Scientists from the Flanders Institute for Biotechnology (VIB) and Ghent University (UGent), in collaboration with researchers in Denmark, have reported strong new evidence that severe respiratory syncytial virus (RSV) infections in early infancy significantly increase the risk of developing childhood asthma. The findings, published in Science Immunology, highlight a critical early-life window during which respiratory and immune development may be especially vulnerable, particularly in children with a family history of asthma or allergies.
Childhood asthma remains a major global health concern. In 2019, it accounted for an estimated 22 million new cases worldwide and resulted in about 5.1 million disability-adjusted life years, underscoring its profound impact on health, quality of life, and long-term development. While asthma prevention has been a longstanding public health priority, the new study provides some of the clearest evidence to date that early viral infections may play an active role in shaping lifelong respiratory outcomes.
The research team combined population-wide Danish health registry data with controlled laboratory experiments to investigate the link between severe RSV infection and later allergic disease. Their analysis revealed a strong interaction between an infant’s inherited allergy risk and the effects of early RSV illness. Infants who experienced severe RSV in the first months of life were more likely to develop increased immune responses to common allergens such as house dust mites. The risk was further amplified in children with allergic or asthmatic parents, as allergen-specific antibodies transferred from mother to child increased susceptibility.
The study also showed that protecting newborns from RSV prevented these harmful immune changes and reduced the likelihood of developing asthma in experimental models. According to the researchers, the expanding availability of RSV prevention options presents an important opportunity to improve long-term respiratory health, with benefits extending beyond the reduction of hospitalizations.
Preventive measures such as maternal RSV vaccination during the third trimester and long-acting antibody injections for newborns are being introduced in several countries, though uptake remains inconsistent. Experts caution that if RSV prevention also lowers the risk of childhood asthma, the potential public health impact could be transformative.
Another well-known study by Sigurs and colleagues further supports the connection between severe early RSV infection and later asthma. The study found that infants hospitalized with RSV bronchiolitis were significantly more likely to develop asthma and allergic sensitization by age seven and a half compared with matched controls. Their findings identified RSV bronchiolitis as the strongest independent predictor of later asthma, suggesting that severe early-life infections do more than reveal an underlying predisposition, they may actively shape immune pathways linked to asthma and allergy.
The accumulating evidence indicates that RSV infection in the earliest months of life is not merely an acute respiratory illness but a potential driver of long-term immune changes that increase the likelihood of childhood asthma. With the introduction of maternal RSV vaccination and long-acting monoclonal antibodies for newborns, there is now an opportunity to intervene during this sensitive developmental period. Broader and equitable uptake of these preventive options could offer benefits beyond reducing infant hospitalizations. By limiting early RSV infections, public health systems may help lower the lifetime respiratory disease burden, ultimately reducing the global impact of childhood asthma on families, communities, and healthcare resources.
Reference
- De Leeuw E, Justesen JF, Bosteels C, Debeuf N, Vanheerswynghels M, Jonckheere L, et al. Maternal allergy and neonatal RSV infection synergize via FcR-mediated allergen uptake to promote the development of asthma in early life. Science Immunology. 2025 Nov 28;10(113):eadz4626.
- Sigurs N, Bjarnason R, Sigurbergsson F, Kjellman B. Respiratory Syncytial Virus Bronchiolitis in Infancy Is an Important Risk Factor for Asthma and Allergy at Age 7. Am J Respir Crit Care Med. 2000 May;161(5):1501–7.