When Are Infants Most Vulnerable to Asthma?

Infants who contract severe respiratory syncytial viral (RSV) disease after the age of 6 months are twice as likely to develop severe asthma in later years, says a new study. 

These authors believe this new study should inform how to implement the immunization against RSV to boost immunity beyond the reach of the maternal vaccine. 

This study was the 1st to examine at what age an infant is most vulnerable to developing asthma, after a severe bout of RSV. 

This news is important since almost all children will be infected with RSV by their 2nd birthday, says the Centers for Disease Control and Prevention (CDC).   

RSV is the most common cause of bronchiolitis and pneumonia in children younger than 1 year of age in the United States. 

Approximately 57,000 children younger than 5 years old are hospitalized due to RSV infection each year.

This new study of hospitalized babies due to RSV over a 10-year period was published in the Journal of Infectious Diseases, on December 4, 2018. 

RSV is the leading cause of lower respiratory tract infections like bronchiolitis in infants. 

Moreover, early RSV disease is also a strong predictor of future childhood asthma. 

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Dr. Nusrat Homaira, from the School of Women’s & Children’s Health, at the University of New South Wales, said in a press release, ‘the research has important implications for the development and implementation of a promising vaccine.’ 

“In the last 10 years, there has been unprecedented development of a vaccine for RSV because it's such a huge problem.” 

Dr. Homaira said “80 percent of infants get the RSV disease by their 2nd birthday.’   

“The vaccine under development is going to be given to women during their third trimester to boost the maternal antibodies, which will protect babies against severe RSV.”

However, Dr. Homaira says ‘protection from a ‘passive’ vaccine administered to an expectant mother may only protect as far as 6 months into the baby’s life following birth.’ 

‘After this time, an infant could still develop an RSV infection.’ 

Dr. Homaira and her co-authors looked at 18,042 children with severe RSV disease who were hospitalized in their first 2 years of life in NSW between 2001 and 2010 and saw two interesting patterns emerge. 

First, 60 percent of all hospital admissions were for infants aged 6 months or younger. 

“This confirmed that there is a very good reason to develop the maternal vaccine because it is going to protect them in the first six months of their life,” Dr. Homaira says. 

But, the 2nd finding was one that surprised the research team. 

Contrasted with the study cohort of infants who contracted RSV in their first six months of life, the 40 percent of children hospitalized after the age of 6 months more went on to return to the hospital with severe asthma in later years. 

“So what our analysis showed is that even though there are more severe RSV cases in the first 6 months of life, if severe RSV is after 6 months of age, the rate of subsequent asthma is actually higher in those children.” 

“While the maternal vaccine is extremely important for our children, we also need an active vaccination strategy or an active vaccine candidate that is going to protect children in the first 2 years of life,” Dr. Homaira says. 

Recent RSV vaccine news: 

• RSV Vaccine Clinical Trial Launched by Cincinnati Children’s Hospital
• RSV Vaccine Candidate Intends to Increase Neutralizing Antibody Levels in Pregnant Women
• RSV Phase 3 Study Reaches Enrollment Milestone

In a previous study, Dr. Homaira looked at the rate of asthma in children who had been hospitalized from RSV in their first two years and those who hadn’t. That study concluded that the first group was twice as likely to develop asthma than those children who hadn’t had severe RSV. 

“This is a novel study, there is nothing published in this space which has looked at this specific analysis.” 

“So one of our conclusions in the paper is there is a need for further study in other settings to validate what we have found out,” said Dr. Homaira.