Tag Archives: seasonal

How Seasonal Rhythms of the Body Clock Influence Vaccine Effectiveness

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Understanding Seasonal Immune Response

Timing of Children’s Polio Vaccination Affects Immune Strength.

Bilawal Arbab/EPA-EFE/Shutterstock

Many individuals notice fluctuations in their health correlating with seasons. Recent studies reveal that vaccine responses—and, broadly, our physiological characteristics—vary throughout the year.

While humans are not generally categorized as seasonal beings, many plants and animals adhere to biological calendars that dictate behaviors such as flowering, reproduction, migration, and hibernation. Over the last decade, research has unveiled that humans experience subtle seasonal changes in immune activation, hormone levels, and gene expression.

“The most intriguing discovery from this research isn’t just about vaccines, but rather human immune function. It varies by season,” states Kathy Wyse from the University of Edinburgh, who did not participate in the study. “This indicates that humans may possess an inherent seasonal timing mechanism, akin to that observed in animals and birds.”

Research indicates that the response to influenza vaccines adheres to a 24-hour circadian rhythm. Laura Valero Guevara and her team at New York University explored the implications of seasonality on vaccine effectiveness.

The team analyzed data from 96 randomized controlled trials involving approximately 48,000 children vaccinated against 14 infectious diseases, including measles, polio, and chickenpox. These studies, held in various countries at different times of the year, allowed for a comprehensive comparison of seasonal and geographic differences in immunogenicity—the immune response strength provoked by vaccination.

“We indeed observed a seasonal immune response,” Valero-Guevara shared. “What’s particularly exciting is the latitudinal gradient we noticed. In temperate zones, both in the Northern and Southern Hemispheres, stronger immune responses occurred in the winter, likely influenced by seasonal variations in light exposure.”

As proximity to the equator increased, the immune responses appeared to follow a less predictable seasonal pattern. There remained significant annual fluctuations in vaccine reactions within tropical regions; while some vaccines, like rotavirus and polio, showed marked seasonal variations. However, unlike the consistent winter peaks seen in temperate areas, tropical peak responses varied depending on the specific vaccine.

The researchers excluded any children with pre-existing antibodies against the pathogens prior to vaccination, indicating that recent exposure to infections is unlikely to account for these findings.

However, the underlying causes of these variations remain elusive. “Initially, we posited that seasonal circadian rhythms prompted by changes in light exposure drive these variations. This would imply that the amplitude of seasonality should be less pronounced in tropical areas compared to temperate regions,” said Mathieu Domenech de Sel from the Max Planck Institute for Infection Biology in Berlin. “But that’s not what we found, so other factors, or a combination of light exposure and other influences, might be at play.”

Past research has suggested seasonal patterns in immune activity. In 2020, Wyse and her colleagues reported seasonal variations in inflammatory markers, revealing different immune cell types peak at varied times—some in winter, others in spring.

Additionally, Manuel Ilima and his team at the Genome Control Center in Barcelona identified seasonal patterns in gene expression across multiple human tissues, including hormone-regulating areas of the brain and testes, along with numerous immune-related genes. “While we still lack a clear understanding of the mechanisms, the new findings could be tied to our observations,” suggests Iruma.

Weiss posits that humans may possess an inborn seasonal timing system influenced by variations in daylight. “This mechanism is also revered in animals, birds, and fish, even if we haven’t conclusively demonstrated it in humans yet,” he explains.

Thought to be located in the hypothalamus—which houses the suprachiasmatic nucleus that regulates circadian rhythms—this timing system adapts differently in equatorial animals, where day length stability weakens annual cycles, redirecting ecological reliance towards environmental factors like food availability or rainy seasons.

Evidence suggesting seasonal patterns in humans could extend beyond the immune realm. Earlier this year, Timothy Hearn at the University of Cambridge with David Whitmore of University College London reported that births in Britain exhibited a notable seasonal rhythm, peaking during spring throughout much of the 20th century, until a significant change in the 1970s due to widespread contraceptive access.

Professor Hahn emphasizes that dismissing evidence of seasonal biology in humans is becoming increasingly challenging, but disentangling whether these rhythms represent an inherent biological calendar is complex. “The term ‘season’ encompasses a range of interconnected environmental interactions, along with related shifts in disease exposure, diet, activity, sleep, and social behaviors.”

If the seasonal variations identified by Valero-Guevara and her team are validated, it may prompt considerations around optimizing vaccination schedules based on seasonal health patterns.

Nonetheless, Professor Weiss cautions that differences in antibody responses may not directly translate to significant variances in vaccine efficacy, implying that delaying vaccinations for potential immune improvements could pose greater risks. “Postponing vaccination for a month to target winter could be more hazardous than anticipated,” she states. “Current evidence does not substantiate such an approach.”

“Ultimately, time will determine if there are clinical advantages in scheduling vaccinations seasonally,” she adds. “Presently, the evidence is insufficient to support this.”

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Source: www.newscientist.com

Planetary Scientists Discover Seasonal Ozone Layers Formed by Mars’s Arctic Vortex

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Polar water is generated during the Martian season, which occurs due to the planet’s axis being tilted at an angle of 25.2 degrees, as explained by Dr. Kevin Olsen from Oxford and his colleagues at Latmos, CNRS, CNRS, Space Research Institute, Open University, and NASA.

This perspective view of Mars’ Arctic Ice Cap showcases its unique dark troughs arranged in a spiral pattern. The image is derived from observations made by ESA’s Mars Express, utilizing elevation data from NASA’s Mars Global Surveyor’s Mars Orbiter Laser Altimeter. Image credit: ESA/DLR/FU Berlin/NASA/MGS/MOLA Science team.

“The polar vortex’s atmosphere, extending from near the surface to around 30 km high, experiences extremely low temperatures, approximately 40 degrees Celsius lower than the surrounding area,” stated Dr. Olsen.

“In such frigid conditions, most of the water vapor in the atmosphere freezes and accumulates in the ice cap, resulting in ozone formation within the vortex.”

Normally, ozone is destroyed by reacting with molecules generated when ultraviolet radiation decomposes water vapor.

However, once all water vapor is depleted, there are no reactive molecules left for ozone, allowing it to accumulate in the vortex.

“Ozone plays a crucial role for Mars. It is a reactive form of oxygen that indicates the pace of chemical reactions occurring in the atmosphere,” Olsen noted.

“By investigating the levels of ozone and their variances, we gain insight into how the atmosphere evolves over time and whether Mars once had a protective ozone layer similar to Earth.”

Slated for launch in 2028, ESA’s Rosalind Franklin Rover aims to uncover evidence of life that may have existed on Mars.

The possibility that Mars had a protective ozone layer, safeguarding its surface against harmful ultraviolet radiation from space, enhances the likelihood of ancient life-sustaining conditions on the planet billions of years ago.

Polar vortices are produced during the Martian season as a consequence of the axial tilt of 25.2 degrees.

Similar to Earth, an atmospheric vortex forms above Mars’ North Pole at the end of summer and persists through spring.

On Earth, polar vortices can destabilize, losing their structure and shifting southward, often bringing cold weather to mid-latitudes.

A similar phenomenon can occur with Mars’ polar water vortex, which provides an opportunity to explore its internal dynamics.

“Studying the Northern Pole’s winter on Mars presents challenges due to the absence of sunlight, akin to conditions on Earth,” Dr. Olsen explained.

“By analyzing the vortex, one can differentiate between observations made inside and outside it, providing insight into ongoing phenomena.”

The atmospheric chemical suite aboard ESA’s trace gas orbiter examines Mars’ atmosphere by capturing sunlight filtered through the planet’s limb while the sun is positioned behind it.

The specific wavelengths of absorbed sunlight reveal which molecules are present in the atmosphere and their altitudes above the surface.

Nonetheless, this method is ineffective during the complete winter darkness on Mars when the sun does not illuminate the Arctic region.

The only chance to observe the vortex is during moments when its circular shape is lost, but additional data is required to pinpoint when and where this occurs.

To enhance their research, the scientists utilized NASA’s Mars Reconnaissance Orbiter’s Mars Climate Sounder instrument, measuring temperature variations to gauge the vortex’s extent.

“We sought sudden drops in temperature, which indicate entry into the vortex,” Dr. Olsen noted.

“By comparing ACS observations with data from Mars’ climate sounders, we observed significant atmospheric differences within the vortex compared to the surrounding air.”

“This presents a fascinating opportunity to deepen our understanding of Mars’ atmospheric chemistry and how polar night conditions shift as ozone accumulates.”

The findings were presented at the EPSC-DPS2025 Joint Meeting in Helsinki, Finland, this month.

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K. Olsen et al. 2025. What’s happening in the Arctic Vortex of Mars? EPSC Abstract 18: EPSC-DPS2025-1438; doi: 10.5194/epsc-dps2025-1438

Source: www.sci.news

Research Uncovers That Humans Are Seasonal Beings

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Biological processes such as sleep, heart rate, and metabolism are regulated by the circadian clock found in nearly every cell in the human body. However, modern lifestyles challenge this natural timing mechanism in ways for which we are not well-suited. Factors like industrialization, shift work, artificial lighting, and smartphone usage significantly impact our sleep and circadian rhythms. A recent study from the University of Michigan reveals that our circadian rhythms continue to align with seasonal changes in sunlight. This result was published in the journal NPJ Digital Medicine.

Kim et al. We believe that substantial individual differences in shift work adaptation, which are vital for shift workers’ health, can be explained in part by the biological mechanisms of seasonal timing. Image credit: Sasin Tipchai.

“We may not want to admit it in today’s world, but humans are inherently seasonal,” stated Dr. Ruby Kim, the study’s lead author.

“The duration of daylight and the sunlight we receive significantly influence our physiology.”

“Our research demonstrates that the timing of biologically significant seasons plays a role in how individuals adapt to changes in their daily routines.”

“These findings could lead to new avenues for investigating and understanding seasonal affective disorders, a form of depression linked to seasonal variations.”

“It could also point to new areas of exploration regarding a range of health issues related to sleep schedules and alignment with circadian rhythms.”

“This work holds great promise for future discoveries, potentially impacting metabolic and cardiovascular health as well as mental health conditions such as mood disorders and anxiety.”

The study also indicated that humans possess a seasonal genetic component, which might explain the significant differences in how individuals are impacted by variations in daylight.

“Some individuals may adapt better, while others might fare much worse,” remarked Professor Daniel Foger, a senior author of the study.

Investigating this genetic component could help researchers and healthcare providers identify where an individual falls on the adaptation spectrum, although achieving this will require more time and effort.

For now, this study serves as an important first step in reshaping our understanding of human circadian rhythms.

“Many people tend to perceive their circadian rhythm as a singular entity,” explained Professor Foger.

“Our findings indicate that it’s not one clock, but rather two.”

“One clock tracks dawn, and the other tracks dusk. They communicate with each other.”

Researchers adjusted their studies of circadian rhythms according to seasonal sunlight by analyzing sleep data collected from thousands of participants using wearable health technology like Fitbits.

All participants were medical interns involved in a one-year internship as part of a healthcare study funded by the National Institutes of Health.

Interns are shift workers whose schedules frequently change, which also changes their sleep patterns.

Moreover, these schedules often run counter to the natural day-night cycle.

The observation that the circadian rhythm of this group demonstrated seasonal dependence is a strong indicator of how deeply ingrained this feature is in humans, which is unsurprising.

“It makes a lot of practical sense. Our brain physiology has been attuned to track dusk and dawn for millions of years,” stated Professor Foger.

“Then industrialization came along in an evolutionary blink, and we’re still trying to catch up.”

Participants in the healthcare study also provided saliva samples for DNA analysis, enabling researchers to include genetic factors in their evaluations.

Previous genetic studies have identified specific genes involved in how circadian clocks in various animals respond to seasonal changes.

Since humans share this gene, the authors could pinpoint a smaller group of interns with slight variations in their genetic makeup.

For this group, shift work was more disruptive due to the misalignment between seasonal circadian rhythms and their sleep schedules.

This leads to many questions, particularly regarding the health implications and how shift work affects different individuals.

However, these are questions researchers will seek to investigate further in the future.

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R. Kim et al. 2025. Seasonal timing and individual differences in shift work adaptation. npj digits. Pharmaceuticals 8, 300; doi:10.1038/s41746-025-01678-z

Source: www.sci.news

Even basic bacteria can forecast seasonal shifts

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Scanning electron microscope image Synechococcus Cyanobacteria

Eyes of Science/Science Photo Library

Despite being one of the simplest life forms on Earth, cyanobacteria are able to predict and prepare for seasonal changes based on the amount of light they receive.

It has been known for over a century that complex organisms can use day length as a cue to future environmental conditions – for example, days shortening before cold weather sets in. Phenomena such as plant and animal migration, flowering, hibernation and seasonal reproduction are all guided by such responses, known as photoperiodism, but this has not previously been seen in simpler life forms such as bacteria.

Luisa Jabbour Later, at Vanderbilt University in Nashville, Tennessee, colleagues artificially Synechococcus elongatus By exposing the cyanobacteria to different day lengths, they found that those that experienced simulated short days were two to three times better able to survive icy temperatures, preparing them for winter-like conditions.

By testing shorter and longer durations, the researchers found that it took four to six days for a response to appear.

Because these organisms can produce new generations within a matter of hours, their cells must pass on information about the length of daylight to their offspring, but researchers don’t yet understand how this information is transmitted.

Cyanobacteria, which capture energy from sunlight through photosynthesis, have been around for more than two billion years and are found almost everywhere on Earth.

“The fact that organisms as ancient and simple as cyanobacteria have a photoperiodic response suggests that this is a phenomenon that has evolved much longer than we had imagined,” says Jabbour, who is now at the John Innes Centre in Norwich, UK.

The team also looked at how gene expression patterns change in response to changes in day length, suggesting that photoperiodism likely evolved by exploiting existing mechanisms to cope with acute stresses such as bright light and extreme temperatures.

These findings also have implications for the evolution of circadian rhythms, the internal clocks that regulate day-night cycles, team members say. Karl Johnson At Vanderbilt University.

“I think we’ve always thought that circadian clocks evolved before organisms were able to measure the length of days and nights and predict the changing of seasons,” he says, “but the fact that photoperiodism evolved in such ancient, simple organisms, and that our gene expression results are linked to stress response pathways that seem to have evolved very early in life on Earth, suggests that photoperiodism may have evolved before the circadian clock,” Johnson says.

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Source: www.newscientist.com