A new study shows that when children get vaccinated against seasonal influenza, the entire community can benefit.
The study found that people living in communities where about 80 percent of the children were vaccinated against the seasonal flu were much less likely to contract seasonal influenza, even if they had not gotten vaccinated.
The study was conducted in 49 remote Hutterite farming colonies in western Canada that have limited contact with the surrounding communities. The results, announced March 9, offer clinical evidence that immunizing schoolchildren can be effective if preventing flu transmission to the wider community.
Mark Loeb of McMaster University in Hamilton, Ontario, led the study. The research was funded in part by the U.S. National Institute of Allergy and Infectious Diseases and by the Canadian Institutes for Health Research. Scientists from several other Canadian universities and St. Jude’s Children’s Research Hospital in Tennessee participated in the study published online March 9 by The Journal of the American Medical Association.
Although previous studies have demonstrated what scientists call “herd immunity,” none have been so incontrovertible, because they were done in less isolated places with more sources of flu passing through. Also, only one other study, done 42 years ago, immunized more than 80 percent of a community’s children, as this one did.
Success repeated in many separate communities with very high vaccination rates implies that the shots themselves— rather than luck, viral mutations, hand washing or any other factor— were the crucial protective element.
“This is quite a definitive study, and it took a Herculean effort,” said Dr. Carolyn B. Bridges, an expert in influenza epidemiology at the Centers for Disease Control and Prevention. “My hat’s off to them.”
To do his unique study, Loeb made “literally hundreds of calls” to 187 Hutterite communities in Alberta, Saskatchewan and Manitoba, asking them to join.
Like the Mennonites and the Amish, the Hutterites are descended from a 16th-century Swiss Protestant sect. They believe in adult baptism, refuse military service, speak a German dialect and dress in homemade black jackets and long skirts.
“People from different groups can be identified by the size of the polka dots on their bonnets,” Dr. Loeb said.
Although they frown on television and radio, Hutterites drive cars and modern tractors. More important from a medical point of view, they live in communities of up to 160 people, own everything jointly, attend their own schools, eat in one dining hall and have little contact with the outside world.
Each community governs itself, but, in Loeb’s words, “after one very with-it Alberta bishop recognized the study’s benefit to the rest of the world and backed it,” almost 50 communities voted to participate.
Hutterites have no religious objections to Western medicine, that very “with-it” bishop, John K. Stahl, 76, said in a telephone interview with The New York Times. While deliberately cut off, they perform acts of generosity— for example, many donate blood frequently.
Some do not vaccinate their children, but not for religious reasons. “Some families are herb-minded rather than drug-minded,” Stahl explained.
In 25 of the colonies that joined, all children ages 3 to 15 received flu shots in late 2008; in 24 others, they received hepatitis A vaccine instead. (Hepatitis was not studied, but to keep the investigators from knowing which colonies received flu vaccine, they had to offer placebo shots, and hepatitis shots do some good while sterile water injections do not.)
By June, more than 10 percent of all the adults and children in colonies that received the placebo had had laboratory-confirmed seasonal flu. Less than 5 percent of those in the colonies that received flu shots had.
There was a 60 percent “protective effect” for the whole community, the study concluded. It implies, Bridges said, that giving flu shots only to schoolchildren would protect the elderly just as well as giving flu shots to the elderly themselves.
The CDC would never recommend that, she cautioned, “because you still should vaccinate high-risk people.”