eli5-Flu shots if they are the wrong strain

Question

Flu shots are made up of what they think the next major strains will be, however they are wrong a majority of the time. Why do we still get them? Full disclosure, I still get them.

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Answer 1

> they are wrong a majority of the time

The flu is not one thing. There are many different strains (variants) the influenza virus that causes the flu, and, because it is a virus that evolves rapidly, new strains are always emerging and being discovered. This makes predicting which strains will be spread broadly among a population challenging.

While a particular year’s annual flu vaccine is not going to protect you against *all* the strains of influenza or be a 100% guarantee that you won’t get the flu *at all*, it reduces your chances significantly by providing you immunity to some, but probably not all, strains.

If you look at [the data provided by the US Center for Disease Control](https://www.cdc.gov/flu/vaccines-work/vaccineeffect.htm), getting an annual flu shot reduces your chance of getting the flu **by 40-60%** depending on a number a factors included age and health. Probably more importantly, even if you do get infected with the influenza virus, being vaccinated have been empirically show to reduce the severity of infections, number of hospitalizations, and number of deaths in the population. In summary: your chances are better with a vaccine than without.

> Why do we still get them?

1/ Because expecting any vaccine to be 100% effective is ignorant and misinformed. A 40-60% reduction in risk is fantastic and, for many people, life-saving. Especially for a virus that mutates as frequently as influenza. You get them because the risk is extremely low (you’re at more risk of death or injury just driving to work every day), and the potential upside is, you know … *not dying*. That’s a pretty good return on investment. Vaccination is a way to protect yourself.

2/ The purpose of a vaccine is not to eradicate a disease *by the vaccine.* Rather, the purpose of a vaccine is to increase a population’s immunity to a disease in order to decrease the spread of a disease. Your immunity to strain *x* of a virus means that you won’t spread (or will spread less) of that virus to more vulnerable people. Vaccination is a way to protect others.