Vaccination protects children against many infectious diseases. Vaccines contain either noninfectious components 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 also called immunization because it produces a state of immunity to disease (see also Overview of Immunization).
For additional information about specific vaccines, see the following:
Childhood Vaccination Schedules
In the United States, childhood vaccination follows a schedule recommended by the Centers for Disease Control and Prevention (CDC), which begins with the hepatitis B vaccine given soon after birth and continues throughout childhood:
Recommended Immunizations for Birth Through 6 Years Old, United States, 2025
Recommended Immunizations for Children 7 to 18 Years Old, United States, 2025
Parents should try to have their children vaccinated according to the recommended schedule. A significant delay in vaccination puts children at risk of the serious diseases the vaccines could prevent. If children miss a vaccine dose, parents should talk to their doctor about catching up with the schedule. Missing a dose does not require children to restart the series of injections from the beginning. The following schedule is used to catch up when children have not received vaccinations according to the usual schedule:
Vaccination does not need to be delayed if children have a slight fever resulting from a mild infection, such as an ordinary cold.
Some vaccines are recommended only under special circumstances—for example, only when children have an increased risk of getting the disease the vaccine prevents.
More than one vaccine may be given during a visit to the doctor's office, and several vaccines may be given at the same visit. For example, there is a combination vaccine that contains pertussis, diphtheria, tetanus, polio, and Haemophilus influenzae type b vaccines. A combination vaccine simply reduces the number of injections needed and does not reduce the safety or effectiveness of the vaccines. (See also CDC: Multiple Vaccines at Once.)
Vaccine Effectiveness
Vaccination is effective in preventing serious disease. Without vaccines, diseases such as measles and whooping cough can make children seriously ill or may even be fatal. Vaccines have been so effective that many health care professionals currently in practice have seen few or no cases of diseases that were once extremely common. However, because of the rise in numbers of unvaccinated children, these diseases are once again coming to the forefront.
Vaccines have eliminated smallpox and have nearly eliminated other infections, such as polio, that were once common causes of chronic health issues or death in children. However, many of the diseases prevented by vaccination are still present in the United States and remain common in some parts of the world. These infections 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. Therefore, it is important for children to continue to be vaccinated.
Vaccine Safety
Vaccines that are approved for clinical use are generally safe and effective. No vaccine (or other medication) is 100% effective and 100% safe. A few vaccinated children do not become immune, and a few develop side effects. Most often, the side effects are minor, such as pain and redness at the injection site, a rash, or a mild fever. Very rarely, there are more serious problems.
Vaccine Adverse Event Reporting System (VAERS)
Before a new vaccine can be licensed, it, like any medical product, is tested in clinical trials. Such trials compare the new vaccine to a placebo or to a previously existing vaccine for the same disease to assess whether the vaccine is effective and to identify common side effects. However, some side effects are too rare to be detected in any reasonably sized clinical trial and do not become apparent until after a vaccine is used routinely in many people. Thus, a surveillance system called the Vaccine Adverse Event Reporting System (see VAERS) was created to monitor the safety of vaccines that are used in the general public.
VAERS is a safety program cosponsored by the U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC). It is used to collect reports from people who believe that they had a side effect after a recent vaccination and from health care professionals who identify certain possible side effects after a vaccine was given, even if they are unsure the effects are related to the vaccine. Thus, the existence of a VAERS report is not proof that a vaccine caused a certain side effect. VAERS is simply a system for collecting data about things that might be side effects. Then, the FDA can further evaluate the concern by comparing how often the possible side effect occurred in people who were vaccinated to how often it occurred in people who were not vaccinated. To help people evaluate the risks and benefits of vaccination, the United States government requires doctors to give parents a current vaccine information statement (VIS) each time a child is vaccinated.
When considering the risks and benefits of vaccination, parents must remember that for most children the benefits of vaccination far outweigh the risks.
Effects of Vaccine Hesitancy on Public Health
Vaccine hesitancy is when parents delay or do not consent to their children being given some or all of the recommended vaccines despite the availability of vaccine services. Delaying or not consenting to vaccines affects public health. When fewer people are vaccinated, the percentage of a population that is immune to disease, also called herd immunity, decreases. Then, diseases become more common, particularly among people who are at increased risk of getting diseases.
People may be at increased risk because
They were vaccinated but did not become immune.
They were vaccinated, but their immunity has decreased over time, which may occur as people age.
Their immune system is impaired by a disorder or a medication (such as the medications used to treat cancer or prevent rejection of a transplant) and they cannot be given live-virus vaccines, such as the MMR or varicella vaccine.
More Information
The following English-language resources may be useful. Please note that The Manual is not responsible for the content of these resources.
