Female-to-male trans (FtM) individuals report irregular periods after receiving the Covid-19 mRNA vaccine.
FtM trans whose menstrual periods stopped while on the male hormone testosterone now complain that they are menstruating again.
Biological women in the LGBT and heterosexual communities report irregular menstruation such as heavy bleeding after taking Covid-19 mRNA vaccines.
A few FtM trans took to social media to vent their frustration.
One FtM trans who hasn't had a period in 5 years started menstruating spontaneously within days of taking the Moderna injection.
A heterosexual woman wrote that her 24-year-old biological sister, who self-identifies as a male, began bleeding heavily after taking the vaccine.
"He was very unprepared, and in shock at Aunt Mary's return," she wrote in a post on Reddit.com. "Aunt Mary" is slang for menstruation.
She added: "I'm worried it may affect my cycle if I get it? I'm very regular; you could set a clock to my cycle."
Researchers have launched a study to determine whether Covid-19 mRNA vaccines cause abnormal periods such as heavy bleeding.
200 million adults and children in America have been vaccinated -- more than half of the U.S. population.
But the pace of vaccinations has begun to slow, because people who don't want the vaccine are not seeking appointments.
The White House and the CDC are concerned the U.S. might not reach herd immunity, as those who are fully vaccinated begin to fall ill from Covid-19.
While New Hampshire has given at least one shot to 59 percent of its citizens, states such as Mississippi, Alabama, Georgia and Florida are at or below 30 percent vaccinated.
"There are states where they feel they have hit the wall," said Michael Fraser, the executive director of the Association of State and Territorial Health Officials. "The folks that wanted [vaccines] have found it. The folks that don't want it are not bothering to find it."