Estimates of the Public Health Impact of a Pediatric Vaccination Program Using an Intranasal Tetravalent Live-Attenuated Influenza Vaccine in Belgium.
OBJECTIVE
Our objectives were to estimate the public health outcomes of vaccinating Belgian children using an intranasal tetravalent live-attenuated influenza vaccine (QLAIV) combined with current coverage of high-risk/elderly individuals using the trivalent inactivated vaccine.


METHODS
We used a deterministic, age-structured, dynamic model to simulate seasonal influenza transmission in the Belgian population under the current coverage or after extending vaccination with QLAIV to healthy children aged 2-17 years. Differential equations describe demographic changes, exposure to infectious individuals, infection recovery, and immunity dynamics. The basic reproduction number (R 0) was calibrated to the observed number of influenza doctor visits/year. Vaccine efficacy was 80 % (live-attenuated) and 59-68 % (inactivated). The 10-year incidence of symptomatic influenza was calculated with different coverage scenarios (add-on to current coverage).


RESULTS
Model calibration yielded R 0 = 1.1. QLAIV coverage of 75 % of those aged 2-17 years averted 374,000 symptomatic cases/year (57 % of the current number), 244,000 of which were among adults (indirect effect). Vaccinating 75 % of those aged 2-11 years and 50 % of those aged 12-17 years averted 333,200 cases/year (213,000 adult cases/year). Vaccinating only healthy children aged 2-5 years generated direct protection but limited indirect protection, even with 90 % coverage (40,800 averted adult cases/year; -8.4 %). Targeting all children averted twice as many high-risk cases as targeting high-risk children only (8485 vs. 4965/year with 75 % coverage). Sensitivity analyses showed the robustness of results.


CONCLUSIONS
The model highlights the direct and indirect protection benefits when vaccinating healthy children with QLAIV in Belgium. Policies targeting only high-risk individuals or the youngest provide limited herd protection, as school-age children are important influenza vectors in the community.
IMS Health Real-World Evidence Solutions, Corporate Village, Davos Building, Da Vincilaan 7, 1935, Zaventem, Belgium. LGerlier@be.imshealth.com.
Laetitia
L
Gerlier
IMS Health Real-World Evidence Solutions, Corporate Village, Davos Building, Da Vincilaan 7, 1935, Zaventem, Belgium.
Mark
M
Lamotte
S.A. AstraZeneca N.V., Uccle, Belgium.
Sofia
S
Dos Santos Mendes
Bielefeld University, Bielefeld, Germany.
Oliver
O
Damm
ExploSYS GmbH, Leinfelden-Echterdingen, Germany.
Markus
M
Schwehm
Institute for Clinical Epidemiology and Applied Biometry, University of Tübingen, Tübingen, Germany.|Epimos GmbH, Dusslingen, Germany.
Martin
M
Eichner
D000281:Administration, Intranasal; D000293:Adolescent; D001530:Belgium; D002648:Child; D002675:Child, Preschool; D006801:Humans; D017589:Immunization Programs / Q000379:methods*; D007252:Influenza Vaccines / Q000008:administration & dosage*; D007251:Influenza, Human / Q000517:prevention & control*; D011634:Public Health; D012306:Risk; D014611:Vaccination / Q000379:methods; D014613:Vaccines, Attenuated / Q000008:administration & dosage
D007252:Influenza Vaccines; D014613:Vaccines, Attenuated