RSV prevention in infancy has minimal impact on asthma in early childhood
Prophylaxis for respiratory syncytial virus (RSV) infection in healthy preterm infants reduced their risk of parent-reported (but not physician-diagnosed) asthma at age 6 years, with no apparent effect on lung function, according to follow-up results of the MAKI* study.
“RSV prevention did not have a major effect on current asthma or lung function … [and] only reduced the risk of parent-reported infrequent wheeze at age 6 years, while the risk of physician-diagnosed asthma did not decrease,” said the researchers.
“Future RSV vaccine studies will inform on whether RSV prevention is related to the risk of asthma at school age in the general population,” they said.
Between 2008 and 2010, 429 healthy infants born at 32–35 weeks of gestation were randomized to receive either prophylactic palivizumab (n=214) or placebo (n=215) during the RSV season in their first year of life. Of these, 92 percent (n=395) completed the 6-year, assessor-blind, follow-up study which examined the effect of RSV prevention during infancy on asthma and lung function at age 6 years.
For parent-reported asthma, the trial participants’ parents completed questionnaires on their children’s respiratory health at age 3 and 6 years, while information on current physician-diagnosed asthma was obtained from general practitioners treating the children.
There was a numerically lower incidence of parent-reported current asthma (defined as a composite of wheeze and use of asthma medication in the last 12 months) in children who had received palivizumab compared with those who received placebo (14.1 percent [n=28] vs 24.0 percent [n=47], absolute risk reduction [ARR], 9.9 percent, 95 percent confidence interval [CI], 2.2–17.6 percent). [Lancet Respir Med 2018;6:257-264]
This difference was primarily due to the lower incidence of infrequent wheeze (one to three episodes in the previous year) among patients previously assigned to palivizumab compared with placebo (6.0 percent vs 13.4 percent, ARR, 7.4 percent).
Forced expiratory volume in 0.5 seconds (FEV0.5) was comparable between children who had received palivizumab and placebo (89.1 percent vs 90.1 percent).
A post-hoc analyses demonstrated similar incidence of physician-diagnosed asthma in the last 12 months between children who had received palivizumab and placebo (10.3 percent vs 9.9 percent, ARR, -0.4 percent, 95 percent CI, -6.5 to 5.8 percent).
“[T]his has led us to conclude that RSV prevention does not reduce clinically relevant asthma symptoms at age 6 years,” said the researchers.
One reason postulated by the researchers for the difference in parent-reported and physician-diagnosed asthma was that the asthma symptoms experienced by the children may not have been serious enough to require a physician consultation. The potential for bias was also not excluded as parents were aware of treatment allocation during the follow-up period.
The researchers pointed out that the study population comprised healthy preterm infants and as such, the results may not extend to term infants. In addition, the impact of RSV prevention on various asthma phenotypes was not determined, and lung function was assessed when the children did not have respiratory symptoms which may have led to an overestimation of lung function.