Global Vaccine Safety

Six common misconceptions about immunization

"Giving a child multiple vaccinations for different diseases at the same time increases the risk of harmful side effects and can overload the immune system".

Children are exposed to many foreign antigens every day. 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 four to ten 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 United States, "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 immuno-suppressive."

Indeed, available scientific data show that simultaneous vaccination with multiple vaccines has no adverse effect on the normal childhood immune system.

A number of studies and reviews have been conducted to examine the effects of giving various combinations of vaccines simultaneously. 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.

Research is under way to find ways to combine more antigens in a single vaccine injection (for example, measles, mumps, rubella (MMR) and chickenpox). This will provide all the advantages of the individual vaccines, but will require fewer shots. There are two practical factors in favour of giving a child several vaccinations during the same visit. First, we want to immunize children as early as possible to give them protection during the vulnerable early months of their lives. This generally means giving inactivated vaccines beginning at two 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 clinic visits for vaccinations, which saves parents both time and money and may be less traumatic for the child. In countries where there is a likelihood of reduced contact with the health care system, there is an added advantage of ensuring that there are no missed opportunities to complete the recommended vaccinations for a child.

WHO gratefully acknowledges the permission of CDC Atlanta, to present an edited version of "Six common misconceptions about immunization".