RSV Infection in Infancy Increases Childhood Asthma Risk

A prospective birth cohort research has revealed an age-dependent link between RSV infection in infancy and childhood asthma.

While a recent study found that respiratory syncytial virus (RSV) infection in the first year of life was linked to a higher risk of childhood asthma, the authors also highlight the finding that babies who were not exposed to RSV during this vulnerable time had a significant 26% lower risk of asthma at age 5.

Additionally, researchers from the Infant Susceptibility to Pulmonary Infections and Asthma Following RSV Exposure (INSPIRE) study discovered that 15% (95% CI 2.19-26.84) of current cases of asthma in people over the age of five may be avoided by avoiding RSV infection during infancy.

The researchers' findings were reported in a study that was published in The Lancet. "In this large, population-based birth cohort of healthy infants born at term, we showed that infants without RSV infection have a substantially reduced risk of developing childhood asthma compared with infants with RSV infection," the authors stated. "To our knowledge, INSPIRE is the first study specifically designed to test the hypothesis that avoiding RSV infection during infancy reduces the risk of childhood asthma," said the study's authors.

RSV infection during infancy and the beginning of asthma in children are related, although the link between RSV infection during infancy and the development of wheezing disorders in children is less evident.

In spite of the fact that researchers have regularly shown a connection between severe RSV and asthma over the last 60 years, the study demonstrated that this connection may also be partially explained by the fact that both severe RSV and asthma are heritable. The objective of the study was to determine the relationship between RSV and asthma by capturing all RSV infections using molecular techniques and postseason serology.

From 11 pediatric clinics in middle Tennessee, newborns with non-low birthweight who were delivered at term between June and December 2012 or between June and December 2013 were selected. Through both passive and active surveillance, Hartert and colleagues determined a baby's RSV infection status during the first year of life. In addition to routine parental interaction, some medical appointments included blood tests and nose cleanses for newborns.

All patients who successfully completed the 5-year follow-up were prospectively tracked for the main outcome of 5-year current asthma, which researchers assessed. The study's secondary outcomes were recurrent wheezing and a 5-year current inflammatory subtype of asthma.

In all, 1946 kids (48% females; median age, 55 days) were recruited in INSPIRE, and 1741 of them (89%) had data that could be used to determine whether or not they had RSV infection in their first year of life. 54% (n=944) of the 1741 individuals with accessible RSV infection data had contracted the illness while still infants.

Researchers found that fewer kids (91 [16%] of 587) without RSV infection during infancy than those with RSV infection during infancy (139 [21%] of 670; p=0.016) had 5-year current asthma.

When compared to participants who contracted RSV during infancy, those who did not had a 26% lower risk of developing asthma today in five years (adjusted rate ratio [aRR] 0.74, 95% CI 0.58-0.94; P=.014).

The percentage of children with recurrent wheeze was lower among those who did not have RSV during infancy than it was among those who did. In addition, fewer babies without RSV infection developed 5-year current nonatopic asthma than participants with RSV infection during infancy; however, "this finding was not significant for 5-year current atopic asthma," concluded Hartert et al.

It is crucial to understand that while our results point to a causal relationship, the observational methodology of our research prevents us from conclusively proving causation. The necessity for long-term monitoring of common respiratory outcomes in children taking part in existing and upcoming clinical studies of RSV immunoprophylaxis drugs is instead highlighted by our findings.

The lack of relevance to people outside the study group as well as the possibility of RSV misclassification in certain cases, where babies who actually have RSV were not formally identified, were also highlighted by researchers.

Reference:

Hartert TV, Rosas-Salazar C, Chirkova T, et al. Respiratory syncytial virus infection during infancy and asthma during childhood in the USA (INSPIRE): A population-based, prospective birth cohort study. Lancet. Published online April 19, 2023. doi:10.1016/S0140-6736(23)00811-5.