Getting insufficient sleep in the days before or after a vaccination could weaken its effectiveness particularly for men, a new study has found.

Researchers from the U.S., France, the U.K. and Sweden conducted the study, which was published in the journal Current Biology on Monday.

Men who reported getting six or fewer hours of sleep per night in the days before and after getting vaccinated showed a significant reduction in antibody response. 

Women did not show that same association — although more data is needed.

PRIOR COVID INFECTION PROVIDES JUST AS MUCH PROTECTION AS VACCINES, NEW STUDY FINDS

Pulling data from seven past studies in the PubMed database, researchers evaluated the antibody responses to influenza and hepatitis vaccines among 299 adults between the ages of 18 and 60. 

(They excluded adults 65 years and older, as that age group generally has reduced quality and duration of sleep.)

"It is well-known that sleep plays an important role in regulating the immune system," study co-author Aric A. Prather, PhD, professor of psychiatry and behavioral sciences at the University of California, San Francisco, told Fox News Digital in an email. 

"How that happens is not well understood, but data suggests that aspects of sleep — like slow wave sleep, or the hormones released during sleep, like growth hormones — may directly communicate with the immune system to support protection."

He added, "The key takeaway is that there is compelling evidence that insufficient sleep dampens our immune system’s capacity to mount protective antibodies following vaccinations."

IRREGULAR SLEEP COULD PUT YOU IN THE DANGER ZONE FOR HEART DISEASE, SAYS STUDY

Dr. Marc Siegel, clinical professor of medicine at NYU Langone Medical Center, was not surprised by the study's findings (he was not involved in the study), given sleep's proven connection to the immune system. 

"Studies have shown that people who don’t get sufficient or full-quality (deep REM) sleep are more susceptible to viral infections if exposed," he told Fox News Digital. 

"Lack of sleep also impacts recovery time from illness."

Dr. Prather was not expecting such a big gender difference in antibody response.

"There are some data to suggest that vaccines work differently in men and women, with some data to support an advantage for women, including for the COVID-19 vaccine," he said. 

"However, this meta-analysis suggests that men who get insufficient sleep are more likely to experience suboptimal vaccination response compared to women."

In a discussion of the findings, the study authors said the lesser impact of sleep on women’s antibodies was "likely due to the wide variations in sex hormone levels according to the phase of the menstrual cycle, use of hormonal contraception, menopausal status and use of hormonal replacement in post-menopausal women."

There are not yet any similar studies looking at the connection between sleep and COVID-19 vaccines.

Yet the researchers estimated that insufficient sleep in the days surrounding a COVID vaccine could result in reduced antibodies similar to what would be seen two months after receiving the jab.

The researchers looked at two different types of studies: self-reported, where the participants submitted their own sleep patterns, and objective, where the participants’ sleep was tracked by special devices or in a sleep lab.

SOME 20% OF AMERICANS ARE TAKING SLEEP MEDICATIONS, CDC SAYS: 'ALARMING' DATA

The self-reported studies found that although there was a reduction in antibodies for those who slept for less than six hours, it was not "statistically significant."

For the objective studies, there was a "robust decrease in antibody response" for men, the findings stated.

The study authors suggested that this may be due to people in the self-reported studies overestimating the number of hours they slept.

Dr. Prather noted that only a handful of studies have tackled the relationship between sleep and vaccination response.

Also, he said more research is needed to determine the specific windows of time when sleep might be most important. 

"For instance, it may be that sufficient sleep on the nights prior to or after vaccination provides a unique benefit," he told Fox News Digital. 

"For example, we found that short sleep duration on the two nights prior to the influenza vaccine was critical in predicting antibodies months later." 

YEARLY COVID VACCINE AS PROPOSED BY FDA? 'CART BEFORE THE HORSE,' SAYS DOCTOR

The researchers also called for more research to determine the optimal amount of sleep for antibody response and the reason for the significant difference in sleep impact between genders.

"Collecting information about sleep duration around the time of vaccination and about sex hormone levels in the millions of people who will receive vaccines and boosters against COVID-19 and other viruses is an unprecedented opportunity to study the role played by sleep duration in vaccine response," the study authors wrote.

CLICK HERE TO SIGN UP FOR OUR HEALTH NEWSLETTER

The National Sleep Foundation recommends that adults between 18 and 64 get seven to nine hours of sleep per night.

The Centers for Disease Control and Prevention warns on its website that lack of sleep is linked to several serious conditions, including type 2 diabetes, heart disease, obesity and depression.

"Bottom line: Get good sleep if you have a vaccine coming up and also right after you get it," Dr. Siegel recommended.