While scientists are still learning about the relationship between sleep and the immune system, getting adequate rest could become a factor in the effectiveness of the COVID-19 vaccine, as well.
Here’s why you should rest up before getting the flu shot and other vaccines.
How Sleep Impacts Vaccines
Vaccines work by introducing the immune system to a small amount of a particular virus or bacteria so that our immune systems can learn to produce antibodies specific to those pathogens and fight them off.
Sleep (or a lack of rest) can impact how well our immune system functions, including antibody production. That means vaccines may be more (or less!) effective in our bodies depending on whether we’re well-rested or sleep-deprived, especially around the time of the shot. Science hasn’t conclusively proven this connection, but early research supports the possibility.
For instance, in March 2020, scientists published the results of a study on 83 young adults who kept sleep diaries two days before and 11 days after getting the flu vaccine. The researchers tested participants’ blood one month and four months after the vaccine and found that those with a shorter average sleep duration (especially in the two nights before the shot) developed fewer antibodies to the flu virus compared with those who slept longer.
This study echoes the findings of earlier research. In 2016, the first study to explore the relationship between insomnia and the immune response to the flu vaccine found that people with insomnia or otherwise poor sleep quality tended to have lower influenza antibody amounts than good sleepers.
And in 2002, another study found that men who had a sleep debt at the time of their flu vaccine developed fewer than half the antibodies 10 days later as those who had “normal” sleep times. However, both groups had similar antibody levels three to four weeks after the vaccination, indicating that lack of sleep may only impact the short-term immune response.
It’s not just the flu shot that seems to be affected by sleep, though. In 2012, researchers looked at how 125 people between the ages of 40 and 60 responded to the three-dose hepatitis B vaccine and found that those who slept less around the time of the vaccines had a lower likelihood of being protected from the disease. Similarly, a 2003 report found that people who had regular sleep the night after receiving the hepatitis A vaccine had twice as many antibodies to the disease after four weeks compared with people who pulled a post-vaccine all-nighter.
These studies could offer clues as to how sleep may play a role in how well our bodies respond to the forthcoming COVID-19 vaccines, as well.
“The evidence so far means that it’s very likely the amount of sleep you get around the time of the vaccine will influence your antibody levels,” says Dr. Matthew T. Scharf, assistant professor of medicine and neurology at the Rutgers Robert Wood Johnson Medical School and medical director at RWJ Sleep Laboratory Comprehensive Sleep Center. “Without being able to say definitively, it seems reasonable to make sure people get enough sleep around the time of the vaccine to promote maximum effectiveness.”
Sleep and the Immune System
While multiple studies have shown a relationship between sleep deprivation and antibody response to vaccines, scientists have yet to figure out the reason behind this immune response.
“The immune system is like an orchestra. If you want to produce a piece of music, you need every element coordinated in a certain way,” says Dr. Scharf. “In order for the immune system to function properly, one of the major modulators of that is sleep and the circadian rhythm.”
The hormonal fluctuations that occur while we sleep — specifically an increase of the growth hormone prolactin and a decrease in the stress hormone cortisol — may facilitate certain immune responses, such as antibody production after a vaccine, says Dr. Scharf. Without enough quality sleep, the body’s ability to build a defense against certain diseases seems to be impaired.
“You presumably get a more robust activation of the immune system because of this hormonal milieu that occurs during sleep,” explains Dr. Scharf. “There’s a fair amount of experimental evidence to support that.”
There may also be a genetic link that explains the effect of sleep on vaccinations, says Dr. Nathaniel Fletcher Watson, professor of neurology at the University of Washington School of Medicine and co-director of the UW Medicine Sleep Center. His research on twins has uncovered some evidence that the amount of sleep you get may impact the influence of certain genes on your health.
“Any given aspect of our physiology is driven by genetic transcription and translation to create proteins that allow the body to function,” says Dr. Fletcher Watson. "When there’s sleep deprivation, there appears to be some down-regulation of the transcription of immune-related genes."
How Much Sleep to Get Before a Vaccine
The jury’s still out on exactly how much sleep people should get leading up to a vaccine, but, generally speaking, you should aim for at least seven hours a night, says Dr. Watson.
“You’re going to do better if you’re getting healthy sleep. We define that as seven or more hours of sleep on a nightly basis to support optimal health,” he explains.
Pay particular attention to how much rest you’re getting in the few days before and after a vaccine. Based on recent studies, those days seem to play a bigger role in affecting your body’s ability to produce antibodies, says Dr. Scharf.
That being said, it’s not necessarily a great idea to postpone your flu vaccine (or any other doctor-recommended vaccination) if you’re having trouble sleeping in a given week.
“If someone puts it off, the next thing is they forget about it and don’t get it,” says Dr. Watson. “It doesn’t mean there may not be opportunities to have a better immune system if you get vaccinated under different circumstances, but realistically, just getting it done will be much more impactful on your health over the long term.”