THE EFFECT OF POSSIBLE WHEEZING ADVERSE EVENTS ON THE COST-EFFECTIVENESS OF NASAL INFLUENZA VACCINE IN CHILDREN

Purpose:  A recent randomized controlled trial among children <5 years of age found that live attenuated influenza vaccine (LAIV) was more effective in preventing laboratory-confirmed influenza compared to inactivated influenza vaccine (IIV). However, these new data suggest an increase in adverse events, such as wheezing, in children less than 5 years of age for LAIV compared to IIV. LAIV is now licensed for children 2 years or older without a history of wheezing or asthma. This study incorporated new data on adverse events into a validated model of the cost-effectiveness of influenza vaccination in children.

 

Methods:  A decision tree was developed to predict the costs and health effects of no vaccination, vaccination with IIV, and vaccination with LAIV for healthy children aged 6-23 months, 2 years, and 3-4 years.  Probabilities, costs (direct and opportunity), and quality adjustments for uncomplicated influenza, outpatient visits, hospitalizations, deaths, vaccination and vaccine adverse events were based on primary and published data.  The model included the possible increased incidence of adverse events following vaccination for LAIV, including fever, wheezing, and hospitalization. Cohorts of 1,000 children were considered separately for each age group. The primary endpoint was the incremental cost-effectiveness ratio.  Sensitivity analyses, including a probabilistic sensitivity analysis, were conducted.  A societal perspective was used.  The analysis used a time horizon of one year and also included losses beyond one year associated with long-term sequelae (discounted at 3% per annum).

 

Results:  Cost-effectiveness ratios ranged from $20,000/QALY (6-23 months) to $33,000/QALY (3-4 years) for LAIV and from $21,000-$37,000 for IIV.  Inclusion of possible new adverse events for LAIV had varying effects on cost-effectiveness results.  Results were not sensitive to the inclusion of wheezing as an adverse event but were very sensitive to including a possible increased probability of hospitalization.  Overall, cost-effectiveness ratios increased by 5-10%, depending on age, with the inclusion of wheezing-related adverse events.

 

Conclusions:  LAIV had cost-effectiveness ratios within the same range as other recently recommended vaccines.  It remained more effective than IIV for children younger than 5 years under a wide range of assumptions about adverse event rates.  The results were sensitive to an increase in the probability of hospitalization at the highest rates evaluated; post-licensing safety studies of both live and inactivated influenza vaccines in children should continue.