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Lifelong Immunity? With Vaccines, It Depends
by NANCY SHUTE
October 11, 2010
At 2:30 on a Tuesday afternoon, moms and babies are gathering at Angela Shogren's townhouse in Alexandria, Va. As the babies try to crawl across the basement floor, the moms talk about breastfeeding and lack of sleep. One issue keeps coming up: vaccines.
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Different Levels Of Immunity
It turns out that there are no simple answers to the question of whether natural immunity caused by exposure to a germ is better than the industrial version. "It varies from vaccine to vaccine," says Samuel Katz, an inventor of the measles vaccine and a chairman emeritus of pediatrics at Duke Medical School.
Protecting Against This Season's Flu
When the H1N1 flu pandemic peaked last fall, many Americans, and especially parents, were left confused and frustrated by the limited quantity of available vaccine. Last year's flu also left a wake of sick children, and many more pediatric deaths from flu than usual. Some 276 children under the age of 18 -- most of whom did not receive the vaccine -- died from H1N1 in the 2009-2010 flu season, double the number from the previous flu season.
This year, the Centers for Disease Control and Prevention has called for universal vaccination: all Americans over six months of age should be vaccinated, the agency said. Kids who received the seasonal flu or H1N1 vaccine last season will only need one dose of the vaccine this year, while those who were not vaccinated last year will need two doses four weeks apart.
While natural immunity may protect children just as well as a vaccine in some cases, Dr. Roberta DeBiasi, a pediatrician and infectious disease specialist at Children's National Medical Center in Washington, says that's not the case with flu. "The risk of an adverse event if your child gets the flu naturally is markedly higher than if they get the vaccine," DeBiasi says. DeBiasi, a mother of two young kids herself, also is confident that this year's flu vaccine is safe. "This year we have the benefit of having studied the pandemic [H1N1], so we have data for all the flu strains and there's no risk."
--Eliza Barclay
But he still doesn't know why some vaccines work well — and some, not so much.
"There are at least two systems in the immune function," Katz says. "One is called antibody, and the other is called cell-mediated immunity. And with most infections, we'd like to have both of those active."
The human body uses those immune systems to fight off viruses and bacteria. Once those systems are activated, they can remember the bugs and stand ready to fend off new infections for years — or even for a lifetime.
"We think that's what we've achieved with measles," Katz says. "We think that's what we've achieved with polio."
But other vaccines, whether because of the nature of the microbe or the vaccine itself, don't confer lifetime immunity. The vaccine for pertussis, or whooping cough, is one of those.
"We're seeing right now in California, where they're having a large outbreak, that a number of cases are individuals who've received the vaccine," Katz says.
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