Lots of youngsters on your street? Watch out: Flu may strike your community sooner and harder than it hits the hip singles neighborhood down the road. Flu-shot season begins this month, and for the first time vaccination is being pushed for virtually all children - not just those under 5.
It's a huge change, and one bolstered by provocative new evidence that children are key flu spreaders. Over four winters, Harvard researchers matched hacking adults' visits to Boston-area emergency rooms with Census data for 55 zip codes. Flu-like symptoms struck first and worst in the zip codes that were home to the most kids.
Every 1 percent increase in the child population brought a 4 percent increase in adult ER visits, researchers reported this summer in Annals of Emergency Medicine.
"The impact of kids and the flu is clear," says study co-author John Brownstein, an epidemiologist at Children's Hospital Boston. "It doesn't mean the areas without kids are protected from flu. It just means they experience flu later and at lower rates."
Any parent can attest that youngsters are germ factories. It takes years of nagging before they cover coughs and sneezes. Little ones tend to pick their noses. Even teenagers aren't great hand-washers. Crowded schools, preschools and day-care centers act as incubators.
Previously, flu vaccine was recommended for youngsters under 5, who can become dangerously ill from influenza. This year, the government is recommending that children from age 6 months to 18 years be vaccinated - expanding inoculations to 30 million more school-age children. While they seldom get as sick as the younger tots, it's a bigger population that catches flu at higher rates, so the change should at least cut missed school and parents' missed work.
And it could have the added benefit of protecting entire communities if less influenza virus gets passed around.
"We're all very enthusiastic and anticipate seeing an indirect benefit, but that's something we need to study and carefully watch," says Dr. Jeanne Santoli of the Centers for Disease Control and Prevention.
That cocooning effect could be especially important for people over age 65, who account for most of the 36,000 flu-caused deaths each winter - possibly because the flu vaccine simply doesn't work as well inside aged bodies as it does in the young. While flu vaccine protects 75 percent to 90 percent of young healthy people, some research suggests that protection may plummet to 30 percent among their grandparents. And while more seniors are getting vaccinated, sadly there hasn't been a corresponding drop in their death rates.
Still, some protection is better than none. So scientists urge older Americans to keep getting vaccinated even as they hunt improvements. Research is under way to see if higher doses or adding immune-boosting compounds helps.
But the kid connection is getting increasing attention. Helping to drive the new inoculate-all-children advice is "a belief that if you could do that, you would limit transmission" to the elderly, says University of Rochester flu vaccine specialist Dr. John Treanor.
There's no proof yet, he cautions. But there's mounting suggestive evidence:
-New York City's health department tracked emergency-room visits for five flu seasons, and found school-age children are among the first sickened.
-Earlier work by Boston's Brownstein and Dr. Kenneth Mandl had implicated preschoolers, finding that a spike in respiratory illness in the under-5 crowd predicts that about five weeks later, flu-related deaths among the elderly will peak. In their newest study, flu struck the earliest in zip codes with the most preschoolers.
-Carroll County, Md., gave free doses of the nasal vaccine FluMist to 44 percent of its elementary school students in 2005, and saw less absenteeism that winter than a neighboring county. More intriguing, Carroll County's unvaccinated high school students missed less school that winter, too, suggesting some community-wide protection. -Tecumseh, Mich., vaccinated 85 percent of school-age children just before the 1968 influenza pandemic, resulting in 67 percent less flu-like illness in that community than in a neighboring one.
Stay tuned: Brownstein's next study, paid for by the government, will track the community impact of vaccinating more school-age children.
EDITOR's NOTE - Lauran Neergaard covers health and medical issues for The Associated Press in Washington.