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Some people wonder why most vaccines require multiple doses. The reasons vary depending on the vaccine.
Reason for multiple doses
- To protect those who didn’t respond to the first dose. Example: chickenpox vaccine
- Additional doses provide a greater immune response than that generated after the first dose. Example: Haemophilus influenzae type b vaccine
- The immune response lasts longer after more than one dose is received. Example: Pertussis vaccine
- The vaccine protects against a virus that changes enough so that immunity to older versions wouldn’t be protective. Example: Influenza vaccine
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.