Adult-onset Still's disease after ChAdOx1 nCoV-19 vaccine: a possible association.

With emergent Sars-Cov-2, a highly transmissive virus that caused millions of deaths worldwide, the development of vaccines became urgent to combat COVID-19. Although rare, important adverse effects had been described in a hypothetical scenario of immune system overstimulation or overreaction. Still's disease is a rare inflammatory syndrome of unknown etiology.