Misconceptions about Immunization

Misconception #7:
Giving a child more than one vaccine at a time increases the risk
of harmful side effects and can overload the immune system.

Children are exposed to many foreign antigens every day. (An antigen is a substance that stimulates an immune response.) Eating food introduces new bacteria into the body, and numerous bacteria live in the mouth and nose, exposing the immune system to still more antigens. An upper respiratory viral infection exposes a child to 4-10 antigens, and a case of "strep throat" to 25-50. According to Adverse Events Associated with Childhood Vaccines, a 1994 report from the Institute of Medicine, "In the face of these normal events, it seems unlikely that the number of separate antigens contained in childhood vaccines . . . would represent an appreciable added burden on the immune system that would be immunosuppressive." And, indeed, available scientific data show that simultaneous vaccination with multiple vaccines has no adverse effect on the normal childhood immune system.

Studies have been conducted to examine the effects of giving various combinations of vaccines simultaneously. In fact, neither the Advisory Committee on Immunization Practices (ACIP) nor the American Academy of Pediatrics (AAP) would recommend the simultaneous administration of any vaccines until such studies showed the combinations to be both safe and effective. These studies have shown that the recommended vaccines are as effective in combination as they are individually, and that such combinations carry no greater risk for adverse side effects. Consequently, both the ACIP and AAP recommend simultaneous administration of all routine childhood vaccines when appropriate. Research is under way to find ways to combine more antigens in a single vaccine injection (for example, MMR and chickenpox). This will provide all the advantages of the individual vaccines, but will require fewer shots.

Two practical factors favor giving a child several vaccinations during the same visit. First, immunizing children as early as possible provides protection during the vulnerable early months of life. This generally means giving inactivated vaccines beginning at 2 months and live vaccines at 12 months. The various vaccine doses thus tend to fall due at the same time. Second, giving several vaccinations at the same time will mean fewer office visits for vaccinations, which saves parents both time and money and may be less traumatic for the child.


This information is adapted from material that the U.S. Centers for Disease Control and Prevention published in 1996 to help physicians reassure their patients.

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This page was posted on November 11, 1997.

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