In 1918 a flu pandemic killed between 20 million and 40 million people worldwide.

In 1957 and 1968 there were pandemics that killed over 500,000 people each year.

This is what researchers are afraid of now. If it doesn't turn into a pandemic this year, they think that it will happen within the next few years.

This year they made 83 million doses of the flu vaccine, and the US population is currently about 292,800,000, so only 28% of the population was able to get protected this year.