Why We Need a New Flu Vaccine Every Year

Flu viruses are quick change artist. They constantly need to take and those frequent changes make it hard for our bodies to recognize and fend off the virus. That's why we need a new flu vaccine every year. The outside of influenza A viruses are studded with two proteins called hemagglutinin and neuraminidase. 

There are many versions of these proteins the combinations of each H and in give fluids name like with a common H 3 and 2 and H1N1 viruses that are part of every year's flu vaccine and helps the virus attached to cells in the nose throat or lungs key to getting infected if the immune system recognizes a particular hemagglutinin from either an earlier infection. 

Vaccination it will produce flu fighting antibodies to block the virus from latching on as influenza virus spreads. It gradually undergoes subtle genetic mutations, eventually with enough changes defense has the body built in the past can no longer recognize current strains that's called antigenic Drift and it's why the flu vaccine gets an annual update but every so often influenza undergoes a sudden major genetic change resulting in a flu strain so different that Most people have little or no immunity like during the 1918 Spanish Flu pandemic pandemics can happen if a virus carried by a bird or a pig mixes and swaps genetic material with a typically human strength infecting people with a novel virus that's called an antigenic shift sometimes an animal strange. I'm strictly into a human Global Health experts decide the recipe for each year's flu vaccine based on predictions of which strains are most likely. 

To be spreading the following winter and hope the flu doesn't drift enough that season to spoil the match seasonal flu vaccines won't protect people in a pandemic now scientists are working to create a universal vaccine that might one day protect against both kinds of flu evolution. 

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