Vaccination protected mice from lasting immune damage after viral infection

Researchers at the Infection Biology Laboratory of Pompeu Fabra University (UPF) have found that mice that overcome an acute viral infection can be left with a weakened immune system even after the virus is gone. Animals vaccinated before infection did not develop these problems. The results, published in the journal Cell Death & Disease, point to a possible additional benefit of vaccines, but they come from an animal model and do not establish that the same happens in people.

What the study found

Common viral illnesses such as colds or stomach bugs are usually treated as temporary: once symptoms fade, recovery is considered complete. The scientists tested whether the immune system really returns to normal. They found that clearing the virus did not necessarily restore normal immune function.

The effects were traced to changes in the spleen, an organ that helps coordinate immune defenses. While the body fought the virus, the spleen developed fibrosis, a build-up of scar-like tissue, and the arrangement of immune cells inside it was disrupted. This interfered with the cell interactions needed to activate T cells, which are essential to adaptive immunity because they help recognize and destroy infected cells. As a result, the mice were less able to mount effective responses to new threats.

Study leader Andreas Meyerhans, an ICREA research professor at UPF, says an acute viral infection is often seen as minor and transient, a view that may underestimate consequences that are not immediately visible. First author Dr. Paula Cebollada Rica stresses that an infection can be controlled without the host having fully recovered.

The effect of vaccination

Mice vaccinated before infection did not develop spleen damage or immune dysfunction. Their spleens kept a normal structure, and their T cells worked at levels comparable to those of mice never infected. According to the researchers, vaccination not only prevented the disease but also preserved the immune system's ability to cope with new challenges.

Public health implications

The researchers note that vaccination policy and infectious disease prevention are increasingly shaped by political decisions, and they stress the importance of scientific evidence. Meyerhans says people should be aware of the broader protection vaccines can provide, adding that vaccines deliver strong health benefits at a relatively low cost to society.