A wide body of research suggests that those who skimp on sleep are more likely to develop a chronic disease such as diabetes or respiratory infections. Now a new study from the University of Pittsburgh suggests that those who are sleep-deprived also don’t get the full immune response from vaccinations, which could leave them susceptible to diseases that they’re vaccinated against.

The study published last week in the journal Sleep examined the immune responses in 125 adults ages 40 to 60 who received a vaccine against hepatitis B and found that those who slept fewer than six hours a night around the time they received the vaccine had a higher risk — 11.5 times higher — of remaining unprotected from the virus six months later than those who slept seven or more hours a night.

Nearly 15 percent of the study participants failed to obtain protection from the vaccine six months after they received all three injections in the series.

The study couldn’t prove that lack of sleep reduced the antibody response to the vaccine since it merely observed sleep patterns — through self-reports and sleep lab studies conducted just before the vaccine was administered — and made a statistical association between sleep time and the participants’ immune response to vaccines. It does, though, provide further evidence that skimping on sleep isn’t great for the body. Bottom line: aim for seven to eight hours a night.