title: Partial palivizumab prophylaxis and increased risk of hospitalization due to respiratory syncytial virus in a Medicaid population: a retrospective cohort analysis.
abstract: BACKGROUND
  Infection with respiratory syncytial virus (RSV) is common among young children insured through Medicaid in the United States. Complete and timely dosing with palivizumab is associated with lower risk of RSV-related hospitalizations, but up to 60% of infants who receive palivizumab in Medicaid population do not receive full prophylaxis. The purpose of this study was to evaluate the association of partial palivizumab prophylaxis with the risk of RSV hospitalization among high-risk Medicaid-insured infants.
  
  
  METHODS
  Claims data from 12 states during 6 RSV seasons (October 1st to April 30th in the first year of life in 2003-2009) were analyzed. Inclusion criteria were birth hospital discharge before October 1st, continuous insurance eligibility from birth through April 30th, ≥ one palivizumab administration from August 1st to end of season, and high-risk status (≤34 weeks gestational age or chronic lung disease of prematurity [CLDP] or hemodynamically significant congenital heart disease [CHD]). Fully prophylaxed infants received the first palivizumab dose by November 30th with no gaps >35 days up to the first RSV-related hospitalization or end of follow-up. All other infants were categorized as partially prophylaxed.
  
  
  RESULTS
  Of the 8,443 high-risk infants evaluated, 67% (5,615) received partial prophylaxis. Partially prophylaxed infants were more likely to have RSV-related hospitalization than fully prophylaxed infants (11.7% versus 7.9%, p< 0.001). RSV-related hospitalization rates ranged from 8.5% to 24.8% in premature, CHD, and CLDP infants with partial prophylaxis. After adjusting for potential confounders, logistic regression showed that partially prophylaxed infants had a 21% greater odds of hospitalization compared with fully prophylaxed infants (odds ratio 1.21, 95% confidence interval 1.09-1.34).
  
  
  CONCLUSIONS
  RSV-related hospitalization rates were significantly higher in high-risk Medicaid infants with partial palivizumab prophylaxis compared with fully prophylaxed infants. These findings suggest that reduced and/or delayed dosing is less effective.
authors.affiliation: Children's Medical Center, Winthrop University Hospital, Mineola, NY, USA. LKrilov@Winthrop.org.
authors.forename: Leonard R
authors.initials: LR
authors.lastname: Krilov
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Masaquel
authors.forename: Leonard B
authors.initials: LB
authors.lastname: Weiner
authors.forename: David M
authors.initials: DM
authors.lastname: Smith
authors.forename: Sally W
authors.initials: SW
authors.lastname: Wade
authors.forename: Parthiv J
authors.initials: PJ
authors.lastname: Mahadevia
mesh_terms: D000367:Age Factors; D000998:Antiviral Agents / Q000008:administration & dosage*; D018890:Chemoprevention; D015331:Cohort Studies; D004334:Drug Administration Schedule; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008297:Male; D008484:Medicaid; D000069455:Palivizumab / Q000008:administration & dosage*; D044469:Racial Groups / Q000706:statistics & numerical data; D018357:Respiratory Syncytial Virus Infections / Q000453:epidemiology / Q000517:prevention & control*; D012189:Retrospective Studies; D012424:Rural Population / Q000706:statistics & numerical data; D012737:Sex Factors; D014481:United States / Q000453:epidemiology
chemical_list: D000998:Antiviral Agents; D000069455:Palivizumab