Outside advisers to the U.S. Food and Drug Administration on Friday voted unanimously to recommend a second shot of Johnson & Johnson's COVID-19 vaccine to better protect Americans who received the one-dose vaccine. A special FDA vaccine 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 neutralizing antibodies it provokes compared to vaccines using mRNA technology from Moderna and Pfizer. On Thursday, the panel unanimously backed booster shots of Moderna's vaccine for Americans aged 65 and older and those at high risk. U.S. health agencies authorized Pfizer boosters last month. Separately, the Wall Street Journal reported on Friday that FDA is delaying its decision on authorizing Moderna's COVID-19 vaccine for adolescents to check if the shot could increase the risk of a rare inflammatory heart condition. U.S. health officials have been under pressure to authorize the additional shots after the White House announced plans in August for a widespread booster campaign pending approvals from the FDA and the CDC.