Vaccines are given to prevent or reduce the risk of infection from certain diseases. Most vaccines are given through an injection. They contain either a dead or live, but weakened (unable to cause infection) form of the germ. Once inside the body, the immune system recognizes the germ as an invader and mounts an attack to isolate and eliminate it from the body. The immune system retains a "memory" for the germ, so it can quickly and efficiently attack if it's encountered again.

Routine childhood vaccinations protect against measles, mumps, rubella, diphtheria, tetanus, pertussis, polio, varicella (chicken pox), Haemophilus influenzae (Hib), rotavirus, influenza, meningitis, hepatitis A, hepatitis B, pneumonia and, for girls, human papilloma-virus. There are also vaccines for diseases that are not common in this country, but may be recommended to travelers or those living for extended periods in some foreign countries.

There are many benefits to vaccines beyond personal protection from illness, disabling complications or death. Preventing diseases saves the cost of treatment for people who may become sick. In some cases, a disease can be brought under control or eradicated when most of the population is immunized. Immunization reduces the risk of outbreaks since the disease can't easily spread. It also reduces the risk of spreading the infection to those who can't be vaccinated (because of health reasons or religious beliefs).

Booster Needs

Health experts say immunity provided by vaccines may not last and recommend booster doses to maintain protection. Currently, a tetanus booster is given every ten years. Adults may also need a booster for pertussis (whooping cough), measles, mumps and rubella (MMR).

Mark Slifka, Ph.D., Researcher with the Vaccine Gene Therapy Institute at Oregon Health & Science University, says the recommendations for booster vaccinations appear to be made based on judgment, not scientific data. He and his colleagues set out to determine how long immunity lasts for several vaccine-preventable diseases. Using stored blood samples from more than 40 volunteers, the researchers were able to test for immunity (i.e., levels of disease-specific antibodies) over time for smallpox, measles, mumps, rubella, Epstein-Barr and chicken pox.

The researchers found, in most cases, immunity to smallpox, measles, mumps, rubella, Epstein-Barr and chicken pox appears to last a lifetime. On the other hand, protection against tetanus and diphtheria appears to last at least 30 years. Slifka says this finding is important because the current assumption is that vaccine immunity for these two diseases only lasts about ten years.

The research can be backed up by actual practice. Sweden hasn't had any reported cases of tetanus or diphtheria and boosters there are only given every 30 years. Slifka says U.S. health experts may want to re-examine their recommendations for 10-year tetanus/diphtheria immunizations and consider extending the time between adult boosters.

Slifka says while the more frequent vaccinations pose no harm, they add a considerable amount to health care costs. In the future, doctors may be able to test for antibody levels and then give booster doses of vaccines only as they are needed rather than on a pre-determined schedule. Slifka also cautions that children still need to complete their series of immunizations to develop immunity from vaccine-preventable diseases.

For general information vaccines:

Centers for Disease Control and Prevention

Immunization Action Coalition

National Institute of Allergies and Infectious Diseases