Study On Effectiveness And Antibody Response Of Quadrivalent Influenza Vaccine For The Elderly In Nursing Home Of Guangdong Province

BackgroundAnnual vaccination is the most effective way to prevent the elderly from influenza infection.Yet vaccine effectiveness has been inconsistent across regions and seasons,which impairs vaccination among the elderly.In 2018,Guangdong province provided free quadrivalent influenza vaccine to elderly people over 60 years old in nursing homes.It helps to systematacially determine the protective effect of influenza vaccine for the elderly.ObjectiveBy researching the seasonal characteristics of influenza among the elderly in Guangdong Province,and the antibody response and vaccine effectiveness for the vaccinated elderly,this study provides evidence for making the influenza vaccination strategy for the elderly in Guangdong.Methods1.To collect the proportion of weekly influenza-like illness outpatient visiting(ILI%)and the positive rate of influenza virus nucleic acid test in the elderly in Guangdong province from 2011/2012 to 2019/2020 and to make MEM epidemic threshold model.2.A total of 2109 elderly subjects from nursing home were selected for a conhort study.The incidence and death of respiratory diseases and medical expenses of the subjects were collected monthly in 2018 and 2019.Vaccine effectiveness and benefit-cost ratio were calculated.3.A total of 450 elderly in nursing homes were enrolled.Serum samples were collected before and 1 month after influenza vaccination to measure hemagglutinin inhibition(HI)antibodies and Neuraminidase inhibition(NI)antibodies.Blood samples were collected at 6 and 9 months to determine HI antibodies.Logistics regression was used to analyze the impact factors of antibody seroconversion and persistence.4.Thirty elderly subjects with high and low HI antibody levels were selected after vaccination.ELISA was used to detect 24 types of influenza virus hemagglutinin IgG antibodies.Results1.Weekly ILI%peak value was 4.91%-7.54%.The seasonal peak of the elderly occurred in winter,spring and summer,and the highest weekly positive rate was 57.14%.2.Old adults had a lower risk of death from respiratory disease within 12 months of vaccination than the unvaccinated group.The vaccine effectiveness was 80%(95%CI:12%,96%).The median hospitalization cost was 5,225 yuan(IQR:3955-9852)in the vaccination group and 10,080 yuan(IQR:4326-22029)in the unvaccinated group.The difference was statistically significant(Z=-2.05,P=0.04).3.At 30 days after vaccination,361(80.22%)of the elderly had HI antibody conversion to at least one vaccine component.Thirty-five patients(7.78%)had HI antibody conversion to all four vaccine components.HI antibodys decreased significantly at 6 or 9 months after vaccination.There were 270(60%)older adults who had NI antibodies conversion to at least one vaccine component,and 17(3.78%)of them had NI antibodies conversion to all four vaccine strains.4.After vaccination,the high response group mainly produced antibody cross-reaction against human influenza A virus,and parts of the subjects also had antibody against avian influenza virus subtypes.ConclusionThis study found that influenza vaccination can effectively reduce the risk of death and hospitalization costs for the aged people in nursing houses.The antibody response of the elderly after vaccination was low and the protective level of antibody decreased significantly 6 months after vaccination.Antibody cross-reaction was observed yet did not hamper vaccine component antibody production.The findings suggest to improve influenza vaccination strategies for aged people,including optimize vaccination timing and selection of highly immunogenic vaccines.