The vaccines young children get in well-child visits protect them against major diseases such as measles, mumps, german measles, whooping cough and hepatitis. Immunizations are important for both individual and public health because they stop the risk of widespread outbreaks of preventable diseases among children and adults.

The number of immunizations children receive has increased as more vaccines have been developed over the years. In 1994, there were eight routine immunizations; in 2010 there were 14. These now protect children against 14 different diseases, the complications of which range from mild illness — such as hearing loss and sterility — to chronically disabling conditions and death.

Many parents are concerned about the number of vaccines their children receive. Some worry that the heavy vaccination load stresses the immune system in a way that leads their children to be more vulnerable to diseases that are not preventable with vaccines. These parents may be less likely to follow recommended vaccine schedules and may even stop immunizing their children.

Being exposed to vaccine antigens does not appear to increase a child's vulnerability to other diseases.

While presumably well-intentioned, this strategy puts their children at risk for severe infections that could be avoided. A new study makes clear that vaccinating a child does make them more vulnerable to other diseases.

To investigate whether the current schedule of recommended vaccines led children who were immunized to “catch” more illnesses not targeted by the vaccines, researchers randomly-selected the emergency records of 193 children diagnosed with illnesses that might be linked to vulnerabilities brought on by vaccines. They compared each child in this group with four control children (total control group 751) who were similar in age, health and demographics, but who had not been diagnosed with the targeted illnesses. The study population was selected from about 500,000 infants over the 12-year period of the investigation and included kids who ranged in age from birth to 47 months.

The researchers compared the immunization records of all the children to determine whether they had similar numbers of shots, and similar exposure to vaccine components that could stimulate the immune system. Specifically, they focused on exposure to vaccine antigens, which are proteins or other compounds that induce an immune response in the body. They looked at the cumulative antigen exposure that occurred through immunizations obtained during the first 23 months of the children's lives.

The findings should reassure parents and health care providers. Being exposed to vaccine antigens does not appear to increase a child's vulnerability to other diseases. Children who were admitted to the hospital with an infectious disease not targeted by vaccines had antigen levels similar to those of children without such visits, suggesting that vaccination did not raise the risk of infection.

Now parents can add more evidence that supports the safety and health benefits of the current immunization recommendations. Parents who remain concerned should discuss their fears with their child's pediatrician. The study is published in JAMA.