Vaccines have contributed to a significant reduction in many childhood infectious diseases, such as diphtheria, measles, and Haemophilus influenzae type b (Hib). Some infectious diseases, such as polio and smallpox, have been eliminated in the United States due to effective vaccines. It is now rare for children in the United States to experience the devastating and often deadly effects of these diseases that were once common in the United States and other countries with high vaccination coverage.
The vast majority of vaccines are given to healthy babies, children and adults; therefore, it is critical that vaccines be demonstrated to be safe and effective. Ensuring the safety and effectiveness of vaccines is one of the Food and Drug Administration’s (FDA) top priorities. The Center for Biologics Evaluation and Research (CBER) is the center within FDA that has regulatory oversight of vaccines in the United States assuring the availability of safe and effective vaccines.
Because immunization programs of the 20th century were so successful, many of today’s parents have never seen many vaccine-preventable diseases and do not understand the potential for them to re-emerge. If too many individuals choose not to vaccinate themselves or their children, some diseases that are now rare or non-existent in this country may resurface.
The viruses and bacteria that cause vaccine-preventable diseases and death still exist and can cause disease in people who are not protected by vaccines. For example, although measles has not been constantly present in the United States since 2000, sporadic cases continue to occur, primarily from unvaccinated visitors who are bringing the disease into the United States from other countries or unvaccinated U.S. travelers returning to the U.S. from countries where measles is still common, including countries in Europe, Asia, the Pacific, and Africa. The United States began experiencing a large multi-state measles outbreak in December 2014 that started in California and spread to additional states and Mexico. The majority of people who got measles were unvaccinated. The initial patients who were confirmed with measles reported visiting two Disneyland Resort Theme Parks in Orange County, California, from December 17 through December 20, 2014. The source of the outbreak is unknown, but it is likely that a traveler (or more than one traveler) who became infected with measles overseas visited one or both of the Disney parks in December during the time that they were infectious.
Measles is one of the most contagious diseases and can cause severe complications, including pneumonia, swelling of the brain, and death. Outbreaks of infectious diseases, such as measles, serve as a reminder that they are only a plane-ride away and the best way not to get sick is to get vaccinated.
Benefits and Risks
A vaccine is a medication. Like any medicine, vaccines have benefits and risks, and although highly effective, no vaccine is 100 percent effective in preventing disease or 100 percent safe in all individuals. Most side effects of vaccines are usually minor and short-lived. For example, a person may feel soreness at the injection site or experience a mild fever. Serious vaccine reactions are extremely rare, but they can happen.
“Parents should know that the risk of being harmed by a vaccine is significantly smaller than the risk of serious illness from infectious diseases,” says Marion Gruber, Ph.D., director of the Office of Vaccines Research and Review in CBER. “Vaccination is a very important step to get children off to a healthy start.”
For more information on potential adverse events or reactions, talk with your healthcare provider, and many vaccines also have FDA-approved labeling for the patient that can be a resource of information. It is important to discuss with your healthcare provider any prior reactions to vaccines and any adverse reactions following vaccination.
How vaccines work
Vaccines work by preparing the body’s immune system for future attacks by a certain disease, caused by either viruses or bacteria. Vaccines contain weakened bacteria or viruses, or parts of bacteria or viruses, and mimic these disease-causing agents (which are called antigens). As a result of vaccination, the body’s immune system thinks the antigens from the vaccine are foreign and shouldn’t be in the body, but the antigens don’t cause disease in the person receiving the vaccine. After receiving the vaccine, if the virus or bacteria that cause the real disease then enters the body in the future, the immune system is prepared and responds quickly and forcefully to attack the disease-causing agent to prevent the person from getting sick. Vaccines are frequently given by injection (a shot), but some are given by mouth and one is sprayed into the nose.
There are various types of vaccines that are routinely given to children
- Attenuated (weakened) live viruses– These vaccines contain a live virus that has been weakened during the manufacturing process so that they do not cause the actual disease in the person being vaccinated. However, because they contain a small amount of the weakened live virus, people with weakened immune systems should talk to their healthcare provider before receiving them. Examples include vaccines that prevent chickenpox and rotavirus and measles, mumps and rubella.
- Inactivated (killed) viruses– These vaccines contain a virus that has been killed so as not to cause disease, but the body still recognizes it and stimulates production of antibodies against the disease. They can be given to individuals with weakened immune systems. Examples include vaccines to prevent polio and hepatitis A.
- Subunits– In some cases, the entire virus or bacteria is not required for an immune response to prevent disease; just the important parts, a portion or a “subunit” of the disease-causing bacteria or virus is needed to provide protection. The vaccine to prevent influenza (the flu) that is given as a shot is an example of a subunit vaccine, because it is made with parts of the influenza virus.
- Toxoids– Some bacteria cause illness in people by secreting a poison (a toxin). Scientists discovered that weakening the toxins, so that they are “detoxified” does not cause illness. Examples of vaccines that contain toxoids include those to prevent tetanus and diphtheria disease.
- Recombinant– These vaccines are made by genetic engineering, the process and method of manipulating the genetic material of an organism. An example of this type of vaccine is those that prevent certain diseases caused by the human papillomavirus (HPV), such as cervical cancer. In this case, the genes that code for a specific protein from each of the virus types of HPV included in the vaccine are expressed in yeast to create large quantities of the protein. The protein that is produced is purified and then used to make the vaccine. Because the vaccine only contains a protein, and not the entire virus, the vaccine cannot cause the HPV infection. It is the body’s immune response to the recombinant protein(s) that then protects against infection by the naturally occurring virus.
- Polysaccharides– To protect against certain disease-causing bacteria, the main antigens in vaccine are sugar-like substances called polysaccharides; these are purified from the bacteria to make polysaccharide vaccines. However, vaccines composed solely of purified polysaccharides are only effective in older children and adults. Pneumovax 23, a vaccine for the prevention of pneumococcal disease caused by 23 different strains, is an example of a polysaccharide vaccine.
- Conjugates– Vaccines made only with polysaccharides do not work very well in young children because their immune system has not fully developed. To make vaccines that protect young children against diseases caused by certain bacteria, the polysaccharides are connected to a protein so that the immune system can recognize and respond to the polysaccharide. The protein acts as a “carrier” for the part of the vaccine that will make protective antibodies in the body. Examples of conjugate vaccines include those to prevent invasive disease caused by Haemophilus influenzae type b (Hib).
Review the vaccine information sheets
These sheets explain both the benefits and risks of a vaccine. Healthcare providers are required by law to provide them.
Talk to your healthcare provider about the benefits and risks of vaccines
Learn the facts about the benefits and risks of vaccines, along with the potential consequences of not vaccinating against diseases. Some parents and caregivers are surprised to learn that children can be harmed or die of measles, diphtheria, pertussis, and other vaccine-preventable diseases.
Conditions to make your healthcare provider aware of before vaccination
This might include being sick or having a history of certain allergic or other adverse reactions to previous vaccinations or their components. For example, eggs are used to grow many influenza (flu) vaccines; therefore, it is important to inform the healthcare provider if a child is severely allergic to eggs.
The packaging of some vaccines that are supplied in vials or prefilled syringes may contain natural rubber latex, which may cause allergic reactions in latex-sensitive individuals; therefore, an allergy to latex is helpful to inform healthcare providers of beforehand.
It is also particularly important to discuss with your healthcare provider which vaccines should or should not be given to children who have weakened immune systems.
Report adverse reactions
Adverse reactions and other problems related to vaccines should be reported to the Vaccine Adverse Event Reporting System, which is maintained by FDA and the Centers for Disease Control and Prevention (CDC). For a copy of the vaccine reporting form, call 1-800-822-7967, or report online to http://www.vaers.hhs.gov