The Role of Attributable Fraction in the Exposed in Assessing the Association of Microorganisms With Pneumonia

The role of birth month in the burden of hospitalisations for acute lower respiratory infections due to respiratory syncytial virus in young children in Croatia

Background

Birth month was an important risk factor for respiratory syncytial virus (RSV) hospitalisation in infants. However, little is known about the role of birth month in RSV hospitalisation in finer age bands during infancy, which is relevant to strategies for RSV passive immunisations for infants. We aimed to understand the role of birth month in the burden of RSV-associated acute lower respiratory infection (ALRI) hospitalisation in finer age bands of the first year of life.

Methods

In this retrospective study, we analysed the hospitalisation records during 2014–19 at the University Hospital of Split, Split-Dalmatia County, Croatia. We estimated all-cause and RSV associated ALRI hospitalisation rates among children under five years, with a focus on infants by finer age band and birth month.

Results

We included 1897 ALRI hospitalisations during the study period. Overall in children under five years, annual hospitalisation rate was 14.66/1000 (95% CI: 14.01–15.34) for all-cause ALRI, and was 7.56/1000 (95% CI: 6.83–8.34) for RSV-ALRI. RSV-ALRI hospitalisation rate was highest in infants aged 28 days–<3 months (61.15/1000, 95% CI: 52.91–70.31). Infants born in November, December and January (2–3 months before RSV peak) had the highest hospitalisation rates during infancy. Depending on the birth month of infants, the risk of RSV-ALRI hospitalisation peaked at different months of age; infants who were born in September had the highest RSV-ALRI hospitalisation rate at the age of 3–<6 months.

Conclusions

Our study underlines the importance of birth month in planning RSV immunisation strategies for infants, and provides useful baseline data for effectiveness analysis of novel RSV prophylactic products.

The role of viral co-infections in the severity of acute respiratory infections among children infected with respiratory syncytial virus (RSV): A systematic review and meta-analysis

Background

Respiratory syncytial virus (RSV) is the predominant viral cause of childhood pneumonia. Little is known about the role of viral-coinfections in the clinical severity in children infected with RSV.

Methods

We conducted a systematic literature review of publications comparing the clinical severity between RSV mono-infection and RSV co-infection with other viruses in children under five years (<5y). Clinical severity was measured using the following six clinical outcomes: hospitalisation, length of hospital stay, use of supplemental oxygen, intensive care unit (ICU) admission, mechanical ventilation and deaths. We summarised the findings by clinical outcome and conducted random-effect meta-analyses, where applicable, to quantitatively synthesize the association between RSV mono-infection/RSV co-infection and the clinical severity.

Results

Overall, no differences in the clinical severity were found between RSV mono-infection and RSV co-infection with any viruses, except for the RSV-human metapneumovirus (hMPV) co-infection. RSV-hMPV coinfection was found to be associated with a higher risk of ICU admission (odds ratio (OR) = 7.2, 95% confidence interval (CI) = 2.1-25.1; OR after removal of the most influential study was 3.7, 95% CI = 1.1-12.3). We also observed a trend from three studies that RSV-hMPV coinfections were likely to be associated with longer hospital stay.

Conclusion

Our findings suggest that RSV-hMPV coinfections might be associated with increased risk for ICU admission in children <5y compared with RSV mono-infection but such association does not imply causation. Our findings do not support the association between RSV coinfections with other viruses and clinical severity but further large-scale investigations are needed to confirm the findings.

Protocol registration

PROSPERO CRD42019154761.