LOS ANGELES (AP) -- More hugs, fewer bugs. Holiday visits have become safer for grandparents thanks to a childhood vaccine that has dramatically curbed infections spread by kids, a new study finds.

For years, serious bacterial infections spiked among older adults around Christmas and New Year's, presumably because of contact with germy children. However, only one such spike has occurred since 2000, when the vaccine, Prevnar, came on the market, researchers report.

The vaccine is advised for children under 2. It fights common types of strep bacteria that cause illnesses ranging from mild ear infections to severe pneumonia and meningitis.

The vaccine has done "a terrific job of preventing transmission from children to adults not only around the holidays, but during other times of the year as well," said Dr. Matthew Moore of the Centers for Disease Control and Prevention.

Moore was part of the new research, reported in a letter to the editor in Thursday's New England Journal of Medicine.

Scientists studied illness patterns between 1995 and 2006. Infections surged among older adults every year during the holidays before the vaccine was available. Scientists suspected the increase came from contact with contagious kids during family gatherings. Women were most at risk, possibly because they were around kids more.

Infections, though, tapered off after the vaccine came out in 2000. The only exception was during the 2004-2005 holiday season; it's unclear why.

Many people carry the bacteria in their nose and throat without becoming sick. The illness is spread by direct contact with an infected person. Symptoms can include fever, chills, headache or ear pain.

Prevnar is the world's top-selling vaccine. It's made by Wyeth, which was acquired by Pfizer Inc. this year. The vaccine protects against seven of the most common strains of strep bacteria. A new version that defends against six additional strains is awaiting government approval.

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