[theold]

Overall, the data showed that COVID-19 vaccination was associated with small (but still statistically significant) increase to a person's menstrual cycle by about one day. In some people who received two COVID-19 shots over the course of one menstrual cycle, a two-day increase in cycle length was observed. There were no significant effects on period length itself, and, on average, cycles returned to normal after one month of being abnormal.

But while the vaccine can have a short-term effect on periods, it's important to remember that contracting COVID-19 could have an even longer effect.

https://www.health.com/condition/infecti...cle-period