A panel of independent experts advising the Centers for Disease Control and Prevention (CDC) plans to consider additional doses of COVID-19 vaccine in a small fraction of the population with weakened immune systems.
The Advisory Committee on Immunization Practices (ACIP) plans to convene on July 22 to discuss "clinical considerations for additional doses in immunocompromised individuals," according to a draft agenda posted ahead of the meeting. The National Institutes of Health defines immunocompromised patients as those with "a reduced ability to fight infections and other diseases," potentially caused by conditions like "AIDS, cancer, diabetes, malnutrition, and certain genetic disorders" or medicines or treatments like chemotherapy and organ transplants.
The CDC and Food and Drug Administration recently said fully vaccinated Americans "do not need" an extra dose at this time. The health agencies said the U.S. "is fortunate to have highly effective vaccines that are widely available" to eligible populations.
However, Dr. Jay Butler, deputy director for infectious diseases at the CDC, told reporters this week that researchers are concerned about older adults above age 75 who face the highest risk of severe COVID-19, and those with weakened immune systems, or immunocompromised individuals, some of whom don’t respond as well to vaccination.
Butler also said the CDC is "keenly interested in knowing whether or not a third dose may be associated with any higher risk of adverse reactions, particularly some of those more severe although very rare side effects," reiterating data suggesting local reactions and rare side effects occur more frequently after the second dose in two-dose regimens.
An ACIP meeting last month presented several studies suggesting immunocompromised individuals, who account for about 2.7% of the country’s population, mount a diminished protective immune response, even after two doses of vaccine.
For instance, 7-27 days after a second Pfizer dose suggested 75% protection against symptomatic COVID-19 among immunosuppressed patients, compared with 94% overall. The patients also saw less protection against infection at 71% versus 90% overall, after two Pfizer doses.
Separate findings suggested over half of some 30 organ transplant patients under study didn’t respond to a third dose of vaccine. Experts at the time said it was unclear whether additional doses would benefit this population, or other prevention measures, like monoclonal antibodies, could offer more protection.