Health-related quality of life and adverse events during 14 days after receiving a live-attenuated influenza vaccine in Japanese children 4–15 years of age

No data have been collected regarding the quality of life after live-attenuated influenza vaccine (LAIV). Our study investigates LAIV's impact on the quality of life of children. This prospective, questionnaire-based study targeted children aged 4-15 y. Guardians responded to daily surveys for 16 d, starting the day before vaccination. The questionnaire included the EuroQoL 5-dimension Youth 3-Level (EQ-5D-Y-3L) tool and the EuroQoL Visual Analogue Scale (EQ-VAS) monitoring fluctuations of health-related quality of life (HRQL) and adverse events following immunization (AEFIs). Time series analysis and area under the curve (AUC) calculation were used to investigate the scores' changes. Final analysis involved 92 patients who responded to at least half of the questionnaire's iterations, including both day 7 and 14 after vaccination. One or more AEFIs were reported for 78 children (73.91%), with generally mild symptoms. In 30 cases, a significant impact on daily activities was described, and one serious AEFI was reported consisting of severe headache and pharyngodynia with fever, leading to emergency room access. EQ-VAS score dropped on the first 2 d after vaccination and recovered thereafter, reaching (and even exceeding) the pre-vaccination value on day 10. The EQ-5D-Y-3L score also declined, however, only on day 1 and recovered faster, reaching the pre-vaccination value already on day 5, undulating around the baseline level until day 10. A net loss of 0.01 quality-adjusted life days was identified (AUC: -0.0138). Our analysis showed a positive LAIV safety profile. Data from larger populations are needed to support clinical recommendations, promoting vaccine acceptance and fighting hesitancy.