The CDC’s Advisory Committee on Immunization Practices (ACIP) began its two-day deliberations on a Pfizer Inc.-Biontech SE booster dose for those ages 65 and older along with those at high risk for developing severe COVID-19 by hearing from William Gruber, senior vice president of vaccine clinical research and development at Pfizer. Gruber addressed concerns about booster recipients potentially developing myocarditis, a development he called “a rarity.”

Gruber said a third dose may provide protection for as much as a year or perhaps two years. The actual duration, he said, “will be driven largely by what we find as we gather data, so stay tuned.”

He noted Pfizer data of those receiving a third dose as having few adverse reactions, adding that those who are considered immunocompromised received the third dose. Boosters were authorized for immunocompromised individuals when there were no data for a booster in that population since they were excluded from trials.

He also mentioned that Pfizer has not conducted studies on using other vaccines, such as Moderna Inc.’s, as a combination in the booster dose though he mentioned there are sponsored studies elsewhere that are conducting such research and that he looked forward to reviewing any of those data.

Gruber also responded to questions about potential options in enhancing protection against COVID-19, such as lengthening the time between a first and second dose. He said he was reluctant to increase that amount of time, usually four to six weeks, as it may compromise the protection instead of enhancing it.

The ACIP committee also heard from Natalie Thornburg, CDC lead research microbiologist, who reviewed data showing degrees of protection are based on an individual’s level of immunity. She also mentioned that when a vaccinated person becomes infected, data show there is strong likelihood that they are infectious to others.