How Vaccines Work

By: Alia Hoyt  | 

Vaccine Myths

anti-vaccination protestor
An anti-vaccination protestor demonstrates at a Tea Party rally. Fibonacci Blue/Flckr/CC BY 2.0

Here are some of the most well-known myths about vaccines as well as the reality.

MYTH: Vaccines cause autism.


TRUTH: This myth gained popularity when children were diagnosed with autism around the time that they received the MMR vaccine (around 18 months of age), according to Joyce Allers, RN, with Children's Healthcare of Atlanta. (There was also a now-discredited study published in Lancet in 1998 alleging a connection.) At the time, the mercury-containing preservative Thimerosal was being put in some vaccines – although not the MMR vaccine – to keep bacteria from growing, so many people connected that to autism. However, there appears to be no link between previous use of Thimerosal and autism. Thimerosal was completely removed from all infant vaccines in the United States in 2001, yet autism rates continue to increase. "Study after study has shown that there is no link between vaccines and autism," says Angie Matthiessen with Children's Healthcare of Atlanta.

Thimerosal is currently present only in minute amounts in the influenza vaccine. There are also Thimerosal-free influenza vaccines.

MYTH: Vaccines aren't necessary anymore because all the diseases are gone anyway.

TRUTH: According to the CDC, if we stopped vaccinating, many diseases that are largely unknown would come back with a vengeance. The only vaccine-preventable disease that's been completely wiped out is smallpox. "These diseases are coming into our country, into our schools and into our workplace," says Matthiessen. "Don't believe that your child is 100 percent protected because the disease isn't currently in the United States. International travel and adoption are two of the ways that dangerous diseases make their way into the country."

Measles, which the U.S. considered wiped out in 2000 has returned. There were 1,282 cases of measles in the U.S. in 2019. The CDC attributed the outbreak to "an increase in the number of travelers who get measles abroad and bring it into the U.S., and a spread of measles in U.S. communities with pockets of unvaccinated people." Some Americans have become resistant to immunizing their children, which has contributed to the spread of some childhood diseases that were once seldom seen.

MYTH: Babies are too fragile to get so many shots.

TRUTH: "A lot of young parents are worried about giving their babies so many shots, thinking that they will overwhelm their immune system," says Allers. "I tell them that as human beings we are exposed to disease all the time, like at the mall and church, so we can't overwhelm their systems." According to the Children's Hospital of Philadelphia's Vaccine Education Center, diseases often occur in very young infants, so the best way to prevent them is to give vaccines as soon as possible after birth. "We have a wonderful history of eliminating disease, but what worries us is all the good progress we've made is going to be diminished by families choosing their own vaccination schedule or choosing not to vaccinate at all," Allers says.

MYTH: A live vaccine can give me the disease it's supposed to prevent.

TRUTH: As we've discussed, live vaccines can cause extremely mild symptoms. However, experts agree that they are very minor and much better than coming down with the full-blown disease.

For more information on vaccines and related topics, check out the links below.

Vaccine FAQ

Do vaccines work against mutations?
Vaccines can be tricky to produce because some viruses mutate so quickly that traditional vaccines are ineffective. The COVID-19 vaccine will most likely work against variants in the virus. Scientists released a January 2021 study stating that the Pfizer vaccine shows "no reduction in neutralization activity" for mutations.
How are vaccines made?
The procedure for developing vaccines vary depending on the type of vaccine. But the process usually takes many years and hundreds of millions of dollars.
How do vaccines work?
Vaccines, most often given by hypodermic injection, help the body develop disease-fighting abilities by tricking the body into believing it already has the full-blown disease, triggering an "immune response". The immune system identifies these foreign substances and develops proteins that circulate in the blood that fight the infection. The body then stockpiles these antibodies so they are available to fight off the disease if it's exposed at a later time.
How are vaccines billed?
Generally, if you get a vaccine, it will be directly billed to your insurance provider, though you may be required to cover a co-pay. Some vaccinations are free in the United States, such as the new COVID-19 vaccine. However, most come at a cost, either paid by your insurance company or out of pocket by you. This can get pricey. The cost of a flu shot without insurance ranges from $40 to $70.
How long do vaccines protect you?
The length of protection varies depending on what the vaccination is for. Some vaccines — like chicken pox and measles — protect you for life. Others, like the influenza vaccine, may only protect you for a year or one flu season.

Originally Published: Oct 26, 2007

Related Articles

More Great Links


  • Allers, Joyce, R.N. Personal interview. 22 Aug. 2007.
  • American Academy of Pediatrics.
  • American History.
  • American Veterinary Medical Association.
  • "A Parent's Guide to Vaccine-Preventable Diseases for Children." Toronto, Ontario, CA: Sanofi Pasteur, 2005.
  • Bradley, John, M.D. Personal interview. 30 Aug. 2007.
  • Centers for Disease Control and Prevention. "History of Smallpox." Aug. 30, 2016 (April 24, 2020)
  • Centers for Disease Control and Prevention. "HPV Vaccine Schedule and Dosing." Aug. 15, 2019 (April 24, 2020)
  • Centers for Disease Control and Prevention. "Vaccines by Disease." Nov. 22, 2016 (April 24, 2020)
  • Centers for Disease Control and Prevention. "Whooping Cough is Deadly for Babies." June 29, 2017 (April 24, 2020)
  • Children's Hospital of Philadelphia's Vaccine Education Center.
  • Foster, DVM Race; Marty Smith, DVM and Holly Nash, DVM, MS. "Vaccination Recommendations for Dogs." Pet Education. 4 Sept. 2007.
  • Foster, DVM Race; Marty Smith, DVM and Holly Nash, DVM, MS. "Vaccination Recommendations for Cats and Kittens." Pet Education. 4 Sept. 2007.
  • Many Cases, Real Risks, More Reasons to Protect Yourself. Toronto, Ontario, CA: Sanofi Pasteur, 2006.
  • Immunization Action Coalition.
  • Matthiessen, Angie, MSW. Personal interview. 22 Aug. 2007.
  • Maybury Okonek, Bonnie A. and Pamela M. Peters, Ph.D. "Vaccines: How and Why?" Access Excellence. 25 Aug 2007
  • Malaria Vaccine Initiative.
  • "Measles Deaths Down Worldwide." CNN Online: Health. 19 January 2007. 3 September 2007
  • National Institute of Allergy and Infectious Diseases.
  • Petplace Veterinarians. "Canine Vaccine Recommendations." PetPlace. 4 Sept 07
  • Schaffner, William, M.D. Personal interview. 18 Sept. 2007.
  • "Vaccination Fact vs. Fiction." Philadelphia, PA: Wyeth Pharmaceuticals, Inc., 2005.
  • World Health Organization. "Malaria Vaccines." 2020 (April 24, 2020)