To determine the population-based inpatient disease burden of parainfluenza virus in children <5 years of age.

The New Vaccine Surveillance Network (NVSN) enrolled children <5 years of age who were hospitalized with febrile or acute respiratory illnesses. Surveillance hospitals admitted >95% of all hospitalized children from each county. Combined nasal turbinate/throat swabs were tested for parainfluenza virus (PIV), respiratory syncytial virus, and influenza virus with culture and reverse-transcription-polymerase chain reaction. Both parental interviews and medical chart reviews were conducted. Age-specific population-based hospitalization rates were calculated.

From October 2000 through September 2004, 2798 children were enrolled. A total of 191 PIVs were identified from 189 children (6.8% of enrolled: 73 PIV type 1, 23 PIV type 2, and 95 PIV type 3), compared with 521 respiratory syncytial viruses and 159 influenza viruses. Mean PIV hospitalization rates were 3.01, 1.73, 1.53, 0.39, and 1.02 per 1000 children per year for ages 0 to 5 months, 6 to 11 months, 12 to 23 months, 24 to 59 months, and 0 to 59 months, respectively.

PIV accounted for 6.8% of all hospitalizations for fever, acute respiratory illnesses, or both in children <5 years of age. The pediatric PIV inpatient burden is substantial and highlights the need to find an effective vaccine candidate.