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Questions and Answers About the Vaccine Schedule

The recommended immunization schedule is endorsed by three agencies: the Centers for Disease Control and Prevention (CDC), the American Academy of Pediatrics (AAP) and the American Academy of Family Physicians (AAFP). The endorsement of these agencies is based upon recommendations of groups of scientists, physicians and public health officials. These experts review information related to two main areas of interest:

By understanding all of these factors, experts can confidently compose an immunization recommendation that is safe and well tested.

How can a single schedule be appropriate for all children?

Although there is only a single recommended schedule, the recommendations incorporate specific information for sub-groups of the population. The schedule informs providers that some people should or should not receive a vaccine based on factors related to:

How can a baby get the same dose of a vaccine as an older child or adult?

Because vaccines do not work like medications, in many cases the same vaccine dose can be given to different age groups; however, in some cases, different versions of vaccines are available for different age groups.

Why are several doses of some vaccines needed?

The number of necessary doses of a particular vaccine depends on many factors including the type of vaccine, the amount of disease in the community and how the immune system works:

Wouldn’t it be better to get diseases naturally?

If you could see the world from the perspective of your immune system, you would realize that where the virus or bacteria comes from is irrelevant. Your immune system “sees” something that is foreign, attacks it, disables it and then adds it to the memory bank so it can react more quickly the next time it encounters it.

The differences between a vaccine and getting the disease naturally are the dose and the known time of exposure.

So, in summary, a vaccine affords us protection with lesser quantities of virus or bacteria and the control of scheduling the exposure.

When is it okay to change the vaccine schedule?

Children with certain health conditions or illnesses may need to get vaccines at slightly different times than their peers. Healthcare providers refer to these changes as precautions and contraindications:

If you are concerned about a condition that might be a reason to delay or withhold vaccines, talk to your healthcare provider or contact your local health department.

Why does the vaccine schedule change?

Changes to the immunization schedule can be the result of new (e.g., HPV vaccine for girls) or improved vaccines (acellular pertussis vaccine), changes to the group of people most susceptible to the disease (hepatitis A vaccine), changes to the virus (H1N1 influenza vaccine), or new data about vaccine efficacy (HPV vaccine for boys).

Scientists and public health officials are dedicated to understanding and monitoring diseases and the vaccines being used to prevent them. As a result, the immunization schedule is updated regularly. For this reason, it is a good habit to check with your healthcare provider at every visit about whether you or your family members should get any vaccines.

What is the “catch-up” schedule?

If doses of vaccine need to be delayed or are missed, the catch-up schedule gives healthcare providers the information necessary to safely get a child up to date. Vaccines may have been missed due to vaccine shortages, new or revised vaccine recommendations, or changes in health status that no longer make previous contraindications or precautions necessary. A good habit to develop is to check with your healthcare provider during every visit whether any vaccines can be given.

Reviewed by: Paul A. Offit, MD
Date: April 2013

Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health. You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel.


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