The US Food and Drug Administration's staff said on Monday that expert advisers would discuss the timing and populations for use of additional COVID-19 vaccine boosters doses in a meeting later this week.

A panel of independent advisers to the agency will also weigh on the role of the FDA in deciding the composition of COVID-19 vaccines.

US health officials in late March authorized a second COVID-19 booster dose of the Moderna MRNA.O and Pfizer PFE.N vaccines for people aged 50 and older, citing data showing waning immunity and the risks posed by Omicron variants of the virus.

The FDA's staff said on Monday that new variants of the virus are often more infectious, transmissible, and distinct from earlier virus strains.

"The accumulating data suggest that the composition of vaccines may need to be updated at some point to ensure the high level of efficacy demonstrated in the early vaccine clinical trials," FDA staff said in briefing documents ahead of the April 6 meeting.

The current process to select the make-up of the seasonal flu shot, where regulators pick the strain to use for the coming year's vaccines, may help guide the process for COVID-19 shots as well, the FDA's reviewers said.