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Published: January 1, 2026

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A breakthrough infection is an infection that occurs in a person who has been vaccinated against that disease.

Breakthrough infections can happen because no vaccine prevents every infection, immune protection can change over time, and pathogens can evolve. A breakthrough infection does not automatically mean a vaccine failed completely; many vaccines still reduce the risk of severe illness, hospitalization, or death even when infection occurs.

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About the Author: Dr. Jay Varma

Dr. Jay Varma is a physician and public health expert with extensive experience in infectious diseases, outbreak response, and health policy.