WASHINGTON, Feb. 20 —  U.S. parents worried about the 20 or so shots their babies must undergo before age 2 were given a bit of reassurance on Wednesday with a report from the Institute of Medicine concluding the immunizations do not damage the infant immune system.

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       THE REPORT from the IOM, an independent group of specialists who advise the government, found no link between the vaccinations and type 1 diabetes, pneumonia, meningitis or other infections.
       Their report adds to a series of studies clearing vaccines of causing dangerous side-effects in children. Last year the committee found no link between the combined measles, mumps and rubella (MMR) vaccine and autism.
       However, there is not enough evidence yet to decide if multiple shots increase the risk of developing asthma, the panel of independent scientists concluded. But panel chairwoman Dr. Marie McCormick of the Harvard School of Public Health believes it is unlikely there is an association.
       The report should reassure parents that “there’s not a lot of support for those risks” critics often cite, McCormick said.
       “Some parents think that with the increased numbers of vaccinations being given to children under the age of 2 ... somehow the infant immune system isn’t up to it and is overwhelmed,” she said.
       
Are your child's shots up-to-date?

       
MANY PARENTS MISTRUSTFUL
       Recent surveys suggest about 25 percent of parents worry that infants get so many vaccines that the shots could overwhelm their immature immune systems and cause infections or immune-related disorders.
       People are also mistrustful because several vaccines were recently pulled off the market, including those that contained the mercury-based preservative thimerosol and a rotavirus vaccine that protects against diarrhea but which was linked with intestinal problems.
       In 1980, babies were immunized against four diseases. Today, by age 2 most children have had up to 20 shots to protect against 11 diseases.
       But babies actually are exposed to fewer antigens — foreign substances that trigger an immune response — now than in previous decades, the institute said. For example, pertussis vaccine given in the 1980s contained about 3,000 potential antigens, while a safer version introduced in the ’90s has about five. Today’s hepatitis B vaccine has only one antigen; smallpox shots given until 1971 had 200.
       
WITHSTANDING MULTIPLE JABS
       And studies show that babies withstand the jabs very well. In fact, research suggests the capacity of the infant immune system is at least 1,000 times greater than what is required to respond to immunization.
       “It is a competent immune system,” McCormick said. “Babies have to be able to deal with bugs.”
       Dr. Paul Offit, a pediatrician and chief of infectious disease at Children’s Hospital in Philadelphia, said a baby’s immune system has a lot more to deal with than vaccines.
       “When you are in the womb, you are in a sterile environment,” he said in a telephone interview.
       “By the end of your first week of life you have been colonized with tens of thousands to hundreds of thousands of whole bacteria.” The baby’s immune system is responding to each of these.
       Also, numerous studies show multiple shots do not increase the incidence of type 1 diabetes or such infections as colds, ear infections, pneumonia or meningitis, the panel concluded.
       However, some studies suggest certain vaccines might increase the risk of allergic disorders such as asthma, while others find no link. So the panel concluded there is insufficient evidence to decide if asthma could be linked to multiple shots.
       Still, many other factors play a role in who gets asthma, so the conflicting studies suggest that even if the shot risk is real, it’s not large, McCormick said. Thus, “on balance, we would recommend immunization.”
       But parents need more clear, scientific information about vaccine risks and benefits, the panel said, urging the government to form a task force to ensure that happens.
       There already is such a group, but health officials will consider whether it needs improvement, said Health and Human Services spokesman Bill Hall.
       McCormick added that parents living in the early 21st century have to remember how awful some of these diseases are.
       “These are not nice diseases. These are bad diseases,” she said. Diphtheria, whooping cough and tetanus can kill, as can measles. Meningitis is deadly and crippling.
       Measles can cause encephalitis and a long-term condition that causes children to become demented in adolescence, known as subacute sclerosing panencephalitis. Even chickenpox can have deadly side-effects.
       
       The Associated Press and Reuters contributed to this report.
       

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