Objective: To analyze the effects of inactivated influenza vaccine in children with moderate to severe allergic rhinitis on influenza-like illness (ILI) and wheezy episode after ILI.

Material and Method: A cross sectional non-randomized patient preference study was performed on 314 children with moderate to severe allergic rhinitis who attended the Pediatric Allergy clinic between June 2015 and July 2016 in Chiang Rai Hospital. One hundred sixty two patients were immunized with an influenza vaccine (quadrivalent influenza vaccine). ILIs and wheezy episodes were compared between the immunized and the un-immunized groups. The present study compared between the age groups of younger children (younger than 7 years) and older children (7 to 15 years).

Results: The two study groups had similar demographic and clinical characteristics in younger and older children except with regards to co-morbid asthma, snoring child, positive skin prick test to American cockroach in younger children, and family incomes, co-morbid asthma, rhino-sinusitis in older children including allergic rhinitis controllers usage and skin prick testing results. One year after the vaccine was administered, the immunized group had significantly reduced ILIs, wheezy episodes, and severity of asthmatic events in children with co-morbid mild persistent asthma (ER visits, medical usages for wheezy episode, hospitalizations, and their duration) in both younger and older children (p<0.05).

Conclusion: Immunization of inactivated influenza vaccine is beneficial in children with moderate to severe allergic rhinitis, it can reduce ILIs, wheezy episodes, and severity of asthmatic events in children with co-morbid mild persistent asthma.

Keywords: Quadrivalent influenza vaccine, Wheezy episodes, Moderate to severe allergic rhinitis, Children, Thailand