This study describes a cohort of 223 patients who received anti-S protein monoclonal antibody (mAb) treatment for COVID-19 after having met the indication criteria set by the national guidelines in the Czech Republic at the time. The authors compare the vaccinated and unvaccinated subpopulations of this cohort. The results show that most of the patients (73.5%) already had significant circulating levels of anti-S antibodies detectable at the time of treatment. The authors confirm a positive correlation between number of vaccine doses and S-protein antibody levels. The data show, that vaccinated patients are overall less likely to be hospitalized than unvaccinated ones. The authors recommend a change in the national guidelines for mAb treatment in the Czech Republic.