Last updated August 20, 2026
Public health communicators are increasingly receiving questions about why children receive multiple vaccines during the first few years of life. The recommended childhood immunization schedule from the American Academy of Pediatrics (AAP) is designed to protect children when they are most vulnerable to serious diseases.
The AAP immunization schedule is endorsed by a broad group of leading medical and health organizations, representing pediatricians, family physicians, nurses, pharmacists, infectious disease specialists, and other health care professionals. Communicators can help build understanding by explaining how the schedule is developed, why vaccines are recommended at specific ages, and how children’s immune systems respond to vaccines.
The childhood immunization schedule is designed to protect children when they are most vulnerable.
- Babies and young children are at higher risk for serious illness because their immune systems are still developing.
- Diseases such as measles, whooping cough (pertussis), pneumococcal disease, and meningitis can lead to hospitalization, long-term complications, or death in young children.
- Vaccines are recommended before children are most likely to be exposed to these diseases, helping them build protection that is ready when they need it most.
- Delaying recommended vaccines or skipping recommended doses extends the period during which children remain vulnerable to preventable diseases.
Children’s immune systems are built to respond to vaccines.
- From birth, children’s immune systems respond to thousands of bacteria and viruses through everyday activities like eating, breathing, crawling, and playing.
- Vaccines contain only a small number of antigens — the parts of a virus or bacteria that train the immune system to recognize disease. Although children receive more vaccines today than in previous generations, today’s vaccines contain fewer antigens than older vaccines.
- A healthy child’s immune system can respond to multiple vaccines during the same visit, while continuing to respond to the many germs encountered every day.
- Receiving recommended vaccines during the same appointment helps children build protection sooner while reducing the number of healthcare visits families need to make.
Every vaccine and every recommended dose serves a specific purpose.
- Each vaccine protects against a different disease that can cause serious illness during infancy and childhood.
- Some vaccines require multiple doses because the immune system develops stronger, longer-lasting protection over time. Getting only one of multiple doses, or delaying the recommended time between doses, will not provide the full protection needed to prevent serious illness.
- The timing of each vaccine and each dose is based on when children are most likely to benefit from protection, ensuring children get the right protection at the right time.
- Delaying or spreading out vaccines can leave children unprotected for longer without providing any proven benefit. The recommended schedule is designed to protect children at the ages when they are most vulnerable while minimizing unnecessary visits and missed opportunities for vaccination.
The childhood immunization schedule reflects decades of research and ongoing review.
- The recommended schedule is informed by decades of research on childhood diseases, immune system development, and vaccine performance.
- Researchers evaluate when children are most likely to be exposed to diseases, how well vaccines work at different ages, how long protection lasts, and whether vaccines can be given during the same visit.
- Vaccine recommendations are regularly reviewed and updated as new information becomes available. For example, after reviewing data showing that one dose of varicella vaccine did not provide enough protection to prevent all cases and outbreaks, the AAP updated its guidance to recommend a routine two-dose varicella vaccine schedule for children.
- The schedule is designed to provide children with protection at the ages when vaccines offer the greatest benefit.
Vaccination helps children, families, and communities thrive.
- Staying up to date on recommended vaccines helps reduce the risk of serious illness, hospitalization, disability, and death from vaccine-preventable diseases.
- Vaccination helps children spend more time learning, playing, and growing.
- Babies may be too young to receive certain vaccines, so they also rely on those around them, including older children, to get vaccinated to prevent the spread of disease. Keeping communities protected against vaccine-preventable diseases helps reduce outbreaks and protects those at greatest risk of severe illness.
Sources
Children’s Hospital of Philadelphia Vaccine Education Center. The Science Behind the Vaccine Schedule.
American Academy of Pediatrics (AAP). All About the Recommended Immunization Schedule.
American Academy of Pediatrics (AAP). Prevention of Varicella: Recommendations for Use of Varicella Vaccines in Children, Including a Recommendation for a Routine 2-Dose Varicella Immunization Schedule.
