The Hows and Whys of Baby Vaccines

Why does every child need to be vaccinated? If most are, isn't my child protected?

In this country, rates of deadly diseases like polio, rubella, diphtheria, and Hib are very low. And other childhood maladies such as rotavirus and chickenpox are declining precisely because children's immunization rates are high. According to the CDC, 77 percent of children under 3 are fully immunized. This creates "community immunity," meaning that a virus won't spread within a community if enough people in the group have developed an immunity to it. So even if someone returns from, say, Italy, Switzerland, or Israel -- where there have been measles outbreaks -- the group is immune. Families that don't vaccinate create chinks in the community immunity where diseases can sneak in. "Diseases like measles and mumps bubble just below the surface," Dr. Offit says. "When immunization rates dip, those viruses come back."

That's exactly what health experts believe is fueling recent spurts of whooping cough as well as the largest measles outbreak this country has experienced in more than a decade. There were 136 measles cases in the first half of 2008. That may not sound particularly high when you consider that, worldwide, measles kills more than 300,000 children every year. But disease experts believe these cases are a troubling sign that immunization rates are falling below the levels necessary to keep measles at bay. Although on average only about 2.5 percent of families opt out of vaccines in states that allow for personal-belief exemptions, some communities have opt-out rates as high as 19 percent. Recent studies show that unvaccinated kids are up to 35 times more likely to contract measles than vaccinated children are. And indeed, nearly half the children caught up in last year's measles outbreak were unvaccinated. "If we could ever get everyone to vaccinate, the disease would be eradicated and we wouldn't have to vaccinate anymore," Dr. Turner says. "But because of exemptors, we're still going to be vaccinating generations down the line."

Parents may believe a decision to opt out and let kids "hide in the herd" affects only their family. But doing so weakens the herd and puts everyone at risk, particularly kids whose vaccines don't "take," babies too young to be vaccinated, and children with cancer and other conditions who can't be immunized and who depend on community immunity for protection. "It's not just protecting your child," Dr. Turner says. "It's protecting everyone's child."

Parents Are Talking

Add a Comment