IFNL3 and COVID-19: Based on the results obtained in this study, it is possible to conclude that: (1) Remarkable immunogenicity for SARS-CoV-2 antigens was present in the older adults vaccinated with ChadOx-1; (2) CMV seropositivity negatively impacted the specific IgG response to COVID-19; and (3) The heterozygosis (C/T) and mainly the homozygosis for allele 1 (C/C) in the il28b gene, which encodes an IFN-lambda-3 cytokine, could putatively be an important factor to be assessed in the specific antibody response to COVID-19 in older adults seropositive for CMV.