Kuijpers, YunusPicavet, H Susan Jde Rond, Liade Zeeuw-Brouwer, Mary-LèneRutkens, RyanneGijsbers, EstherSlits, IreneEngelfriet, PeterBuisman, Anne-MarieVerschuren, W M Monique2023-11-012023-11-012023-10-251742-49333788075810.1186/s12979-023-00382-4http://hdl.handle.net/10029/627040We included 1457 persons aged 50 to 92 years old. Of these persons 1257 were infection naïve after their primary vaccination series. The majority (N = 954) of these individuals were vaccinated with two doses of BNT162b2 (Pfizer) and their data were used for further analysis. A higher frailty index was associated with lower anti-S1 antibody responses at T1 and T2 for both men (RT1 = -0.095, PT1 = 0.05; RT2 = -0.11, PT2 = 0.02) and women (RT1 = -0.24, PT1 < 0.01; RT2 = -0.15, PT2 < 0.01). After correcting for age and sex the frailty index was also associated with the relative increase in anti-S1 IgG concentrations between the two vaccinations (β = 1.6, P < 0.01). Within the construct of frailty, history of a cardiac catheterization, diabetes, gastrointestinal disease, a cognitive speed in the lowest decile of the population distribution, and impaired lung function were associated with lower antibody responses after both vaccinations.en© 2023. BioMed Central Ltd., part of Springer Nature.AgeAntibody responsesCOVID-19 vaccinationComorbidityFrailtyLifestyle deficitsArticleImmun Ageing 2023;20(1):57