The effectiveness of influenza vaccination in primary/secondary school influenza outbreaks in Sichuan province in 2023:a case-control study
Objective To evaluate the effectiveness of influenza vaccine(InfV)with and without prior 23-valent pneumococcal polysaccharide vaccine(PPV23)in primary and secondary school influenza outbreaks.Methods We selected students from 5 schools that had influenza outbreaks in Sichuan during February to April 2023 and conducted a 1∶1 matched case-control study.We analyzed InfV vaccine effectiveness(VE)for three influenza seasons,from 2020 to 2023,and/or PPSV23 given within the last 4.5 years for preventing influenza(including lab-and clinically-confirmed cases)and compared clinical symptom severity scores between vaccinated and unvaccinated influenza cases.Results Each case group and control group included 852 subjects.VEs(95％CI)for InfV vaccination in the 2022/2023,2021/2022,and 2020/2021 influenza seasons were 29.96％(10.24％-45.34％),24.31％(0.09％-42.66％),and 19.00％(-10.37％-40.56％),respectively;VEs(95％CI)for InfV and InfV+PPV23 vaccination in any of the three influenza seasons were 37.15％(22.36％-49.12％)and 34.96％(8.25％-53.89％).In any of the three influenza seasons,median severity scores for InfV-vaccinated and unvaccinated influenza cases were both 9.0 points(Z=-0.08,P=0.938),and for InfV+PPV23-vaccinated and unvaccinated cases were 8.0 and 9.0 points(Z=-3.11,P=0.002).Conclusions Influenza vaccination for primary and secondary school students showed a certain protective effectiveness against influenza;effectiveness declined over the influenza season.InfV vaccination combined with PPV23 can relieve clinical symptoms of influenza.
InfluenzaOutbreakInfluenza vaccine23-valent pneumococcal polysaccharide vaccineVaccine effectivenessPrimary and secondary school
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