This same increase in the use of LAIV in children was observed in another large database of US healthcare claims

data [5]. Continuing the trend observed in the preceding 2 seasons, the somewhat similar rates of LAIV use in those with recurrent wheezing and in the general population suggest that our definition of recurrent wheezing may not match providers’ definitions of recurrent wheezing and may have been overly inclusive. We based our study definition of recurrent wheezing, 1 or more dispensings of a short acting beta agonist in the previous 12 months and the absence of an asthma diagnosis, on the Advisory Committee on Immunization Practices

(ACIP) recommended definition of 1 episode of asthma or wheezing in the previous 12 months. By definition, RGFP966 datasheet recurrent wheezing PARP inhibitor requires multiple episodes of wheezing and frequently in the medical literature a definition of 3 or more episodes is applied over a period of 6–12 months [6], [7], [8], [9], [10], [11] and [12]. The disparity in these definitions and the subsequent vaccination decision-making by clinicians is likely at the root of the less restricted use of LAIV in this population. Across the 3 evaluated seasons, the frequency of safety outcomes was numerically similar among the LAIV-vaccinated children compared with TIV-vaccinated children in all cohorts, except for among children younger than 24 months in the 2009–2010 season. Among the small number of children younger than

24 months who received LAIV compared with those who received TIV, the confidence interval around the difference in rates for asthma hospitalizations or ED visits was −1.9 to 8.0 per 1000 vaccinations and for pneumonia hospitalizations or ED visits was −2.6 to 7.3 per 1000. The numbers of events were too small to make definitive conclusions about the relative frequency of hospitalizations or ED visits for asthma else or pneumonia among LAIV-vaccinated subjects compared with TIV-vaccinated subjects. These observations are consistent with the increased risk of medically significant wheezing previously seen in children 6 through 23 months of age, which resulted in LAIV receiving approval for eligible children 24 months of age and older [7]. In the results described here and in clinical trials, an increased risk of respiratory events following LAIV has not been seen in children 24 months of age and older. Among the 3 evaluated nonrecommended cohorts 24 through 59 months of age, no signals for new or unusual conditions during follow-up were identified during the first 2 study seasons [2] nor during this third and last evaluated season.