Scientists at Pompeu Fabra University discovered that mice recovering from an acute viral infection experienced prolonged problems with their immune defenses. Although the animals had successfully fought off the virus, their immune systems remained impaired, making it harder to respond to new threats. Remarkably, mice vaccinated before infection did not develop these problems, suggesting that vaccination may provide an additional layer of protection beyond preventing illness.

Most people think of common viral infections, such as colds or stomach viruses, as temporary illnesses. A virus enters the body, multiplies, causes symptoms, and is eventually brought under control by the immune system. Once symptoms disappear, recovery is generally considered complete. The immune response also creates protection against future encounters with the same virus.

But what if the immune system continues to experience harmful effects long after the infection appears to be over?

Viral Infections Can Leave Lasting Immune Damage

Researchers from Pompeu Fabra University’s Infection Biology Laboratory investigated this possibility in a study published in Cell Death & Disease.

Using mice with acute viral infections, the team examined what happened to their immune systems after the animals had recovered. They found that eliminating the virus did not necessarily restore normal immune function. Instead, the infection left behind changes that persisted well beyond the initial illness.

According to Andreas Meyerhans, an ICREA research professor at UPF, who led the research, “there is a general perception that an acute viral infection is a relatively minor and transient event: once the virus is controlled and the symptoms have resolved, the body has fully recovered and is back to normal. But this view may underestimate consequences that are not immediately visible and can persist long after the infection itself has resolved.”

The researchers traced these lingering effects to significant changes in the spleen, an organ that plays an important role in coordinating immune defenses. As the immune system fought to eliminate the virus, the spleen developed fibrosis, a condition involving the buildup of scar-like tissue. The arrangement and positioning of immune cells within the organ also became disrupted.

These structural changes interfered with the interactions between immune cells that are necessary to activate T cells. These specialized cells are essential to adaptive immunity because they help recognize and destroy infected cells.

As a result, the mice remained less capable of launching effective immune responses when exposed to new challenges. Even though the original infection had been brought under control, their immune defenses continued to function poorly.

“The infection can be controlled, but that does not necessarily mean that the host has fully recovered,” says Dr. Paula Cebollada Rica, first author of the study. “Our findings show that the immune-related consequences of an acute viral infection can persist beyond the period in which the virus is detectable, leaving the animals in an immunocompromised state.”

Vaccination Prevented Lasting Immune System Damage

After identifying these long-term effects, the scientists investigated whether they could be avoided. They focused on vaccination, which prepares the immune system to recognize and fight a pathogen before an infection occurs.

The results revealed a striking difference between vaccinated and unvaccinated animals. Mice that received vaccination before infection did not develop the spleen damage or immune dysfunction seen in the other group.

Their spleens maintained their normal structure, and their T cells continued to function at levels comparable to those of mice that had never been infected.

This finding suggests that vaccination can protect the immune system itself from some of the harmful consequences of fighting a viral infection. In the mouse model, vaccination not only protected against the disease caused by the virus but also preserved the animals’ ability to respond to future immune challenges.

“Vaccinated animals did not experience T-cell dysfunction or splenic alterations after recovering from an acute viral infection. This means that vaccination not only prevented the disease resulting from the acute infection but also preserved the immune system’s ability to cope with new challenges,” Cebollada Rica explains.

A Hidden Benefit of Vaccines With Public Health Implications

The findings broaden the potential benefits of vaccination by highlighting a form of protection that may not be immediately apparent. Beyond reducing the immediate effects of an infection, vaccines may also help prevent persistent changes that weaken immune defenses.

Although these results were obtained in mice and do not establish that the same effects occur in humans, they raise important questions about how viral infections influence long-term immune health and how vaccination might help protect it.

The research also comes at a time when vaccination policies and infectious disease prevention efforts are increasingly influenced by political decisions. The researchers emphasize the importance of scientific evidence in understanding the full consequences of infections, particularly when policy choices can undermine coordinated efforts to prevent infectious diseases.

Understanding the broader benefits of vaccination could therefore influence not only medical care but also how public health officials explain the value of vaccines to the public.

“The benefits of vaccination highlighted by this research are important not only for healthcare, but also for how we communicate the value of vaccination to the population at large,” Meyerhans states. “It is important that people are aware of the broader protection that vaccination can provide and continue to trust in vaccines as one of the most effective tools to prevent diseases. Put simply, vaccines provide strong health benefits at a relatively low cost to society.”

The independent, preliminary research was presented at the American Heart Association’s Scientific Sessions 2026, held November 6 through 9 in Chicago. The annual conference brings together cardiovascular researchers and healthcare professionals from around the world to share scientific discoveries, emerging evidence, and advances in clinical care.

An estimated 25% of American adults have elevated levels of low-density lipoprotein-cholesterol (LDL-C), commonly called “bad cholesterol.” When too much LDL cholesterol accumulates in the arteries, it can restrict blood flow and contribute to heart attacks and strokes. Statins are widely prescribed to lower cholesterol and reduce these risks, including in people who have never experienced a cardiovascular event. This preventive approach remains a central part of the American Heart Association’s 2026 joint guideline on dyslipidemia.

Do Older Adults Need to Keep Taking Statins?

Although statins are an established treatment for reducing cardiovascular risk, questions remain about how much benefit they provide when people reach their 70s and beyond, particularly if they have never had a heart attack or stroke.

“While the Association’s recent joint guideline recommends lifestyle and potentially medication for people with high LDL-C at younger ages to reduce the risk of heart attack and stroke, recent studies question the health benefits of continuing statins in the later decades of life,” said study author Rita F. Redberg, M.D., M.Sc., FAHA, professor of cardiology and the Araxe Vilensky Endowed Chair in Cardiology at the University of California, San Francisco School of Medicine. “A few previous studies assessed the safety of discontinuing statins for primary prevention at age 70 and later, and they found no difference in mortality. One study suggested quality of life improvements after stopping statins. Whether it is safe to discontinue statins to prevent a first CVD event in the elderly remained unclear and the question we explored in our study.”

To investigate, researchers enrolled nearly 1,900 adults aged 70 and older who were taking statins specifically to prevent a first cardiovascular event. Every participant also had at least two chronic medical conditions, such as a history of cancer or lung disease.

Participants were divided into two groups. One group stopped taking statins, while the other continued their prescribed treatment. Researchers tracked their health for approximately two years, with additional follow-up extending as long as four years. They examined rates of heart attack, stroke, and death, along with changes in quality of life, muscle pain, falls, and muscle wasting (known as sarcopenia).

What Happened When Older Adults Stopped Statins?

The initial findings were largely reassuring. After approximately two years, participants who stopped taking statins did not experience a statistically significant increase in heart attacks, strokes, or deaths compared with those who remained on the medications.

Stopping treatment also did not produce measurable improvements in the other outcomes researchers examined. Quality of life, muscle discomfort, falls, and muscle wasting were similar in both groups.

There was, however, a small difference in cardiovascular outcomes. Over the first two years, the results indicated approximately one additional cardiovascular event for every 40 people who discontinued statins compared with those who continued treatment.

The longer follow-up revealed a more concerning pattern. Over a period of up to four years, 12.7% of participants who stopped statins experienced a heart attack, stroke, or death, compared with 9.2% of those who kept taking the medications.

Longer Follow-Up Reveals a Potential Risk

Redberg explained that the higher rate of serious outcomes during the four-year follow-up represents a new finding in research on statin discontinuation among older adults. She suggested that the difference may have emerged because this trial included more participants and tracked them for a longer period than earlier studies.

These results complicate the question of whether older adults should continue cholesterol treatment indefinitely. While the findings suggest that stopping statins may be a reasonable option for many people in this age group, they also indicate that remaining on treatment could offer some protection over time.

“This small, increased risk of cardiovascular events means that one cannot make a general recommendation about stopping statins in this patient population,” she said. “There should be shared decision-making between the patient and the healthcare professional to know if it is appropriate for an individual to discontinue the medication. In general, however, discontinuation is safe for most people who are in this age group and without a previous CVD event.”

Study Design and Important Limitations

The trial involved 1,880 participants aged 70 and older (average age of 77; 53% men, and 47% women), all of whom had at least two chronic health conditions. Individuals with established cardiovascular disease or a previous cardiovascular event were not eligible to participate.

Researchers conducted the study between November 2021 and April 2026 across 24 medical centers in Switzerland, France, and the Netherlands. Of the participants, 938 were assigned to discontinue statins, while 942 were assigned to continue taking their medications.

Throughout the trial and subsequent follow-up, researchers recorded heart attacks, acute ischemic strokes, and deaths from any cause. Participants also completed surveys assessing their overall quality of life, muscle pain, falls, and sarcopenia.

One limitation was that some participants did not remain in their originally assigned groups. Some people instructed to stop statins eventually resumed treatment, while others assigned to continue taking statins stopped using them. Altogether, approximately 14% of participants switched from their assigned treatment approach during the study.

To determine whether these changes affected the findings, the researchers performed several additional statistical analyses. The results remained unchanged.

Taken together, the findings suggest that discontinuing statins may be an option for many adults over 70 who have not previously experienced cardiovascular disease, especially when considering outcomes over the first two years. However, the higher rate of heart attacks, strokes, and deaths during longer follow-up underscores why stopping treatment should be an individualized decision made with a healthcare professional rather than a general recommendation for all older adults.

An international research team led by The University of Manchester investigated volcanic material from the 2021 Tajogaite eruption on La Palma, Spain. Their findings reveal that a process known as “superheating” can dramatically slow the formation of crystals inside magma as it travels upward toward Earth’s surface.

Superheating occurs when magma reaches temperatures above those at which its crystals would normally remain stable. The researchers found that this extra heat can keep magma relatively fluid for much longer than expected, potentially allowing it to rise rapidly and produce spectacular lava fountains.

The discovery, published in Nature Communications, offers new insight into a long-standing question in volcanology: How does magma’s temperature history influence the way a volcano erupts?

How Extreme Heat Changes Magma Deep Inside Volcanoes

Magma is a mixture of molten rock, gases, and sometimes solid crystals beneath Earth’s surface. Once it emerges from a volcano, it is called lava. Although temperature and chemical composition are important in determining how magma behaves, the new research suggests that the heating it experienced before an eruption can also make a major difference.

Under normal conditions, crystals begin forming as magma cools. This process often starts around tiny existing crystals that act as “seeds,” providing surfaces on which additional crystals can grow.

Superheating can disrupt this process in two important ways. First, sufficiently high temperatures can dissolve the microscopic crystal seeds that would otherwise encourage new crystals to develop. Second, the heat changes the internal structure of the molten material, making it more uniform and less favorable for new crystal formation.

These changes matter because crystals affect magma’s viscosity, which describes how easily a substance flows. As more crystals develop, magma generally becomes thicker and more resistant to movement. This can influence both its speed of ascent and the way trapped volcanic gases escape.

Lead author Dr. Barbara Bonechi, Research Associate at The University of Manchester, explained:

“The history of crystal and bubble growth can dramatically control how a magma erupts, in particular as more crystals grow, they eventually have a dramatic effect on magma viscosity. Until now, we did not fully understand the dynamics of crystal growth for magmas that received an injection of superheat just before ascent. But using our exciting and newly developed X-ray transparent pressure vessel combined with synchrotron X-ray microtomography, we can actually observe these processes ‘in situ’.”

Scientists Discover an Eight-Hour Delay in Crystal Formation

To investigate what happens inside superheated magma, the researchers recreated volcanic conditions in the laboratory using material collected from the Tajogaite eruption. The magma involved in that eruption may have experienced superheating before reaching the surface and while rising through Earth’s crust.

The team conducted experiments under carefully controlled temperatures and pressures designed to reproduce conditions encountered by magma underground.

At Diamond Light Source, a major scientific research facility, the researchers used synchrotron X-ray microtomography to watch crystals develop in real time. This advanced imaging technique uses extremely powerful X-rays to examine the internal structure of materials in three dimensions without having to cut them open.

A specially developed pressure vessel that allows X-rays to pass through it made these observations possible while the magma was subjected to volcanic conditions.

The team also performed complementary experiments in Prague, where samples could be examined over longer periods outside the real-time imaging setup. Together, these approaches allowed the researchers to observe how different heating conditions affected the timing of crystal formation.

The results revealed a remarkable difference.

Magma that had not undergone superheating began producing crystals after approximately 20 minutes. However, when magma was subjected to strong superheating, the beginning of crystallization was delayed for more than eight hours.

This substantial delay suggests that intense heating can leave magma without newly forming crystals for far longer than scientists might otherwise expect, with potentially important consequences for volcanic eruptions.

Why Superheated Magma Could Produce Towering Lava Fountains

The researchers next explored how these laboratory findings might affect real volcanoes.

They incorporated the measured delays in crystal formation into computer models that simulate how magma rises through Earth’s crust. These models account for changes in magma properties as the molten material moves toward the surface.

The simulations revealed two very different possibilities.

When superheating delays crystallization, magma can remain relatively fluid as it rises. Because it encounters less resistance to flowing, it may travel upward more rapidly, potentially creating conditions that favor dramatic lava fountains.

These spectacular eruptions occur when escaping volcanic gases propel molten rock high above a vent, producing jets and fountains of glowing lava.

In contrast, magma that begins crystallizing earlier becomes more viscous and tends to ascend more slowly. This slower movement gives volcanic gases additional time to escape, favoring gentler eruptions in which lava flows out onto the surface rather than being thrown high into the air.

Such behavior is known as an effusive eruption, a type of volcanic activity characterized primarily by flowing lava.

The findings suggest that even when volcanic systems have similar characteristics, differences in their earlier heating histories may help explain why their eruptions look and behave so differently.

A New Clue for Predicting Volcanic Eruptions

Understanding what happens to magma before it reaches the surface is essential for assessing volcanic hazards. Scientists monitor signals such as earthquakes, ground deformation, and volcanic gas emissions to identify changes within active volcanoes.

However, predicting exactly how an eruption will unfold remains difficult. Two volcanoes with seemingly similar magma compositions and gas conditions can still display markedly different eruptive behavior.

The new research suggests that the effects of superheating and the timing of crystal formation deserve greater attention in volcanic forecasting models.

By accounting for these previously underappreciated processes, researchers may eventually be able to better interpret volcanic monitoring data and assess whether rising magma is more likely to produce vigorous lava fountains or gentler lava flows.

The results do not mean that magma temperature alone determines how explosive an eruption will be. Instead, they identify another important piece of the complex physical processes that shape volcanic activity.

Co-author Dr. Margherita Polacci, Senior Lecturer in Volcanology at The University of Manchester, highlighted the potential importance of the findings for understanding volcanic hazards:

“Current volcanic hazard models typically focus on magma chemistry, gas content and pressure changes. This work suggests that pre-eruptive thermal history and crystallization kinetics may also play an important role in controlling magma ascent and eruptive behavior, with implications for volcanic hazard assessment.”