Vaccine advisers to the U.S. Food and Drug Administration voted unanimously Friday to recommend a booster dose of Johnson & Johnson's vaccine at least two months after people get the first dose.The FDA's Vaccines and Related Biological Products Advisory Committee voted 19-0 to recommend the extra dose for all recipients of the J&J Janssen vaccine, 18 and older. They asked to simplify the original question being posed by the FDA, which had asked the committee to say whether the data showed that waiting six months or longer after getting the first shot would provide an even stronger immune response.The FDA will now consider the committee's advice. Then the U.S. Centers for Disease Control and Prevention's vaccine advisers will be asked to consider it.Johnson & Johnson says studies have shown boosting at two or six months can bring that effectiveness up to 94% and it says its effectiveness does not wane over time in the same way that effectiveness from Pfizer's vaccine does.But the Johnson & Johnson vaccine has not been shown to be as protective as either the Pfizer or Moderna vaccines, noted VRBPAC chair Dr. Arnold Monto, a professor of public health and epidemiology at the University of Michigan. "So there is some urgency here to do something," he told the meeting. And the CDC's Dr. Amanda Cohn told the meeting that various studies suggested real-world efficacy of J&J's vaccine was anywhere between 50% and 68%."Regardless of whether or not there's been waning or this is the true effectiveness after a single dose, the effectiveness or protection of a single dose of the J&J vaccine is not equivalent to protection at this time with either two doses of an mRNA vaccine and certainly not in those groups who have now been authorized to receive a booster dose of an mRNA vaccine," Cohn said.Members of the committee said while there was not much data to show whether the efficacy of the Janssen vaccine was waning -- or was strong to begin with -- they agreed people should be given the opportunity for a booster. "I would say I agree a second dose booster is needed to boost immunity back to the 90-plus range," Dr. Archana Chatterjee, a pediatric infectious diseases expert at Rosalind Franklin University in Chicago, said before the vote.The FDA has already given EUA to a booster for Pfizer's vaccine for people who are six months out from their first two shots who are also either 65 or older or who are at least 18 and have a higher risk of severe disease because of pre-existing conditions or because of work or living conditions.And Americans are already flocking to get those boosters. Data from the U.S. Centers for Disease Control and Prevention show close to 5% of fully vaccinated people -- about 9 million people -- have received booster shots.On Thursday, VRBPAC members voted unanimously to recommend booster doses of Moderna's vaccine to the same groups.J&J's FDA booster recommendation is the first COVID-19 vaccine to be recommended for all recipients. Booster doses for Pfizer and Moderna were recommended for recipients 65 and up or those who may be immunocompromised.CDC vaccine advisers are now set to discuss which groups to recommend Moderna or Johnson & Johnson boosters to. Typically, shots can be administered once the CDC director signs off on the recommendation. CDC's Advisory Committee on Immunization Practices is scheduled to discuss boosters on Oct. 21.