The Norwegian Medicines Agency has so far processed 1,264 reports of menstrual disorders after COVID-19 vaccination.
Some of the women lost their periods completely, others experienced bleeding after menopause, whereas many women suffered from more pain and heavier bleeding, TV2 has reported.
Doctor Lill Trogstad of the Norwegian Institute of Public Health (FHI) said that the connection between the menstrual disorders and vaccines cannot be ruled out.
"The women who reported these are not the ones who bled one extra day. Some had to receive treatment to stop the bleeding, and others have been bleeding for weeks", Trogstad said. "We take these reports seriously and go to great lengths to study any connections", she added.
The reported side effects were said to be related to all three vaccines used in the Norwegian vaccination programme (Pfizer, Moderna, and AstraZeneca). According to the Medicines Agency, it is currently impossible to say whether any of these stands out.
"We must not downplay this. There are significant ailments, but menstrual disorders are a common phenomenon. Therefore, it is difficult to come to a definite conclusion. We don't rule out that there may be a connection between the vaccines and menstrual disorders", Norwegian Medicines Agency chief physician Sigurd Hortemo told the newspaper Nettavisen.
Both the Norwegian Medicines Agency and the FHI ventured that there are far more women who have experienced menstrual disorders after the vaccine than those who have come forward.
"We are pretty sure that it is a dark number", Hortemo of the Norwegian Medicines Agency told TV2. "We reckon that there are many women who experienced menstrual disorders, without reporting them".
"We are pretty sure that it is a dark number", Hortemo of the Norwegian Medicines Agency told TV2. "We reckon that there are many women who experienced menstrual disorders, without reporting them".
This was confirmed by TV2's own survey. Of the more than 200 women who experienced changes in their period patterns after the vaccine, merely 35 percent reported them.
Over the course of the pandemic, the Norwegian Medicines Agency has received a total of 37,859 reports of side effects after vaccination. Of these, a huge backlog of 17,000 reports remains unprocessed, indicating that the number of reported menstrual disturbances may rise further.
To get to the bottom of the issue, the FHI will now follow up with 60,000 Norwegian women aged between 11 and 80 to map their bleeding patterns and get reliable answers as to whether the menstrual disorders are vaccine-related or not.
Still, the FHI emphasised it currently lacks any evidence that the disturbances are dangerous or could lead to permanent changes. So far, there have been no changes to the health recommendations for women. The Norwegian health authorities insist that all adults over the age of 18 should take the COVID shot.