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. 2018 Oct 31;13(10):e0205399.
doi: 10.1371/journal.pone.0205399. eCollection 2018.

Population-based trends and underlying risk factors for infant respiratory syncytial virus and bronchiolitis hospitalizations

Mihoko V Bennett  1   2 , Kimmie McLaurin  3 , Christopher Ambrose  3 , Henry C Lee  1   2
Affiliations

Population-based trends and underlying risk factors for infant respiratory syncytial virus and bronchiolitis hospitalizations

Mihoko V Bennett et al. PLoS One. .

Abstract

Objective: Respiratory syncytial virus (RSV) is a common pathogen during infancy, with the potential to cause serious disease and mortality in high-risk groups. The objective of this study was to characterize trends of RSV and bronchiolitis hospitalizations in the first year in a population-based cohort and assess differences in trends according to risk status.

Methods: Using an observational retrospective cohort design, we examined a California population-based dataset of vital statistics linked to hospital discharge data for up to 1 year after birth from 1997-2011. Infants were categorized by medical condition and then by gestational age. Medical conditions of interest included chronic lung disease, certain congenital heart diseases, or others known to affect risk for developing severe bronchiolitis. The primary outcome was hospitalization due to RSV; secondary outcome was hospitalization for unspecified bronchiolitis (UB) not coded as RSV. Annual person-year rates were calculated for infants <12 months of age during January to December of each year.

Results: Of 7,298,401 infants born during the study period, 121,230 (1.7%) had a medical condition associated with risk; these infants experienced 6853 RSV and 6568 UB hospitalizations in the first year. In infants without medical conditions, 96,694 RSV and 69,886 UB hospitalizations occurred. All-cause infant hospitalizations declined over time from 12.2 to 9.3 per 100 person-years. RSV hospitalization rates for infants with medical conditions decreased from 7.6 to 3.4 per 100 person-years, with the largest relative decline in infants with chronic lung disease (12.0 to 5.0 per 100 person-years). For infants without medical conditions, RSV hospitalizations declined from 1.4 to 0.8 per 100 person-years, with greater decreases among preterm infants with earlier gestational age. UB hospitalization rates remained relatively stable across the study years, from 6.2 to 5.4 and 1.0 to 0.8 per 100 person-years for infants with and without medical conditions.

Conclusions: Various interventions may have contributed to observed decreases in RSV hospitalizations from 1998-2011, which were greater in high-risk populations recommended for RSV immunoprophylaxis and not observed with UB. Further efforts to promote evidence-based practice and optimal targeting of appropriate interventions will ensure continued improvement in care for vulnerable infants.

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Conflict of interest statement

This study was supported by AstraZeneca (Gaithersburg, MD). KM and CSA are employed by AstraZeneca. HL received funding from AstraZeneca for research effort and travel expenses to present findings at a national conference. MB received research funding from AstraZeneca. There are no patents, products in development, or marketed products to declare. This does not alter our adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Figures

Fig 1
Fig 1. Patient cohort.
Fig 2
Fig 2. Rates by identified medical condition.
(A) Rates of RSV and UB by identified medical condition status. (B) Rates of RSV by identified medical condition. (C) Rates of UB by identified medical condition. CHD, congenital heart disease; CLD, chronic lung disease; RSV, respiratory syncytial virus; UB, unspecified bronchiolitis.
Fig 3
Fig 3. Rates of hospitalization by GA in infants without medical conditions.
(A) Rates of RSV by GA in infants without a medical condition. (B) Rates of UB by GA in infants without medical a condition. GA, gestational age; RSV, respiratory syncytial virus; UB, unspecified bronchiolitis.
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Publication types

Grants and funding

This study was supported by AstraZeneca (Gaithersburg, MD). HL received funding from AstraZeneca for research effort and travel expenses to present findings at a national conference. MB received research funding from AstraZeneca. AstraZeneca provided support in the form of salaries for authors KM and CA, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section. Editorial support was provided by The Lockwood Group, which was in accordance with Good Publication Practice (GPP3) and funded by AstraZeneca.