How Do Vaccines Work?
What is a vaccine, and how does it work?
A vaccine causes a response from the body’s immune system to reduce the risk of getting or having serious illness from a specific disease. Vaccines are usually given by injection into a muscle, but some vaccines are given as a nasal spray or are taken by mouth.
Once in the body, the vaccine triggers the immune system to create antibodies. These antibodies counteract or stop the germ that causes the disease. If the body is later exposed to this germ, the immune system will recognize it and produce antibodies to fight it. This immunity may last for about a year or up to your lifetime depending on the specific vaccine.
What are examples of different types of vaccines?
There are several types of vaccines that each work in a different way to produce immunity in the body:
- Inactivated vaccines – contain a killed version of the germ to cause the immune response. You may need several doses over time (booster shots) to get ongoing immunity against diseases.
- Live-attenuated vaccines – contains a weakened form of the germ to cause the immune response. Usually just 1 or 2 doses of most live vaccines can give you a lifetime of protection against a germ and the disease it causes.
- Messenger RNA (mRNA) vaccines – contains a manufactured mRNA that signals the body to make proteins that cause an immune response in response to the germ. mRNA vaccines have a benefit of a shorter manufacturing time.
- Subunit, recombinant, polysaccharide, and conjugate vaccines – use specific pieces of the germ to cause an immune response that’s targeted to key parts of the germ. You may need booster shots to get ongoing protection against diseases.
- Viral vector vaccines – place material from the germ on a modified version of another harmless virus to deliver into the body and cause an immune response.
What else may be in a vaccine product?
You may be heard that vaccines may contain other ingredients. These ingredients may have a specific function to maintain effectiveness, safety, and stability during storage and administration. These ingredients usually fall into one of these categories:
- Stabilizers – to maintain effectiveness after manufacturing.
- Adjuvants – to help boost the immune response to the germ.
- Residual ingredients – trace amount left over from the manufacturing process. For example, some vaccines contain egg protein which may be an issue for people that are allergic to eggs.
- Preservatives – are included to prevent contamination of the vaccine with outside germs.
Do vaccines always prevent disease?
Usually, but not always. Because immunity can take weeks to develop after vaccination, it is possible to become infected shortly following vaccination. In some cases, vaccinated people can and sometimes do get infected. But a vaccinated person is far less likely to die or become seriously ill than someone whose immune system has not been prepared to fight an infection.
Influenza vaccines are specifically formulated each year to target predicted strains of the influenza virus. If the prediction does not match the strain in the community, then there is the possibility of having some flu symptoms, but you are likely to avoid serious illness.
Can diseases be eliminated by getting vaccinated?
When high vaccination rates occur in the population, the presence of a bacteria or virus may be decreased in the community which lessens the chance of being infected. This even may help someone who has not been immunized against the disease. This "herd immunity" is important because some persons cannot be vaccinated or do not achieve full immunity such as those with cancer or taking immunosuppressants. Over time some diseases, such as smallpox, may be eliminated.
Summary
Vaccines are a safe and effective treatment to prevent many serious illnesses. Be sure to follow your doctor’s recommendations for vaccination and check with them periodically to make sure that you are up to date.