Pneumococcal colonization rate lower in children with persistent asthma

Children with persistent asthma are less likely to be colonized with S. pneumoniae than those without asthma when seeking care for respiratory symptoms, reports a study. 

This finding remains true even after adjusting for factors that can influence pneumococcal colonization like immunization status, antibiotic use, and smoking exposure.

“More children with persistent asthma receiving ≥3 doses of PCV7 and/or PCV13 than children without asthma could have contributed to the lower pneumococcal colonization rate in asthmatics,” the researchers said. 

In this study, nasal mid-turbinate samples were collected per routine care from children aged 5 to 18 years with upper respiratory symptoms from November to April (respiratory seasons) of 2017 to 2018 and 2018 to 2019 in Kansas City, US.

Researchers then obtained pneumococcal immunization status, prior antibiotic use, and other clinical data. They also tested samples for pneumococcal colonization by real-time polymerase chain reaction (PCR) targeting lytA gene. Positive samples went through multiplex serotype-specific PCR assays to determine the serotype.

A total of 363 children (87.6 percent were aged 5 to 10 years, 50.1 percent were female, and 74.1 percent received ≥3 doses of a pneumococcal conjugate vaccine) were included, of whom 120 had persistent asthma and 243 had no asthma. [Pediatr Infec Dis J 2024;43:1033-1039]

Children with persistent asthma had lower pneumococcal colonization rate than those without asthma (10 percent vs 18.9 percent; p=0.03). After adjusting for demographic and clinical data, the likelihood of colonization remained lower in asthmatic kids (odds ratio, 0.4, 95 percent confidence interval, 0.2–0.9).

Of the positive samples obtained, 77.6 percent had confirmed pneumococcal serotype, with 35.6 percent corresponding to PCV13 serotype and 64.4 percent to non-PCV13 serotypes. The most common serotypes were 19F (15 percent), followed by 3 (13 percent) and 6C/6D (11 percent).

“Pneumococcal serotype distribution did not differ between the persistent asthma and nonasthma group,” the researchers said. “Larger prospective studies are needed to further understand the complex dynamics of pneumococcal colonization in children with asthma and its subsequent risk for invasive pneumococcal disease (IPD).”

PCV

The current study had a higher proportion of children with persistent asthma receiving ≥3 doses of PCV7 or PCV13 than those without asthma, and this difference could have influenced the lower colonization rate in the asthmatic group.

"PCV has been shown to not only reduce IPD incidence but also decrease the nasopharyngeal colonization rates of vaccine serotypes,” the researchers said. [J Infect Dis 2007;196:1211-1220; Pediatrics 2017;140:e20170001]

“The Experimental Human Pneumococcal Challenge model study suggested that the main protective mechanism of PCV13 against colonization is the reduction of S. pneumoniae colony density; however, some observational studies have not found a difference in colonization density in vaccinated versus unvaccinated groups,” they added. [Vaccine 2019;37:3953-3956; Vaccine 2017;35:945-950]

Asthma is the most common chronic medical condition in children, with a prevalence of 11 percent to 13 percent across the globe and 6 percent to 9 percent in the US. [Int J Tuberc Lung Dis 2014;18:1269–1278; https://www.cdc.gov/asthma/most_recent_data.htm]