Effects of Pycnogenol® in people with post-COVID-19 condition (PYCNOVID): study protocol for a single-center, placebo controlled, quadruple-blind, randomized trial

A significant proportion of the global population has been infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at some point since the onset of the pandemic. Although most individuals who develop coronavirus disease 2019 (COVID-19) recover without complications, about 6