How Do Vaccines Work?

Published: March 09, 2021
Samantha Lewiston
By Samantha Lewiston, PharmD
Barbara Young
By Barbara Young, PharmD

Vaccines are recommended by health care professionals to prevent disease and are an important part of keeping communities healthy. Vaccines prepare our bodies to fight off serious diseases effectively. Without this preparation, vaccine-preventable diseases may cause serious illness, complications, and may spread to others.

What is a vaccine, and how does it work?
A vaccine is a biologic product that protects the body from a specific disease by causing a response from the body’s immune system. Vaccination, or giving a vaccine, often involves an 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. The immune system makes these antibodies to 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.

How long do vaccines last? What is a booster shot?
Vaccines provide protection for a long time, sometimes life-long. However, each vaccine is different, and some are recommended for you to receive more frequently (the influenza vaccine, for example) to provide ongoing protection.

For some vaccines, the protection against germs may slowly decrease over time, and therefore, another shot (booster shot) may need to be given. This additional dose “boosts” the immune system to create antibodies to the disease and extends the protection.

Other diseases, such as influenza, may have different types of germs over time so they require a change in vaccines to provide optimal protection.

Why are vaccines given to babies and children?
Babies have some immunity at birth from their mother for a few weeks and also may be helped by breastfeeding in the early weeks. As their immune systems develop, they need vaccines to develop protection against serious diseases beginning at around two months of age. Without this protection, babies may get seriously ill.

As a child grows, additional vaccines are needed based on how your child’s immune system responds to vaccines at various ages and how likely your child is to be exposed to a particular disease. It is important for your child to receive these vaccines on schedule and as advised by their doctor. Please see the CDC’s Immunization Schedule for children (birth to 18 years) for more information.

Why are vaccines given to adults, and especially older adults?
Adults also need to keep their vaccinations up to date because immunity from childhood vaccines can wear off over time. Older adults need protection against diseases that are more common as people age, such as shingles or pneumonia.

Adults may need other vaccines based on age, health conditions, job, lifestyle, or travel habits. Talk to your doctor about what other vaccines may be recommended for you and when you should receive them. For more detailed information, please see the CDC’s Immunization Schedule for ages 19 and older.

Vaccines protect the body from a specific disease by causing a response from the immune system. While vaccines provide long-lasting protection, multiple doses or booster doses may be required for the best protection. Vaccines are important for decreasing illness and complications from vaccine-preventable diseases. Vaccines also prevent diseases from being spread to others in the community. Vaccines are particularly important for babies, since they are not born with the ability to fight off all germs on their own.

Samantha Lewiston, 2021 Doctor of Pharmacy Candidate, University of Wisconsin-Madison School of Pharmac, and Barbara Young, Pharm.D.

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