New York - On Thursday, the panel unanimously backed booster shots of Moderna's vaccine for people aged 65 and older and those at high risk.
Outside advisers to the US Food and Drug Administration on Friday voted unanimously to recommend regulators authorise a second shot of Johnson & Johnson's Covid-19 vaccine to better protect Americans who received the one-dose vaccine.
The FDA's Vaccines and Related Biological Products Advisory Committee backed the shots for all J&J recipients aged 18 and older at least two months after their first dose.
The FDA is not bound to follow the advisory panel recommendations, but typically does.
After hearing presentations from J&J and FDA scientists, members of the advisory panel asked if J&J's single-dose vaccine should actually be considered a two-dose shot for everyone.
They pointed to the lower levels of virus neutralising antibodies it provokes compared to vaccines using messenger RNA (mRNA) technology from Moderna Inc and Pfizer Inc /BioNTech SE
"There is a public health imperative. What we're seeing is this is a group with overall lower efficacy than we have seen with the mRNA vaccine, and so there is some urgency to do something," said Dr. Arnold Monto, an epidemiologist at the University of Michigan's School of Public Health who chaired the meeting.
Once the FDA signs off on the boosters, the US Centers for Disease Control and Prevention will make specific recommendations on who should get the shots. CDC advisers are scheduled to meet to discuss the boosters next week.
On Thursday, the panel unanimously backed booster shots of Moderna's Covid-19 vaccine for Americans aged 65 and older and those at high risk of severe illness or occupational exposure to the virus.
The US health agencies authorised boosters of the Pfizer/BioNTech vaccine last month.
US health officials have been under pressure to authorise the additional shots after the White House announced plans in August for a widespread booster campaign pending approvals from the FDA and the CDC.