To make flu shots effective, sleep specialist Matthew Walker, author of “Why We Sleep,” told CNN’s Christiane Amanpour practicing good sleep hygiene is important.

Insufficient sleep in the week before getting a flu shot can lead to the production of less than 50% of the normal antibody response — a reaction that would render the flu shot largely ineffective, Walker told Amanpour. Walker specializes in the relationship between sleep and human health at the University of California, Berkeley.