August 11, 2025 - By Jeanna Vazquez, jbvazquez@ucsd.edu - Raising children, teens and young adults can be some of the most rewarding times in a person’s life, and also the most challenging. While many say the days are long and the years are short, families experience wonderful memories while growing together and, at times, parents face important decisions for the health and well-being of their children.

When the time comes for a child to begin receiving vaccines, parents often have questions about recommended immunizations.

Vaccines help the body’s immune system develop antibodies that can then protect a person against certain diseases should they be exposed later in life. Without vaccines, children and vulnerable individuals, such as senior adults or those with lowered immune systems are at high risk for becoming seriously ill or dying from childhood diseases, such as measles or whooping cough.

In observance of National Immunization Awareness Month, Leah Kern, M.D., assistant professor of pediatrics at University of California San Diego School of Medicine addresses common questions about vaccines, provides information on safety and efficacy and explains why they are important for individuals and the health of our community.

Why are vaccines necessary?

Vaccines are important because they teach our bodies how to prevent infections before they occur. Vaccines protect our children from getting very serious diseases that can cause problems like brain damage or, in more severe cases, death. Vaccines also help our children stay healthy so that they grow up and live full, active lives. Vaccines are like giving the body a practice run — it’s like training for a big game or practicing an instrument for a performance; they work to keep our children and teenagers healthy in order to stay active in active in schools, neighborhoods and communities.

Are vaccines safe?

Yes, vaccines are very safe. Each vaccine goes through vigorous research and clinical studies by scientists around the world before they are provided to the general community. These researchers continue to watch for side effects, even after vaccines are approved for human use by licensing organizations, such as the U.S. Food & Drug Administration (FDA) in the U.S. Millions of children and adults receive vaccines every year without serious problems. The most common side effects are mild, like a sore arm or a slight fever.

How are vaccination schedules organized to space out certain vaccines at children’s well-visits?

Scientists and doctors create vaccine schedules to give shots at the safest and most helpful times in a child or teenager’s life. The recommended vaccine schedule balances the goal of protecting the youngest infants and teens, or those who are at highest risk with making sure that their immune system develops strong protection to last as long as possible. Some shots are given together because infants and children are at the highest risk from certain diseases and their immune systems are strong enough to handle multiple vaccines at once.

How is the vaccine schedule determined?

Vaccines are scheduled to protect infant, children or teenagers early, before they come into contact with serious diseases. The schedule is based on research showing when each vaccine works best and keeps our children the safest.

What diseases do vaccines help prevent?

Vaccines protect children from many contagious diseases, including: