What is vaccine strain mismatch?
Quick Answer
Vaccine strain mismatch happens when the strains included in a vaccine do not closely match the strains circulating in the population. This can reduce how well the vaccine works.
The Full Story
Strain mismatch is a major issue for viruses that mutate often, especially influenza. Flu vaccines are updated regularly because the virus changes from season to season, and the strains selected for the vaccine may not perfectly match the viruses that actually spread. When the match is poor, the vaccine may still offer partial protection, especially against severe disease, but effectiveness can be lower. This is one reason annual flu vaccination is recommended. Strain mismatch illustrates why some pathogens require continual surveillance and reformulation.
Key Facts
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"What happens when a vaccine and a virus don’t quite match?"
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