Does the Covid-19 vaccine cause late periods?

Many women have reported late periods after being vaccinated against Covid-19. They now have proof of a causal link. Researchers at the University of Portland (USA) studied the menstrual cycles of nearly 20,000 women, before and after each dose of vaccine. On average, when a woman receives a dose of vaccine, her normally 28-day cycle is disrupted by one day, before returning to normal in the next cycle.

The menstrual cycle is often disturbed by external factors, recalls Isabelle Héron, an obstetrician-gynecologist. “A serious infection or a high fever can generate cycle disorders”, she explains. There is therefore a link between the vaccine against Covid-19 and possible menstrual disorders, according to the American study. But this disorder remains weak, temporary, and no consequences on fertility have been observed.