks, CDC data found. For every 1 million doses, the vaccine prevents nearly 12,000 hospitalizations and ICU admissions associated with COVID-19 in men and women ages 16-29.