1. Why is the seasonal flu not considered a pandemic?
2. With how much we know about the flu and the vaccines and treatments we have for it, why are the deaths related to the flu in the U.S. each year still around 40,000 people?
We see epidemics, localized outbreaks, if seasonal flu exceeds what is called the threshold which is a rise in cases above a certain number along with how severe these cases are. We usually do have flu epidemics each year. But a pandemic is a much more severe flu affecting more of the population worldwide. Pandemics are usually caused by flu viruses that are unique to the population.
We know a lot about the flu and vaccines but sometimes the components of the vaccine which are the antigens for a particular flu virus are not the right choice for the flu viruses that actually circulate that year. It's an educated guessing game. Most people do not get the flu vaccine.