Vaccines help develop immunity by imitating an infection. This type of infection doesn’t cause illness, but it does cause the immune system to produce antibodies that help protect you from the disease in the future. Vaccines contain ingredients called antigens, which tell the body’s immune system to create those antibodies.

Every day, a healthy child’s immune system successfully fights off millions of antigens—the parts of germs that cause the body’s immune system to go to work.

The antigens in vaccines come from the germs themselves, but the germs are weakened or killed so they cannot cause serious illness. Vaccines contain only a tiny fraction of the antigens that children encounter every day in their environment, even if they receive several vaccines on one day.

  • Kids are exposed to 2,000 to 6,000 antigens every day.
  • A strep throat infection, for example, exposes children to at least 25 to 50 antigens. That’s comparable to the antigens in the vaccines that infants get at their two-month visit–the DTaP, IPV, HepB, Hib, and rotavirus vaccines combine to just 54 antigens.

And even though children receive more vaccines to protect against more diseases now compared to 20 years ago, the actual number of antigens in vaccines is dramatically less than decades ago because vaccine technology has improved, making vaccines more efficient.

  • With the 1980 immunization schedule, vaccines contained more than 15,096 antigens.
  • Today’s vaccines contain only 177 antigens in 12 vaccines that protect children and teens against 16 vaccine-preventable diseases.

Antigen Infographic
Source: Verywell: Antigen Counts in Vaccines

Vaccines also contain very small amounts of other ingredients—all of which play necessary roles either in making the vaccine, or in ensuring that the final product is safe and effective.

While some of the names of certain ingredients may sound strange or even alarming, the ingredients are necessary and safe. Talk to your child’s doctor about any questions you have about vaccine ingredients.

See our answer on vaccine ingredient safety here.

Sources:
CDC: Making the Vaccine Decision
Children’s Hospital of Philadelphia: Vaccine Ingredients
Verywell: Antigen Counts in Vaccines