The incidence ratio for vaccination with LAIV in nonrecommended populations compared with LAIV vaccination in the general population ranged from 0.79 (95% CI, 0.77–0.81) for cohort 3 to 0.012 (95% CI, 0.011–0.013) for cohort 1. Among the 686 cohort 1 children vaccinated with LAIV and without vaccination for the 2009 H1N1 pandemic strain concurrently or during follow-up, there were few lower respiratory outcomes of interest (Table 2). Hospitalization or ED visits for asthma and pneumonia were more frequent RG7204 among LAIV-vaccinated compared with TIV-vaccinated children (difference in frequency of asthma visits, 3.1 [95% CI, −1.9

to 8.0] per 1000; difference in frequency of pneumonia visits, 2.4 [95% CI, −2.6 to 7.3] per 1000). The frequency of any hospitalization or ED visit was similar among LAIV and TIV recipients. Among the 8308 children aged 24 through 59 months with asthma or wheezing vaccinated with LAIV and without vaccination for H1N1 concurrently or during follow-up, there were few lower respiratory outcomes of interest (Table 3). Hospitalization or ED visits for each LRI evaluated were not more frequent among LAIV-vaccinated compared with TIV-vaccinated children. The frequency of any hospitalization or ED visit among LAIV recipients did not show an excess relative to that among TIV recipients. Of the

361 LAIV-vaccinated children in cohort 4, 229 (63%) qualified as immunocompromised because of a prescription for systemic corticosteroids, while 64 (18%) LEE011 qualified due to a diagnosis code for chemotherapy, 55 (15%) qualified due medroxyprogesterone to congenital immune deficiency, and 8 (2%) qualified due to a hematologic or lymphatic cancer. After excluding 37 (10%) children with a 2009 H1N1 pandemic vaccination, among the remaining 324 LAIV-vaccinated children with immunocompromise, 14 children experienced an ED visit for common childhood conditions and injuries; there were

no hospitalizations. Six were associated with primary diagnosis codes that could be considered infectious diseases (3 for croup and 1 each for pharyngitis, acute respiratory infection, and otitis media), for a frequency of 18.5 (95% CI, 6.8–39.9) per 1000 vaccinations, compared with a frequency of 53.8 (95% CI, 43.5–65.8) per 1000 immunocompromised TIV-vaccinated children. The rate of ED visitation or hospitalization among LAIV recipients was 43.2 (95% CI, 23.6–72.5) per 1000 vaccinations, and among TIV-vaccinated children was 237 per 1765 vaccinations (134 [95% CI, 118–152] per 1000 vaccinations). Over the 3 seasons of the entire study period, cumulative LAIV vaccinations included in the denominators for the annual safety analyses were 1361 children <24 months, 11,353 children with asthma or wheezing, and 425 immunocompromised children. As in previous years [2], the low rates of vaccination with LAIV in cohorts 1, 2, and 4 indicate that healthcare providers in general are complying with the product labeling.