In January 2021, my colleagues at the hospital were among the first to receive the Covid-19 vaccine. Comparing the side-effects afterwards, most of us had a sore arm, some of us felt feverish and generally under the weather, but one comment stood out. “My period was heavier than usual,” said one of the midwives. “But that happens to me every year after we get our flu vaccines, too. It’s just another of those vaccine side-effects, isn’t it?”
Was it? I’m an immunologist working in female reproduction and this was the first time I had heard of such an effect, but it didn’t strike me as implausible. We know that various stressors, physical and psychological, can influence the menstrual cycle and vaccination is certainly a physical stressor; those of us who were complaining of feeling under the weather could attest to that. And yet I wondered why, if this effect was as run of the mill as my colleague seemed to think, it wasn’t something I had heard before.
