Methods: Between 2002 and 2006 a multicenter study was conducted among such high risk children <24 months of age admitted with aLRTI to determine the prevalence of human metapneumovirus (HMPV). Nasopharyngeal aspirates were tested for HMPV and RSV using PCR. Demographic, epidemiological, and clinical data were collected including palivizumab administration within the preceding 30 days. A test-negative case-control design was used to determine palivizumab effectiveness (PE). We compared the odds of palivizumab administration between RSV cases and controls (OR). RSV PE (%) was estimated as (1-OR) x 100. This analysis is restricted to the RSV season (November – April) in US and Canadian sites.
Results: Of 1162 enrolled children, 849 (73%) were eligible. Exclusions primarily included enrollment outside the US or Canada (184) or outside the RSV season (93). Palivizumab was used in 434 children (51%). Palivizumab use was more common among those who were older (6.2 vs 3.8 mo), were more premature (29 vs 34 wGA), had lower birthweight (1,300 vs 2,150 g), had prior NICU admission (91% vs 74%), and had a longer NICU admission (64 vs 18 d) (p <0.0001 for all comparisons). RSV was identified in 403 infants (47.5%). The PE point estimate was 43% (95% CI, 34 – 51%). In contrast, the PE point estimate was -4% against HMPV (95% CI, -55% to 30%) among RSV negative children.
Conclusion: Using a test-negative case-control design with molecular detection of RSV, Palivizumab effectiveness was 43% (95% CI, 34 – 51%) against aLRTI requiring hospitalization but confounding likely lowered this point estimate.
E. J. Anderson,
MedImmune: Investigator , Research grant
Roche: Editorial assistance in writing a manuscript , Editorial assistance in writing a manuscript
R. Yogev, MedImmune: Speaker's Bureau , Speaker honorarium
J. Yi, None
E. A. F. Simões, MedImmune: Grant Investigator and Scientific Advisor , Consulting fee and Research grant