How do Immunizations Work?

The immune system functions to protect the body against illness and infection. When an organism (bacterium or virus) is foreign to the body, the immune system detects the organism and responds by creating proteins called antibodies. Antibodies fight the infection and help the person to recover. Antibodies also work to prevent a person from becoming ill in the future. If a person is exposed to the organism again, the immune system recognizes it and rapidly produces more of the antibodies required to destroy the organism. This response protects the individual from developing the disease, ideally for life. For example, a person who had chickenpox as a child is unlikely to develop it again, even if he or she is in close contact with a person who is infected. 

Vaccines work by stimulating the immune system to produce antibodies. However, unlike bacteria and viruses, vaccines do not cause the person to become ill in order to develop these antibodies.

 Are there any side effects of vaccines?

The important thing to remember is that immunizations protect children and adults from serious, often life-threatening infection. However, many parents are concerned about the risks of vaccination. Most vaccines are safe and cause few, if any serious side effects. Very rarely, serious side effects do occur. Children who develop unusual reactions such as rashes involving much of the body surface, difficulty breathing, excessively high fevers, seizures or loss of consciousness within a short time after receiving a vaccine should be evaluated by a healthcare provider. To report an unusual reaction after a vaccine, anyone can contact the national Vaccine Adverse Events Reporting System (VAERS, www.vaers.org 1-800-822-7967). Parents who are concerned about a particular vaccine should discuss their concerns with their child's healthcare provider.

What are some of the typical concerns about vaccinations?

There have been concerns within the general public about the safety of vaccination for children. These concerns include use of the preservative thimerosal and the relationship between vaccines and autism. Despite this concern, there is no scientific evidence that receiving vaccines causes or increases the risk of developing autism. Studies that raised this possibility had significant weaknesses in their design. Several of the studies were based on a small number of children and relied upon the memory of parents or pediatricians to recall when behavioral signs/symptoms related to autism began. Most studies did not include a control group to compare children who were vaccinated with those who were not vaccinated to determine if there was a cause and effect relationship. For more information about any potential link between vaccines and autism, visit the National Immunization Program Web site at  www.cdc.gov/od/science/iso/concerns/mmr_autism.htm .

 What should parents do?

Parents of young children may no longer appreciate the potential severity or dire consequences of the illnesses. Parents who lack such appreciation may be willing to forego immunizations for their children, particularly when unproven risks (i.e. autism) are highly publicized. When this occurs, immunization rates decline and outbreaks of infectious diseases, such as measles and pertussis, may occur with significant impact.  

Immunizations are one of the most effective ways to prevent serious illness in children and adults. Pediatric immunization programs in the United States have been quite successful in reducing the number of children affected by a range of highly contagious diseases, including measles, rubella, mumps, diphtheria, and poliomyelitis.  

There is a lack of evidence for an association between vaccines and chronic disease, including autism. Withholding vaccines from a child because of a hypothetical risk places the child at risk for actual infection that may have actual damage on the child’s health.

HCPH encourages parents to talk with a trusted health care provider about their vaccine questions and concerns. Reliable vaccine information is just a click away at www.cdc.gov or www.aap.org.  

* Dales, L., et al. Time trends in autism and in MMR immunization coverage in California. JAMA 285:1183-1185, 2001 http://jama.ama-assn.org/cgi/content/full/285/9/1183]