How are annual flu vaccines made?
Immunologist Zachary Rubin explains how the World Health Organization decides which flu strains go into annual flu vaccines.
This video is part of “Innovations in: RSV», an editorially independent special report, produced with the financial support of MSD, Sanofi And AstraZeneca.
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Zachary Rubin: Did you know that your flu vaccine was designed over six months ago? Yes, before the first cough, before the onset of cold weather, scientists around the world are already trying to get ahead of the virus. Here’s how it works.
Twice a year, the World Health Organization brings together global experts to review flu surveillance data. They look at which flu strains spread during winter in the southern hemisphere, in countries like Australia, Chile and South Africa, and use that data to predict which strains will likely dominate during the northern hemisphere’s flu season. They recommend including three to four strains in the annual flu vaccine, and that decision is made months before the vaccines reach your pharmacy.
Once the varieties are selected, the manufacturers get to work. In the United States, most flu vaccines are still egg-based, meaning the virus is actually grown in fertilized chicken eggs. The virus is then harvested, inactivated, purified and formulated into a vaccine.
But new methods are changing the situation. Cellular vaccines grow viruses in animal cells, not eggs. And recombinant vaccines completely skip the growth stage of the virus: they use genetic engineering to quickly produce proteins that boost your immune system without needing the full flu virus. These newer methods are faster, can offer more precision, and do not require millions of chicken eggs each year.
Even in years when compatibility is not perfect, the flu vaccine prevents millions of illnesses and thousands of hospitalizations and deaths. And because the flu spreads even before symptoms appear, protecting yourself helps protect your entire community.
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