Background The impact of neuraminidase inhibitors (NAIs) on influenza-related
pneumonia (IRP) is not established. Our objective was to investigate the
association between NAI treatment and IRP incidence and outcomes in patients
hospitalised with A(H1N1)pdm09 virus infection. Methods A worldwide meta-
analysis of individual participant data from 20 634 hospitalised patients with
laboratory-confirmed A(H1N1)pdm09 (n = 20 021) or clinically diagnosed (n =
613) ‘pandemic influenza’. The primary outcome was radiologically confirmed
IRP. Odds ratios (OR) were estimated using generalised linear mixed modelling,
adjusting for NAI treatment propensity, antibiotics and corticosteroids.
Results Of 20 634 included participants, 5978 (29·0%) had IRP; conversely,
3349 (16·2%) had confirmed the absence of radiographic pneumonia (the
comparator). Early NAI treatment (within 2 days of symptom onset) versus no
NAI was not significantly associated with IRP [adj. OR 0·83 (95% CI 0·64–1·06;
P = 0·136)]. Among the 5978 patients with IRP, early NAI treatment versus none
did not impact on mortality [adj. OR = 0·72 (0·44–1·17; P = 0·180)] or
likelihood of requiring ventilatory support [adj. OR = 1·17 (0·71–1·92; P =
0·537)], but early treatment versus later significantly reduced mortality
[adj. OR = 0·70 (0·55–0·88; P = 0·003)] and likelihood of requiring
ventilatory support [adj. OR = 0·68 (0·54–0·85; P = 0·001)]. Conclusions Early
NAI treatment of patients hospitalised with A(H1N1)pdm09 virus infection
versus no treatment did not reduce the likelihood of IRP. However, in patients
who developed IRP, early NAI treatment versus later reduced the likelihood of
mortality and needing ventilatory support