doi:10.1111/jam.15699engSerrano, LauraAlgarate, SoniaHerrero-Cortina, BeatrizBueno, JessicaGonzález-Barriga, Maria T.Ducons, MariaMontero-Marco, JesicaAcha, BeatrizTaboada, AnaSanz-Burillo, PilarYuste, CristinaBenito, RafaelRIPOVAC, Study GroupAssessment of humoral immune response to two mRNA SARS-CoV-2 vaccines (Moderna and Pfizer) in healthcare workers fully vaccinated with and without a history of previous infectionART-2022-130128Aims: Presence of anti-S1 region of SARS-CoV-2 spike protein was analysed, at two and eight months, in 477 immunocompetent healthcare workers in Zaragoza, Spain, vaccinated with mRNA-1273 (Moderna) or BNT162b2 (Pfizer). Methods and results: Antibody analysis was performed with Alinity i System (Abbott). At 2 months, 100% of vaccinated had anti-S1 IgG (mean = 13, 285 AU ml-1). This value was significantly higher with Moderna (18, 192 AU ml-1) than with Pfizer (10, 441 AU ml-1). The mean value of anti-S1 IgG after vaccination was significantly higher in patients with than without previous infection (18, 539 vs. 7919 AU ml-1); in both groups was significantly higher with Moderna than with Pfizer (21, 881 vs. 15, 733 AU ml-1 and 11, 949 vs. 6387 AU ml-1), respectively. At 8 months, 100% of patients were IgG positive, with higher levels with Moderna than with Pfizer. Nevertheless, in ensemble of cases, a mean decrease of antibody levels of 11, 025 AU ml-1 was observed. Conclusion: At 2 and 8 months after vaccination, IgG response persists with both vaccines but with important decrease which suggests the need for revaccination. Significance and impact of study: The study contributes to know the immune status after vaccination with two of more used anti-SARS-CoV-2 vaccines. This knowledge is important for establishing the best vaccination strategy. © 2022 The Authors. Journal of Applied Microbiology published by John Wiley & Sons Ltd on behalf of Society for Applied Microbiology.2022http://zaguan.unizar.es/record/12639510.1111/jam.15699http://zaguan.unizar.es/record/126395oai:zaguan.unizar.es:126395Journal of Applied Microbiology 133, 3 (2022), 1969-1974byhttp://creativecommons.org/licenses/by/3.0/es/info:eu-repo/semantics/openAccess