Combination Vaccines

Dr. Parang Mehta, MD.

Vaccines are becoming available against more and more diseases. While it is a relief that many major illnesses can be avoided, children these days have to take a large number of vaccines, most of them by injection. Often, multiple injections are given to a baby at a hospital/clinic visit. Combination vaccines were developed to reduce the number of "shots" a child has to endure.

Combining vaccines is not a new idea. Influenza vaccine, which is a combination of three or four different vaccines, has been in use for almost seventy years. The DTP vaccine combines diphtheria, tetanus, and pertussis vaccines, and six component pneumococcal vaccine was in use in the 1940s. Three component poliomyelitis vaccines, and the MMR (measles, mumps, and rubella) vaccines have also been in use for half a century. There is a lot of experience with using vaccine combinations in children.

Most combination vaccines available today are for the common childhood illnesses. They are usually combinations of DTP with hepatitis B, hemophilus influenzae b, and injectable poliomyelitis vaccines in various permutations and strengths. Such combinations allow a child to receive protection against up to six diseases with a single shot.

Do combinations work?

Making a combined vaccine is not as simple as mixing two existing vaccines. There are many problems the vaccines may have with each other - physical, chemical, and biological (the last, only with live vaccines like measles and chicken pox). The vaccines to be combined not only have to be physically and chemically compatible, but they must generate adequate immunity against the different diseases when used together. There are many reasons for failure, as can be seen. Many candidate combination vaccines are never put on the market, and some are withdrawn after introduction.

For a vaccine to be licensed for use in humans, the manufacturer must prove that the combination provides the same protection, or nearly so, as each of the component vaccines used separately. There must also be stringent studies about the safety of the combination product. Without such evidence, a combination cannot be marketed. Thus, any combination vaccines being marketed are of proven efficacy and safety.

Immune Overload - does it happen?

This is a popular but baseless concept. It is said that so many antigens at one time will overload the immune system of a baby, and reduce the vaccination efficacy. It may also lead to other disorders of immunity.

Babies are exposed to thousands of antigens in the environment every day, and easily mount an immune repsonse where needed. Six, eight, or ten antigens in a combinatin vaccine are not likely to strain the immune system of a normal baby. Small pox vaccine (when it was used) and the whole cell whooping cough (pertussis) vaccine, contain dozens of antigens each. The immune system getting overwhelmed was never reported. Children tolerated the old vaccines easily and effectively, and the new ones are also not a problem for the immune system of a baby.

Last Revision: July 2, 2020