New Flu Vaccines Arrive, But a Common Virus Strain Is Missing

The 2024-2025 flu season is kicking off with a new vaccine, but this year’s shot has an unusual twist: it will target only three strains of the influenza virus, not four. This adjustment comes as the B/Yamagata lineage, one of the typical components of quadrivalent flu vaccines appears to have vanished.

What’s Missing?

According to the National Institutes of Health (NIH), the B/Yamagata virus strain hasn’t been detected in the global flu surveillance network since 2021. While the reason for its absence isn’t confirmed, experts believe widespread masking and social distancing during the COVID-19 pandemic may have severely diminished or even wiped out this strain. Despite the speculation, public health officials have not officially declared the virus extinct, and some caution that it could still resurface.

Vaccine Composition

This season’s flu vaccine will offer protection against three main strains:

• Influenza A(H1N1) pdm09
• Influenza A(H3N2)
• Influenza B/Victoria

The shift from four to three strains reflects the absence of the B/Yamagata virus. Influenza vaccines are updated each year to keep up with the virus’s rapid evolution, and experts work to predict which strains are most likely to circulate.

Flu Season: Stay Prepared

Flu season typically runs from October to May, with peak activity expected between December and February. Health authorities stress the importance of getting vaccinated early to maximize protection. Even with changes to the vaccine’s formula, it remains a crucial defense against serious illness, hospitalizations, and complications from the flu.

Get your flu shot soon and take precautions to stay healthy this winter!