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Does sleep affect your immune system?

Last updated: October 15, 2026

Yes. In one study, staying awake from 3 to 7 AM for a single night lowered natural killer cell activity by about 28% the next day. Short sleep is also linked to catching colds more easily and to weaker responses to vaccines.

The cold-risk study

Prather et al. (2015) measured the sleep of 164 healthy volunteers for a week, then gave them nasal drops containing a cold virus. Those who had slept 5 to 6 hours a night were about 4.2 times more likely to develop a cold than those sleeping more than 7 hours, and 4.5 times for under 5 hours.

Vaccine response

In a small study, people whose sleep was restricted around a flu shot produced a weaker antibody response in the days that followed (Spiegel et al., 2002). The vaccine still worked, but the response was slower to build.

The mechanism

Natural killer cell activity fell to 72% of normal after one shortened night, then recovered after a normal night of sleep (Irwin et al., 1994). Sleep loss is also linked to higher levels of inflammatory markers, which may lower resistance to infection.

Sources

1. Prather et al., Sleep, 2015. Behaviorally Assessed Sleep and Susceptibility to the Common Cold
2. Irwin et al., Psychosomatic Medicine, 1994. Partial sleep deprivation reduces natural killer cell activity in humans
3. Spiegel et al., JAMA, 2002. Effect of sleep deprivation on response to immunization