Study helps identify children at the highest risk of severe RSV infection

A new study helps to identify children who are at the highest risk of a severe respiratory syncytial virus (RSV) infection and who would thus benefit most from new RSV prevention measures.

A registry study covering all Finnish and Swedish children and their family members identified 16 major risk factors for a severe RSV infection. The researchers created a clinical prediction model to predict the risk of hospitalisation from an RSV infection and showed that the model performed well in both countries.

This very large study on risk factors for a severe RSV infection, led by researchers from the University of Helsinki and Helsinki University Hospital, was recently published in the journal Lancet Digital Health.

The study confirmed that the risk for a severe RSV infection is highest at less than six months of age, and that the risk increases if the infant is born premature, has certain congenital conditions and young siblings. The new prognostic factors identified include oesophageal malformations and a less severe congenital heart disease.

In recent years, both a long-acting antibody that protects against an RSV infection and a vaccine given to mothers during pregnancy have been developed to prevent RSV infections. When targeted properly, such drugs can prevent a large number of complications in young children and decrease the number of hospital and intensive care stays, but it is not yet clear how widely these approaches should be used.

"It may not be possible to offer these new preventive measures to all children. Our research helps to identify the children who need them most, both at the individual level and in the population," says the lead author of the study, Pekka Vartiainen, a Postdoctoral Researcher from the Institute for Molecular Medicine Finland FIMM, University of Helsinki, and a MD specialising in paediatrics at HUS.

The disease burden of RSV infections is high

RSV is a common virus that causes respiratory infections, but it can be dangerous, especially for the infants. The disease burden of RSV epidemics is high all over the world. Globally, over 100.000 children die each year because of RSV infections.

RSV causes severe infections, especially in children under one year of age. In Finland, it is one of the most common causes of hospitalisation of young children and a major cause of infant mortality worldwide."

Santtu Heinonen, MD, Specialist in Paediatrics, from the HUS New Children's Hospital

In Finland, one in three children under one year of age is infected with RSV, and around 1000 of these children require hospital treatment for the RSV infection, significantly more than for influenza or coronavirus. In addition, otitis media is a common complication after an RSV infection.
The vast majority of patients acquire the infection during the few peak months of the epidemic. This places a significant burden on the health care system and often leads to the cancellation or postponement of procedures such as heart surgery.

The study combined several different registries

The research team utilised different national registries to investigate the factors that increase the risk of hospitalisation for RSV infections in children under one year of age. The study included 1.25 million children born in Finland between 1997 and 2020 and 1.4 million children born in Sweden between 2006 and 2020, and their parents and siblings. The simple 16-variable clinical prediction model created in the study performed equally well as did the 1,511-variable AI-based model.

For creating the prediction model, health data were harmonised and coded for AI use as part of the Finnish FinRegistry study. The resulting model was replicated in the corresponding Swedish registry data.

"In our study, we applied high-quality data and methodological expertise to solve a clinically important problem. The Nordic countries have exceptionally extensive and reliable registry data. There are few countries where such a study can be done," says Andrea Ganna, Associate Professor at the University of Helsinki, who led the study.

"This study is an example on how nationwide registry-based studies can help to target preventive efforts. The aim of the FinRegistry project is to produce scientific knowledge on risk factors and trajectories leading to various diseases, also those not observable with traditional methods," says Research Professor Markus Perola from the Finnish Institute for Health and Welfare (THL).

The study is a collaboration between clinicians at the HUS Centre for Paediatric Research, the Institute for Molecular Medicine Finland (FIMM) at the University of Helsinki, register researchers at the Finnish Institute for Health and Welfare (THL) and the Karolinska Institutet in Stockholm. The study is part of the FinRegistry research project, led by Research Professor Markus Perola from THL.

The predictive model developed in the study and the identified risk factors can be viewed at www.rsv-risk.org.