Worries that vaccines will affect fertility are a common trope in anti-vaccine rhetoric and are frequently employed to scare people out of getting vaccinated. They describe in lurid detail how an immunization is going to destroy a patient’s fertility. Take this example from a social media post I recently ran across:
Paints a scary picture, doesn’t it? Especially if you’re a clinician in a litigious society like the United States. It’s a patently false claim, but frightening if you don’t understand the argument or the reasons why it is untrue. So let’s take a look.
This argument isn’t new. In fact, claims that vaccines are sterility agents instead of preventive medicine have been used in anti-vaccine campaigns around the world, especially in middle-income and developing countries. And these misinformation campaigns result in devastating consequences.
In recent years this claim was repurposed and specifically used to target the Human Papillomavirus (HPV) vaccine, saying it would cause premature ovarian failure (POF) and thus destroy the recipient’s ability to conceive later in life. The HPV vaccination is most effective in pre-adolescent people who haven’t yet encountered any HPV viruses, but one very effective way to scare parents out of agreeing to immunize is to claim they are harming their child (and hypothetical grandchildren) .
Although infertility is not a known side effect of HPV vaccination, these concerns resulted in the development of huge research studies to assess for any possible connection, no matter how rare it might be. This level of scrutiny is typical for how vaccines are monitored. With the results of these studies we have a clear answer: there is absolutely no increased risk of POF due to HPV vaccination [4,5,6]. The exhaustive, nearly-900 page treatise on vaccine side effects from the Institute of Medicine does not list infertility as associated with any vaccine .
As NDs for Vaccines has covered previously, the HPV vaccine is actually associated with improved fertility , as you might expect for a vaccine that prevents cancers of the genitourinary tract. And it was so effective that the CDC removed a dose of the vaccine from the schedule (if the first dose is administered before age 15). Remember that next time someone tells you it’s all about money for “Big Pharma.” Did “Big Pharma” complain about lost profits from reducing the doses in the schedule? No, because they don’t make enough on vaccines compared to selling medication for it to be worth their trouble. But that’s a topic for another day.
Given the success of fear mongering over fertility, it is of little surprise that this claim has once again shown up regarding the COVID-19 vaccines. I’ve seen several false arguments, ranging from cross-reactivity of immune response to spike protein and the protein syncytin-1 in the placenta (a claim thoroughly explained and debunked by the inimitable Edward Nirenberg here), to “vaccine nanoparticles concentrating in the ovaries will make them into spike protein factories” of which there is simply no evidence nor plausible mechanism. That claim seems to have stemmed from documents submitted to Japan’s vaccine licensing body in which researchers showed that, in rats, lipid nanoparticles could be found at sites other than where the injection was placed.
These lipid particles are not the same thing as the vaccine itself, and are very rapidly broken down. In fact, less than 0.1% were traceable to the ovaries in humans . Remember, these lipid molecules are so fragile they have to be stored at -80 degrees C, so it is expected that they degrade and are metabolized by the body very quickly. The dose of these particles is measured in millionths of a gram; in the rat study mentioned above, they gave rats 50 micrograms (that’s 50 millionths of a gram). Assuming an adult rat weighs about 350 grams, this is the rough equivalent of giving a 150 lb human 9700 micrograms of lipid particles, which is a dose between 100 and 300 times higher than in any mRNA vaccine.
Although these arguments typically focus on patients with ovaries and uteruses, I have seen some claims that the vaccine somehow negatively affects sperm. There is no evidence of this, and sperm counts/motility are preserved after immunization . However sperm quality is reduced by COVID-19 infection, and erectile dysfunction is a known complication of COVID [16,17].
Furthermore, COVID-19 infections do not appear to cause adverse pregnancy outcomes (e.g.; miscarriage) during early pregnancy, but pregnant patients are more likely to have severe illness if they contract the virus [10,11,12,13]. Contracting COVID-19 infection in late pregnancy does increase the chance that a baby will be born preterm or need time in the ICU . In Pfizer’s initial emergency use authorization documents, they reported 23 pregnancies during the trial, which included over 44000 participants, and there was a single miscarriage in the placebo group.
The most recent data available from the longer term monitoring of the initial trial population showed a total of 89 pregnancies during the study, 5 miscarriages in the placebo group, 3 in the vaccine group, and no cases of fetal demise or birth defects were encountered in either group . A large study of over 30000 pregnant individuals who received COVID-19 vaccines found no increased risk of misscarriage or preterm birth .
Large scale trials monitoring pregnancy outcomes are underway, but there is simply no compelling evidence that COVID vaccines cause any pregnancy issues. The evidence is so overwhelmingly in support of vaccinating against COVID-19 during pregnancy that the CDC, American College of Nurse Midwives, American College of Obstetricians and Gynecologists, American Academy of Pediatrics, Society of Maternal Fetal Medicine, Society of Obstetricians and Gynaecologists of Canada, and the Royal College of Obstetricians and Gynaecologists all agree that all pregnant and breastfeeding patients should receive the vaccine to protect themselves from severe illness (and provide protective antibodies to their babies!).
So we can see, based on the available evidence, that COVID-19 vaccination:
- Has no negative effect on fertility;
- Has no negative effect on pregnancy outcomes;
- Protects against severe disease, hospitalization and death, all of which are more common in pregnant patients, and which can cause stillbirth, preterm delivery, and increase the chances of NICU admission, and;
- Is recommended by the major midwifery, obstetrics, maternal-fetal medicine, and pediatric organizations (the experts in the field, and the ones most likely to take care of pregnant patients and their babies).
Finally, it is worth noting that it is extraordinarily hard to procreate if you die from a preventable disease, become sterile by orchitis after mumps exposure, miscarry due to rubella infection, or are infertile after cervical cancer, all of which can be avoided with immunization. These are real risks.
Anti-vaccine activists’ false claims are a menace to patient health and safety. Social media allows for the uncontrolled malignant spread of inaccurate information from a weaponized unreality. As clinicians, we must openly address and debunk these claims when encountered, while counseling our patients on the importance of immunization to prevent severe illness from COVID.
Simply put: there is no evidence that infertility is caused by COVID-19 immunizations, or any other immunization.
Specific thanks to Victoria Male, whose exhaustively-researched explainer on COVID vaccines and pregnancy assisted in locating the most up-to-date versions of several references used in this article.