Infants with CF incurring respiratory virus infection are at significant risk for LRTI, for hospitalization, and for deterioration in lung function that persists months after the acute illness.

Efficacy of the PFP-2 vaccine against lower respiratory tract illness during the RSV season was shown in RSV-seropositive children with CF.

Summary. Background: Human metapneumovirus (hMPV) has been isolated from children with acute respiratory infection worldwide. Its epidemiology remains to be defined in children with cystic fibrosis (CF). We describe the epidemiology and clinical impact of hMPV in CF children and compared it to respiratory syncytial virus (RSV). Methods: CF children ages 7-18 years were studied prospectively during the 1998-1999 RSV season. Nasopharyngeal specimens were collected during acute respiratory illnesses and tested for respiratory viruses. Blood specimens were drawn early, mid, and end of the RSV season, and tested for serological evidence of hMPV and RSV infections. Rates of lower respiratory tract illnesses (LRTI) and hospitalizations for pulmonary exacerbations were compared during the time intervals they developed serological evidence of infection to their non-infection intervals. Results: Six of 44 CF children had a virus positive respiratory illness in 56 LTRI events and 18 hospitalizations. Serological evidence of hMPV and RSV infections occurred in 16 and 20 CF children, respectively; 8 had infections with both viruses. A greater proportion of CF children had !1 LRTI during their infection intervals compared to their non-infection intervals (13/25 vs. 5/25; P ¼ 0.03). A trend for higher rates of LRTI was observed in the infection intervals compared to noninfection intervals (9.5 AE 11.0 vs. 4.2 AE 9.9 per 1,000 child-days; P ¼ 0.06), and it was significantly greater with a more conservative estimate (one event per child per interval; 7.4 AE 7.7 vs. 2.6 AE 5.4 per 1,000 child-days; P 0.01). No differences in hospitalizations rates were detected. Conclusion: The infection rates and clinical impact observed for hMPV were comparable to that for RSV in CF children 7-18 years of age.

Sequential annual PFP-2 vaccination was safe and not associated with exaggerated respiratory disease.