Diseases & Conditions



Children should be vaccinated to protect them against infectious diseases. Vaccines are preparations that contain either noninfectious fragments of bacteria or viruses or whole forms of these organisms that have been weakened so that they do not cause disease. Giving a vaccine (usually by injection) stimulates the body's immune system to defend against that disease. Vaccination is performed to produce a state of immunity to disease and is thus sometimes termed immunization.

Vaccines have eliminated smallpox and have nearly eliminated other infections, such as polio and measles, that were once common childhood scourges in the United States. Despite this success, it is important for health care practitioners to continue to vaccinate children. Many of the diseases prevented by vaccination are still present in the United States and remain common in other parts of the world. These diseases can spread rapidly among unvaccinated children, who, because of the ease of modern travel, can be exposed even if they live in areas where a disease is not common.

No vaccine is 100% effective and 100% safe. A few vaccinated children fail to become immune, and a few develop side effects. Most often, the side effects are minor, such as pain at the injection site, an itchy rash, or a mild fever. Very rarely, there are more serious problems. Vaccines are continuously undergoing improvements to ensure safety and effectiveness. Recent improvements include the use of acellular pertussis (DTaP), which has a much lower chance of causing side effects than the previously used whole-cell pertussis (DPT) vaccine, and the use of an inactivated, injectable polio vaccine (IVP) instead of the previously used oral polio vaccine. The oral polio vaccine, which is made of a live, weakened virus, can cause polio if the weakened virus mutates, which happens once in every 2.4 million children. Although this is an extremely small chance, it led doctors in the United States to completely switch to the injectable polio vaccine. Febrile seizures (seizures that are triggered by a fever) have occurred in about 3 in 10,000 children after receiving the measles-mumps-rubella vaccine. Although the public press has reported concerns that the measles-mumps-rubella vaccine may produce autism, scientific evidence shows that this does not happen.

To help people evaluate the risks of vaccination, the federal government requires doctors to give parents a Vaccine Information Statement each time a child is vaccinated. Also, a federal Vaccine Injury Compensation Program was established to compensate anyone suffering permanent consequences of vaccination. This program was established because doctors and health authorities want as many children as possible to be protected from life-threatening diseases. When considering the risks of vaccination, parents must remember that the benefits of vaccination far outweigh the risks.

Vaccinating Infants and Children

Following the recommended vaccination schedule is important because it helps protect infants and children against infections that can be prevented. The schedule above is based on the one recommended by the Department of Health and Human Services and the Centers for Disease Control and Prevention. The schedule indicates which vaccines are needed, at what age, and how many doses (indicated by the numbers in the symbols).

There is a range of acceptable ages for many vaccines. A child's doctor can provide specific recommendations, which may vary depending on the child's known health conditions and other circumstances. Often, combination vaccines are used, so that children receive fewer injections. If children have not been vaccinated according to the schedule, catch-up vaccinations are recommended, and parents should contact a doctor or health department clinic to find out how to catch up. Parents should report any side effects after vaccinations to their child's doctor.

For more information about this schedule, parents should talk to a doctor or visit the Centers for Disease Control and Prevention's National Immunization Program site.

Most doctors follow the vaccination schedule recommended by the Centers for Disease Control and Prevention, which begins with the hepatitis B vaccine given in the nursery. The recommended ages for vaccinations should not be construed as absolute. For example, 2 months can mean 6 to 10 weeks. Although parents should try to have their children vaccinated according to the schedule, a slight delay does not interfere with the final immunity achieved nor does it entail restarting the series of injections from the beginning. Vaccination need not be delayed, however, if the infant has a slight fever from a mild infection, such as an ordinary cold. Some vaccines are recommended only under special circumstances.

More than one vaccine may be given during a visit to the doctor's office, but several vaccines are often combined into one injection, for example, pertussis, diphtheria, tetanus, and Haemophilus influenzae type b vaccines. A combination vaccine reduces the number of injections needed but does not reduce the safety or effectiveness of the vaccines.

Last full review/revision November 2006 by Ruth A. Lawrence, MD

Source: The Merck Manual Home Edition