17. October 2021

Separating reproductive health fact from COVID-19 vaccine fiction

Rumour: Vaccines cause infertility by attacking the placenta.

Late last year, Michael Yeadon, a former vice president of Pfizer who lost his job in 2011, co-authored a petition suggesting that the vaccines might cause infertility. Specifically, Yeadon (who also predicted there would be no second wave of the virus and who announced, in November, that the pandemic was over) claimed that a piece of the coronavirus protein (called a “spike protein”) used to make the Pfizer and Moderna vaccines was similar to a protein (called syncytin-1), involved in placental development.

The unsubstantiated theory was that, following vaccination, the antibodies we form to attack the spike proteins might mistakenly go after syncytin-1 (and the placenta) instead thereby causing infertility.

Reality: “That is just nonsensical,” says Dr Alex Polyakov, an obstetrician and senior lecturer at the University of Melbourne’s medical school.

“There are literally millions of vaccinated pregnant women now and placental dysfunction is easy to diagnose as the babies don’t grow well and it translates into a lot of babies being born prematurely or being born small for their gestational age, and that doesn’t exist,” he explains. The reality is that the spike protein and syncytin-1 have different structures and rates of miscarriage or placental abnormalities are similar for both vaccinated and unvaccinated people.

Dr Daryl Cheng, a paediatrician and the medical lead at the Melbourne Vaccine Education Centre, says it simply isn’t true that the body’s antibodies would naturally attack the placenta following COVID-19 illness or vaccination.

He adds that some people may report experiencing issues such as miscarriage or infertility after becoming sick with COVID-19, but this is because the disease can cause other problems, like organ failure and blood clots. This has nothing to do with anything “attacking” the placenta, he says.

Rumour: Vaccines may cause infertility by accumulating in the ovaries.

In a small study submitted to the Japanese equivalent of the TGA, rats were given about 1300 times the Pfizer dose they would give to humans. After 48 hours about 0.1 per cent of the total dose was found in the rats’ ovaries, leading some to suggest that it could cause infertility.

Reality: People spreading that rumour left out several significant details. No one is getting the dose 1300 times higher than prescribed and, Cheng says, to find 0.1 per cent in the ovaries is a “minute amount” even at those high doses.

Even if we dug down into that 0.1 per cent, it was not the genetic material of the spike protein that was accumulating but the fat cell that the vaccine was delivered in, and given ovaries uptake fats and use them to make hormones, this is not a surprise.

“On all levels the claims that people have made about that study are not accurate,” Cheng says, adding that vaccines do not affect sperm count or quality in men either. “It’s one of the big myths out there.”

Rumour: Vaccines could mess with your menstrual cycle and cause endometriosis flare-ups.

Anecdotes abound of women experiencing heavier than normal or irregular periods following their vaccination. Similarly, some women with endometriosis have said they have experienced painful flare-ups of the disorder after their jab.

Reality: This is an active area of research but, according to the experts it is plausible that there is a short-term effect on the menstrual cycle and, possibly, endometriosis symptoms.

There are a couple of reasons for this. The first is that the menstrual cycle is mediated primarily by hormones but also by the immune system. Given that the vaccines cause an immune response, it’s theoretically possible that it affects the complex interplay between immune cells and signals in the uterus.

As endometriosis also has an immune component, there may be a change in symptoms after the vaccine, Polyakov says: “I would have thought it would be a very short-term issue which would happen during the immune response and then come back to normal.”

The second reason may be related to the stress about the vaccine, which can temporarily affect symptoms and the cycle, but should not be confused with any reduction of fertility.

Rumour: You shouldn’t have a vaccination near a mammogram or IVF procedure.

Vaccinations can cause lymph nodes under the arms to swell for several weeks which may affect mammogram results while vaccination side effects like fever may mask post-IVF procedure infections. For these reasons, it has been suggested people avoid having their vaccinations close to their mammogram appointment or IVF treatments.

Reality: IVF is an invasive procedure that has its own risks and it is true that any potential infection could be mistaken for side effects from the vaccine, Polyakov says. But, he stresses, there is no suggestion that vaccination either before, during or after an IVF cycle impacts its effectiveness.

In fact, research published in May found no difference between the outcomes from the cycles of IVF before and after the vaccine in terms of number of eggs, quality of embryos or pregnancy rates.


So for the sake of clarity around symptoms, it may be smart to separate the timing of the vaccination and any IVF procedure or mammogram (unless you have a suspicious lump or are being treated for breast cancer). Otherwise, there is no need to delay.

“My advice to patients is to get whatever vaccination is available as soon as possible,” Polyakov says, pointing out that women who get COVID-19 in pregnancy are much more likely to end up in ICU, have a miscarriage or a stillborn baby. “Vaccination to me seems like a no-brainer.”

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Joanna Taylor

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