Vaccines' Benefits Trump Concerns, Experts Say

Young children receive more than twice the number of inoculations that they did 50 years ago. This worries some parents, but experts say that vaccines have gotten cleaner and more efficient, and are much safer than risking outright illness.

In 1960, health authorities recommended that young children get five vaccines — smallpox, diphtheria, tetanus, whooping cough and polio. In 2009, there are vaccines against 13 diseases for children under the age of 2. That's excluding flu. This increase is worrisome to many parents.

"The extent of concern about immunization is enormous, and it's growing," says Edgar Marcuse, a professor of pediatrics at the University of Washington and coauthor of a paper in the journal Pediatrics that addresses parental concerns.

One of the chief concerns is that babies' immune systems aren't developed enough to handle the onslaught of vaccines. But studies of DPT (a vaccine against diphtheria, pertussis [whooping cough] and tetanus), hepatitis B, Hib (a vaccine against meningitis), and polio vaccines have shown that 90 percent of babies produce an active, protective response to these vaccines.

Marcuse and his colleagues have done some calculations by looking at how many antibodies are needed to respond to an average infection, how many antibodies babies produce after getting vaccinated and how long it takes babies to make enough antibodies to be protective. They predict that if babies received 11 vaccines at the same time, it would use up 0.1 percent of the cells involved in the immune response, which would quickly regenerate.

Today's Vaccines Contain Less Of The Disease

Some parents ask their pediatricians to space out the vaccines. But that's a bad idea, says Marcuse. "When you space out the vaccines, you leave your infant susceptible to diseases you could otherwise have prevented, particularly in the first six to eight months of life," he says. Babies can get diseases such as whooping cough or meningitis, and these can be tough on them.

Babies are going to be exposed to bacteria and viruses in one way or another — either during an outright infection, or in the vaccines, says Saad Omer, a vaccine expert at Emory University.

In the vaccines, he says, babies are only seeing bits and pieces of the viruses or bacteria, and vaccines are much "cleaner" now than they used to be. "A lot of people say that the number of vaccines has gone up," he says. But, in reality, the number of antigens — the molecules in the viruses and bacteria that spark the immune response — hasn't gone up, it's gone down, he says.

The biggest change has been in the pertussis vaccine, which used to contain about 3,000 antigens from the whole pertussis bacterium. Now, vaccinologists have plucked out the five molecules that by themselves can set off an immune response.

Mercury Worries

Some parents worry that thimerosal, a mercury-containing preservative, can hurt the immune system. It's a big issue for parents concerned about vaccines and autism. But mercury is out of virtually all childhood vaccines or present in lower amounts than can be found in a can of tuna.

Omer says parents need to remember that for every type of vaccination, the disease is a bigger challenge to the baby than the vaccine. That's easy to forget today, when few can remember what polio and whooping cough and even measles look like.

"After effective control of these diseases, there's a shift in the mental calculus of parents," Omer says. They stop worrying about the disease, and start worrying about the vaccine. But the measles vaccine causes brain damage in 1 in 1 million recipients. The disease itself, which used to hit the majority of kids, killed 1 in 500 people who got it, and caused brain damage in 1 in 1,000.

Vaccines do have side effects. The immune system sometimes overreacts, and babies can get fevers, soreness and rashes from some vaccines. In those cases, doctors recommend being careful about subsequent vaccinations. But in rare instances — that 1 in 1 million chance with measles vaccines, for example — there can be neurological side effects.

The suggestion from vaccine experts is that babies who already have some sort of infection not get vaccinated until the infection clears up. Otherwise, it's difficult to determine whether the baby is having a side effect from the vaccination, or is suffering from the already existing infection. And the decision about whether babies should get second shots where the first one caused a problem is best made individually, by parents and physicians. Copyright 2010 National Public Radio. To see more, visit http://www.npr.org/.

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