What is the best (scientific) way to boost the immune system?

Answer 1

The best ways are:
get your yearly flu vaccine
get a tetanus shot every 10 years
eat a healthy diet involving all the food groups
reduce stress (the biggest threat to the immune system)
moderate exercise
adequate sleep
certain foods boost your immunity (chicken soup, green tea, blueberries, broccoli)
music (studies have show that music decreases stress)
and, most of all, frequent handwashing!