What’s behind it: Late last year, the parents of 9-year-old Hannah Poling won a lawsuit in which they claimed that their daughter’s autism had been triggered by the five “catch-up” shots for nine diseases she received in one day. She got the injections in 2000, when she was 19 months old. The highly publicized case underscored fears — also raised by actress Jenny McCarthy, who has a son she believes has recovered from autism — that the practice of giving multiple vaccines at once is too much for a small child’s body to handle.

The facts:Hannah Poling was born with a disorder that affects her mitochondria (the structures within cells that produce energy). And though the family won the settlement on the theory that this underlying vulnerability could have made her more susceptible to vaccine injury, there’s actually no proof that she — or any other child with mitochondrial disease — was in fact at any increased risk, says neurologist John Shoffner, M.D., associate professor of biology at Georgia State University, in Atlanta, Georgia, one of the doctors who diagnosed Hannah’s disorder.   “There is no evidence that the contents of vaccines are the cause of autism or mitochondrial disorders,” he says. What’s more, because even common illnesses like colds, the flu, and rotavirus can cause significant harm to these children, doctors strongly advise they receive all the recommended shots.

So what does all of this mean for parents of healthy kids? Not much — getting more than one shot at a time isn’t a huge physical stress. Their immune systems handle far greater challenges from everyday exposure to germs on shared toys, doorknobs, and the playroom floor.  As Dr. Paul Offit explains it: Think about the bugs that caused your child’s last ear infection. Each single bacterium has 2,000 to 3,000 components that stimulate an immune response from the body. As those bacteria multiply, the challenge to the immune system increases exponentially. Your baby feels awful and likely has a high fever and lots of pain. The body pulls out the stops to fight it off. Now compare that to this: “The entire fourteen-shot course of childhood vaccinations contains only about 150 immunological components altogether,” says Dr. Offit. This is about a tenth of the challenge posed by exposure to just one microscopic germ.

What’s more, the bacteria and viruses used in vaccines are either killed or altered, says Martin Myers, M.D., author of “Do Vaccines Cause That?!” There are just enough to induce immunity, but not enough to make someone sick — and certainly not enough to overload the immune system of a healthy child.  In rare instances, some susceptible children experience fever-induced seizures following shots, but though these are frightening, they cause no permanent harm.  These same fever-induced seizures can occur with any viral illnesses.

Splitting Up Vaccines:One common response to these concerns is to break up combination vaccines (which may contain up to five inoculations in one) or to spread them out. But that carries significant risks of its own. “Too often, an immunization delayed is an immunization missed,” says Dr. Schaffner. “It’s hard enough for parents to keep track.”   Coming in to the doctors office to “spread them out” increases your child’s exposure to illness.  Children with mild illnesses ride it out at home.  The sicker children are brought to the doctor’s office to be seen.  While this risk is small, why expose your child to more illness or to the illness you may be trying to prevent, by spreading out the shots.   Finally, there is not even one controlled study that shows spreading out the shots prevents anything. 

More troubling, during the gaps, kids are susceptible to catching serious diseases they could have been protected from. Vaccines are scheduled at certain times for precise reasons: It’s a balance between finding the time when the baby’s immune system can respond and knowing when he’s most in danger of catching the infection, says Dr. Schuchat. Give a shot late and a child is left unprotected at his most vulnerable time.

Why start so early?

The decision as to when to give a vaccine is based on the epidemiology of the vaccine preventable disease. Often, these diseases are more severe in younger children. Therefore, we start early to ensure that the youngest and often most fragile are protected as soon as possible.  For example, most deaths due to pertussis occur in infants younger than 6 months of age.

Please remember that immunizations have been a major public health success story. The vaccine schedule has evolved over the past 50 years based on scientific evidence.   It is your pediatricians job to constantly review this evidence.  Each vaccine must be judged on its individual merit and evidence of benefit.