The authors note that inactivated, trivalent, injectable influenza vaccine (injectable vaccine) is the only formulation approved for use in high-risk children, owing in part to concerns that live attenuated influenza vaccine (given nasally) might worsen asthma symptoms in asthmatics. This paper reports the results of an efficacy and safety trial of a reformulated live attenuated vaccine (live vaccine).
Subjects were European children aged 6-17 years with asthma enrolled during the 2002-2003 influenza season. The study excluded children with many other chronic diseases and children who were immune compromised. For 15 days after vaccination (1:1 randomization to live or injectable vaccine), parents recorded daily asthma symptom scores and peak expiratory flow measurements. In addition, the parents recorded nocturnal symptoms and asthma medication use. After the 15 days of parental log completion, investigators contacted subjects weekly to determine if they required revisit for symptoms. Any subject who developed fever or upper or lower respiratory illness was seen for office visit and nasal swab for influenza culture. The subjects were also monitored for side effects and other unscheduled medical visits. The study enrolled 2229 subjects, with 1114 receiving live vaccine.
There were 123 cases of influenza (5.5% of all subjects), with 4.5% of the live vaccine recipients and 6.6% of the injectable vaccine recipients contracting culture-proven influenza of any strain during the study period. This corresponded to a 31.9% relative efficacy estimate (95% confidence interval 6.6-50.6). Rates of using "any medications" were similar in both groups at approximately 27%, and there was no difference in rates of unscheduled healthcare visits or rates of asthma exacerbation. Rates of rhinitis were higher in the live vaccine group at 9.2% vs 5.5% in the injectable vaccine group. Local inflammation at the injection site was noted in 71% of injectable vaccine recipients. In addition, the injectable vaccine group experienced higher rates of "any wheezing" in the 15 days after vaccine at 23.8% vs 19.5% in the live vaccine group. The rate of serious adverse events was similar in the 2 groups at approximately 1.7% to 1.8% depending on group.
The authors concluded that the new formulation of the live influenza vaccine tested in this study did not increase respiratory events among this group of asthmatic children, and the live vaccine demonstrated a greater relative efficacy compared with injectable vaccine.
Given the challenges the pediatric community faces in delivering any influenza vaccine to at-risk children (see the Dombkowski et al article in the Related Links section), this article provides evidence that formulation of the vaccine may be less of an issue in future seasons. With year-to-year and regional variation in which influenza vaccine preparations are available, being able to utilize the live vaccine in asthmatics (eventually) will help make sure that we cut down on missed opportunities to immunize.
source - Medscape