Lin Y.-J.Wen C.-N.Lin Y.-Y.Hsieh W.-C.Chang C.-C.Chen Y.-H.Hsu C.-H.Shih Y.-J.Chen C.-H.CHI-TAI FANG2020-05-192020-05-1920202041-1723https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077942211&doi=10.1038%2fs41467-019-14230-x&partnerID=40&md5=ed906e69153564d18161d28ca8c7fff6https://scholars.lib.ntu.edu.tw/handle/123456789/493724Standard inactivated influenza vaccines are poorly immunogenic in immunologically naive healthy young children, who are particularly vulnerable to complications from influenza. For them, there is an unmet need for better influenza vaccines. Oil-in-water emulsion-adjuvanted influenza vaccines are promising candidates, but clinical trials yielded inconsistent results. Here, we meta-analyze randomized controlled trials with efficacy data (3 trials, n = 15,310) and immunogenicity data (17 trials, n = 9062). Compared with non-adjuvanted counterparts, adjuvanted influenza vaccines provide a significantly better protection (weighted estimate for risk ratio of RT-PCR-confirmed influenza: 0.26) and are significantly more immunogenic (weighted estimates for seroprotection rate ratio: 4.6 to 7.9) in healthy immunologically naive young children. Nevertheless, in immunologically non-naive children, adjuvanted and non-adjuvanted vaccines provide similar protection and are similarly immunogenic. These results indicate that oil-in-water emulsion adjuvant improves the efficacy of inactivated influenza vaccines in healthy young children at the first-time seasonal influenza vaccination. ? 2020, The Author(s).English[SDGs]SDG3adjuvant; influenza vaccine; water oil cream; immunological adjuvant; influenza vaccine; oil; virus antibody; water; child health; emulsion; health risk; immune system; influenza; meta-analysis; vaccination; vaccine; vulnerability; adverse event; appendicitis; Article; asthma; convulsion; cranial nerve paralysis; death; diabetes mellitus; febrile convulsion; gastroenteritis; Guillain Barre syndrome; hospitalization; human; immunogenicity; influenza; influenza vaccination; meta analysis; multiple sclerosis; narcolepsy; nervous system inflammation; neurologic disease; outcome assessment; pneumonia; randomized controlled trial (topic); real time polymerase chain reaction; seroprevalence; systematic review; vaccination; antibody production; blood; chemistry; child; emulsion; factual database; immunity; immunology; influenza; Orthomyxoviridae; vaccination; Adjuvants, Immunologic; Antibodies, Viral; Antibody Formation; Child; Databases, Factual; Emulsions; Humans; Immunity; Influenza Vaccines; Influenza, Human; Oils; Orthomyxoviridae; Vaccination; Waterjournal article10.1038/s41467-019-14230-x319491372-s2.0-85077942211