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 Overview of Immunization Immunization (vaccination) helps the body defend itself against diseases caused by certain bacteria or viruses. Immunity (the ability of the body to defend itself against diseases caused by... read more ).
Vaccine Effectiveness
Vaccines have eliminated smallpox Smallpox Smallpox is a highly contagious, very deadly disease caused by the variola virus. The disease is now considered eliminated. There have been no cases of smallpox since 1977. People can acquire... read more 
and have nearly eliminated other infections, such as polio Polio Polio is a highly contagious, sometimes fatal enterovirus infection that affects nerves and can cause permanent muscle weakness, paralysis, and other symptoms. Polio is caused by a virus and... read more , that were once common causes of chronic health issues or death in children. 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 some parts of the world. For example, in 2019, there were 1,249 cases of measles, mostly in unvaccinated people. This is the greatest number of measles cases in the United States since 1992. 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.
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.
Vaccines are continuously undergoing improvements to ensure safety and effectiveness. Improvements include the use of
Acellular pertussis vaccine (typically combined with diphtheria and tetanus vaccine— DTaP Diphtheria-Tetanus-Pertussis Vaccine The diphtheria, tetanus, and pertussis vaccine is a combination vaccine that protects against these three diseases: Diphtheria usually causes inflammation of the throat and mucous membranes... read more ), which has a lower chance of causing side effects than the previously used whole-cell pertussis vaccine (also combined with diphtheria, and tetanus—DPT)
An inactivated, injectable polio vaccine Polio Vaccine The polio vaccine protects against polio, a very contagious viral infection that affects the spinal cord and brain. Polio can cause permanent muscle weakness, paralysis, and sometimes death... read more (IPV) instead of the previously used oral polio vaccine (OPV)
OPV, which is made of a live, weakened virus, can cause polio if the weakened virus mutates. This is rare and happens once in every 2.4 million children. In the United States, IPV is used, but some countries use OPV because the risk is extremely low and the oral vaccine is less expensive and easier to administer.
Vaccine Adverse Event Reporting System (VAERS)
Before a new vaccine can be licensed, it, like any medical product, is tested in controlled clinical trials How Doctors Try to Learn What Works Doctors have been treating people for many thousands of years. The earliest written description of medical treatment is from ancient Egypt and is over 3,500 years old. Even before that, healers... read more . 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 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 (or other medication) 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 practitioners 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.
National Vaccine Injury Compensation Program
To help people evaluate the risks and benefits of vaccination, the U.S. government requires doctors to give parents a Vaccine Information Statement each time a child is vaccinated. Also, the National Vaccine Injury Compensation Program has been established to compensate people with proven vaccine-related injuries. 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 and benefits of vaccination, parents must remember that for most children the benefits of vaccination far outweigh the risks.
More Information
The following are some English-language resources that may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
Vaccine Adverse Event Reporting System (VAERS): Where and how to report side effects of vaccines
National Vaccine Injury Compensation Program: Where and how to claim a vaccine injury benefit
Vaccine Safety: A resource providing information regarding all aspects of vaccine safety, including safety monitoring and research
