Vaccine Safety and Effectiveness

Vaccines are included among the Ten Great Public Health Achievements in the period between 1900 and 1999 because they have a long history of successfully protecting people and communities against infectious diseases by reducing the spread of disease and preventing hospitalizations and deaths. Because of vaccines, serious diseases like smallpox have been eliminated and diseases such as polio and diphtheria are now rare in the United States. Most physicians in the U.S. rarely — if ever — treat a case of measles.

While no vaccine offers 100% protection, they are extremely effective and are our best defense against infectious diseases.  Even if the vaccine does not prevent infection in every person, they often reduce the risk of serious disease and death from the disease. The number of people who experience devastating effects from vaccine-preventable infectious diseases is at an all-time low. To continue that success, we must make sure vaccines are safe and readily available.

Vaccines are constantly under study to ensure they are safe and effective. They undergo rigorous studies designed to measure safety as well as how well they work and potential side effects. In addition, once a vaccine is released, the safety of the vaccine continues to be monitored.  Vaccines — like all medications and procedures — have potential risks that must be weighed against the benefits. The risks for serious complications are quite low and are typically comparable to those associated with common prescription medications.  At DHEC, we always recommend that you ask your health care provider about what vaccines are best for you and your family.

While there can be side effects from vaccines, severe adverse events are far rarer than complications from vaccine-preventable diseases. Most people do not have serious side effects from vaccines; common side effects include muscle aches or mild fever. Such side effects are often signs the body is building a healthy immune response to protect us from disease.

Certain vaccines are updated periodically to keep up with changes in the germs they protect against. The flu vaccine is updated from season to season to protect against the virus strains that research suggests will be common during the upcoming flu season. The COVID-19 vaccine has been updated to best combat new virus variants, or strains, and would be updated as needed in the future. 

The U.S. Food and Drug Administration’s (FDA) Center for Biologics Evaluation and Research regulates vaccine use in the United States and works to ensure safety of vaccines at every stage. Before vaccines are approved, the FDA requires that expert researchers show they are effective and safe. The CDC Advisory Committee on Immunization Practices recommends vaccines for certain groups of people once they establish that benefits of a vaccine in preventing disease outweighs potential risks.

Visit the links below for more information on vaccines: