ATLANTA — Teens should get a booster dose of the vaccine for bacterial meningitis because a single shot doesn’t work as long as expected, a federal advisory panel said Wednesday.

The vaccine was initially aimed at high school and college students because the disease is more dangerous for adolescents and can easily spread in crowded conditions, like dorm rooms. Three years ago, the Advisory Committee on Immunization Practices said the vaccine should be offered to children ages 11 and 12. They believed the shot was effective for at least 10 years.

But the panel was told Wednesday that studies show the vaccine works for less than five years.

The committee debated adding a booster shot or simply push back the timing of the single dose to age 14 or 15. In the end, they voted for a booster dose at age 16, concluding it would be easier and less confusing to add a second dose after five years.

The 6-5 vote for a second shot was an unusually close vote for the panel.

The committee also recommended that people 65 and older who are around infants get vaccinated against whooping cough to help prevent its spread. They were reacting to an outbreak of whooping cough this year in California. Ten infants have died; nine were too young to be fully vaccinated against the contagious disease. Whooping cough vaccine is not currently recommended for the elderly.

The vaccine group provides advice to the Centers for Disease Control and Prevention. The CDC and the U.S. Department of Health and Human Services usually adopt the panel’s recommendations and sends the advice to doctors and the public.

However, the meningitis booster shot recommendation may not be adopted quite so easily. A Food and Drug Administration official, Norman Baylor, said more studies about the safety and effectiveness of a second dose of the vaccine are needed.

Some wondered if it was even necessary to make such a decision. Cases of bacterial meningitis are at historic lows, and a survey of more than 200 colleges and universities — representing more than 2 million students — in the last academic year found 11 cases of bacterial meningitis and three deaths.

“I’m not terribly worried about emergent disease,” said Dr. James Turner, head of student health at the University of Virginia. He is a liaison to the panel for the American College Health Association.

But during a public comment session, several people made passionate pleas to keep an initial dose at 11 and 12, and add a booster if necessary. A 25-year-old man told of how his legs and hands were amputated after a bacterial meningitis infection when he was 14.

“Why would we want to go backward?” said Nicholas Springer, of New York City.

A CDC expert, Dr. Amanda Cohn, told the panel that some studies have shown the vaccine’s effectiveness dropping off significantly within a few years. A small study of one vaccine, Menactra, found the vaccine was about 95 percent effective the first year but dropped to under 60 percent in patients two to five years after they were vaccinated.

The vaccine isn’t cheap. One vaccine, Sanofi Pasteur’s Menactra, was first licensed in 2005 and costs about $90. Another, Novartis’s Menveo, was licensed this year.

The vaccine is designed to prevent bacterial meningitis and an associated bloodstream infection. The infection can cause swelling of the membranes covering the brain and spinal cord.

Though the disease is fairly rare in the United States, those who get it develop symptoms quickly and can die in only a couple of days. Survivors can suffer mental disabilities, hearing loss and paralysis.

The bacteria is spread by coughing, sneezing and kissing, and most cases occur in previously healthy children and young adults.

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Online:

Vaccine panel: http://www.cdc.gov/vaccines/recs/acip/