Human respiratory syncytial virus and other viral infections in infants receiving palivizumab

BackgroundPalivizumab is a humanized monoclonal antibody that prevents severe human respiratory syncytial virus (HRSV) infections.ObjectivesWe determined the etiology of respiratory viral infections in palivizumab recipients, and monitored the clinical outcome and HRSV genotype in HRSV-infected infants.Study designNasopharyngeal aspirates (NPAs) were collected from children receiving palivizumab who consulted or were hospitalized for acute respiratory tract infection (ARTI) during the 2004–2005 season. Viral cultures and multiplex RT-PCR for influenza A/B, HRSV and human metapneumovirus were performed. The fusion (F) gene of HRSV amplicons was also sequenced.ResultsAmong 116 enrolled patients, 51 (44%) had ≥1 episode of ARTI for a total of 93 visits. At least one virus was identified in 33 (36%) of the 93 NPA samples; HRSV accounted for 11 (33%) of confirmed viral etiologies. Compared to subjects who had other viral ARTI, HRSV-positive subjects had less fever (p = 0.01) and tended to have more bronchiolitis (p = 0.07). Ten subjects (11 visits) developed HRSV infection, although only one was hospitalized. HRSV was detected after a median of 5.5 palivizumab doses and a median of 14 days after the last dose. One of the 11 HRSV strains tested had a F mutation located in the palivizumab-binding site.ConclusionHRSV is still a major cause of ARTI in children receiving palivizumab, although the outcome of infected children appears mild.