Palivizumab is frequently administered for respiratory synctial virus (RSV) prophylaxis to infants at high-risk. Our objective was to determine hospitalization rates and associated risk factors for RSV among infants who received palivizumab.
Data were prospectively gathered on all patients referred for palivizumab in a suburban pediatric pulmonary setting in Atlanta between 1999 and 2003. Data collected included hospitalization for RSV bronchiolitis, gender, gestational age, birthweight, single or multiple birth, number of siblings, smoker in household, daycare attendance, and type of insurance. Patients were seen by a pediatric pulmonologist or a supervised nurse practitioner or physician assistant and were treated for concurrent illnesses during the visits. Patients were reminded about risk factors for RSV infection at each visit.
There were 3,520 patients who received palivizumab during the four-year period; 29 (0.8%) were hospitalized for RSV. The following relationships were found between potential risk factors and hospitalization for RSV:
Hospitalization, n=29No Hospitalization, n=3491OR95% CIGestational age <35 weeks, [n (%)]27 (93.1)2811 (80.5)3.30.8 – 13.8Birthweight <2000 grams, [n (%)]24 (82.8)2361 (67.6)2.30.9 – 6.0Daycare, [n (%)]6 (21.4)366 (11.6)2.10.8 – 5.2Gender (male), [n (%)]19 (67.9)1899 (54.9)1.70.8 – 3.8Medicaid, [n (%)]9 (32.1)840 (24.6)1.50.7 – 3.2Smoker, [n (%)]5 (17.9)406 (12.9)1.50.6 – 3.9Number of siblings, [median (range)]1 (0-3)1 (0-7)0.90.6 – 1.3Multiple birth (2 or more), [n (%)]2 (7.1)1187 (34.3)0.10.1 – 0.6*
* Significant resultsCONCLUSIONS: Patients who received palivizumab had a lower hospitalization rate due to RSV bronchiolitis than the hospitalization rate reported in the published IMpact study (0.8% versus 4.8%). This finding suggests that palivizumab has greater efficacy than previously determined. A comprehensive care model attending monthly to comorbidities, with monthly reminders on avoiding respiratory synctial virus exposure, may have contributed to the lower hospitalization rates. In the current study, those patients who were hospitalized trended toward having had a gestational age <35 weeks, a birthweight <2000 grams, attended daycare, male gender, insured by Medicaid, lived in a household with a smoker, and fewer siblings. Additionally, patients who were a multiple birth (i.e. twin, triplet, etc.) were significantly less likely to be hospitalized for RSV than patients who were a single birth.
Palivizumab is highly effective in preventing RSV in a high-risk population, more so than previously recognized.
B.L. Lesnick, MedImmune, Grant monies.