Pneumococcal coinfection with human Metapneumovirus

Background. Infection with the newly discovered human metapneumovirus (hMPV) may lead to hospitalization of children with lower respiratory tract infection (LRTI), although the pathogenesis thereof remains to be elucidated. Methods. This hypothesis-generating study involved a cohort of children randomized to receive 9-valent conjugate pneumococcal vaccine or placebo and who were tested for hMPV infection when hospitalized for LRTI. By use of a nested reverse-transcription polymerase chain reaction assay targeted at amplifying a fragment of the hMPV fusion ( F) protein gene, 202 such infections were identified among 2715 episodes of LRTI in children. Results. Among human immunodeficiency virus (HIV)-uninfected children who had received 3 doses of conjugate pneumococcal vaccine, the incidence of hMPV-associated LRTI was reduced by 45% (95% confidence interval [CI],19%- 62%; P = 0.002), and the incidence of clinical pneumonia was reduced by 55% ( 95% CI, 22%- 74%; P = .003). Similarly, in fully vaccinated HIV- infected children, the incidence of hMPV-associated LRTI was reduced by 53% ( 95% CI, 3% - 77%; P = .035 ), and that of clinical pneumonia was reduced by 65% ( 95% CI, 19% - 85%; P = .020). Conclusions. The pathogenesis of hMPV- associated LRTI that results in hospitalization of both HIV- infected and - uninfected children involves bacterial coinfection with pneumococcus, and a significant proportion of these hospitalizations may be prevented by vaccination with pneumococcal conjugate vaccine.