If you haven’t been sleeping well, you’re likely to be tired a lot of the time, have headaches and gain weight. Not surprisingly, your eyes may be red, your hands may shake, and you could be at increased risk of high blood pressure. But did you know that individuals who don’t get enough sleep may also be more prone to colds and flu? To find out whether lack of sleep affects how well vaccines work, researchers recruited 70 women and 55 men between age 40 and 60. All of the participants were given the hepatitis B vaccine, which is administered in three doses, two given a month apart and a booster after six months. The researchers tested the volunteers’ antibody levels before the second and third shots of the vaccine and then six months after their last shot. The study showed that the volunteers who didn’t sleep more than six hours a night were 11.5 times less likely to be protected by the vaccine than those who slept at least seven hours a night. The study was published in the August 2012 issue of SLEEP.