Will the Covid Vaccine Make You Infertile?

One-quarter of young women in the UK would decline the Covid-19 vaccine because they are concerned about infertility. Is there a reason to be worried? Let's find out.

Will the Covid Vaccine Make You Infertile?

I have to be honest here. Before I got the covid-19 vaccine, I was sceptical about possible complications. Those were fears based on emotions, not information. Nevertheless, I found most of my family, friends and colleagues in the same situation.

My biggest fear was that it could make me or my future wife somehow sterile.

How could the Vaccine possibly make you infertile?

Antibodies are little proteins produced by your body's immune system when it detects harmful substances. These antibodies then bind these harmful substances, so your immune system can get rid of the invader. Covid-19 makes a spike protein and our body's natural response is to react with a fitting antibody. There is a similarity between the Spike Protein, that Covid-19 codes and Syncytin-1, a human protein important for placental development.

Fig. 1 Placenta

The main concern is now that antibodies against the Covid-19 spike protein would not just attack Covid-19, but also the placenta (i.e., an organ that develops in the uterus during pregnancy). This is called the cross-reactivity of antibodies.

Fig. 2 The same antibody reacts against two different proteins (called cross-reactivity)

Yet, these proteins have significant structural differences. The spike protein is bigger with 1,273 amino acids, while syncytin-1 has 538 amino acids.

Fig. 3 Comparison between the spike protein and syncytin-1

Furthermore, there was only about a 7% overlap in an alignment search between the spike protein and syncytin-1.

Fig. 4 Homology overlap between the spike protein and syncytin-1 (syncytin-1 is red and matches with spike protein are red underneath) 

Still, there is a chance that the antibodies could attack both proteins because the 3D structure depends on way more than just the size and similarity of the two proteins. That's why Akiko Iwasaki at Yale University tested the cross-reactivity of these antibodies in her laboratory.

The result:

Iwasaki and her team compared the coronavirus spike protein and syncytin-1, finding "very, very little overlap." When examining the spike protein's reactivity with syncytin-1, they found none.

That's good news because it means that your placenta is not in any danger after receiving the vaccine :). Antibodies against the Covid-19 spike protein will not attack the placenta.

In addition to that, we have data that showed that the miscarriage rate was the same between vaccine groups and placebo groups during vaccine trials.

Can Covid-19 make you infertile?

How does Covid-19 work?

At the host cell surface, SARS-CoV-2 binds angiotensin-converting enzyme 2 (ACE-2) to gain entry. The Spike protein binds ACE-2, leading to a conformational change that allows for viral entry. ACE-2 is highly expressed in type II alveolar cells within your lungs. This is why many infected people experience a cough or pneumonia after infection.

Fig. 5 Covid-19 gaining entry into the host cell via ACE-2

However, many other tissues within your body also express ACE-2 and are therefore a possible entry for the virus. Examples include the small intestine, kidney, but also your gallbladder and testes.

Fig. 6 ACE-2 expression within our body

ACE-2 expression in Sertoli cells

If you take a closer look, you will find that mostly Sertoli cells within your testes express ACE-2. Sertoli cells are important for the regulation of spermatogenesis (i.e., development of sperm cells), as well as for providing protection and nourishment for developing spermatocytes. They express ACE-2 in high amounts, making it possible for Covid-19 to enter and hijack these cells. Does this mean that Covid-19 will make you infertile? Probably not, at least there is not much evidence for this right now.

Fig. 7 Mostly Sertoli cells express ACE-2 within your testes

However, I found a single case report which showed a decline in long-term male fertility.

The conclusion of the case report:

Coronavirus disease 2019 (COVID-19) can impair male fertility with alterations in sperm morphology and DNA integrity could be a major post-COVID-19 complication in men.

You shouldn't worry about this result too much, since this is just a single case report.

Fig. 8 (A) Normozoospermia with an excellent sperm count, motility and normal morphology in a man before acquiring COVID-19. (B) Oligo-astheno-teratozoopsermia with decreased sperm count, motility and normal morphology in man after acquiring COVID-19

In summary:

If you want to be on the safe side for fertility it looks like it is smarter right now to get the vaccine. Both Covid-19 and the Covid-19 vaccines are highly unlikely to make you infertile. I hope you will all stay happy and healthy.

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  1. 24, F. (2021, May 14). Fertility fears, fueled by misinformation, harm US vaccine uptake. France 24. https://www.france24.com/en/live-news/20210514-fertility-fears-fueled-by-misinformation-harm-us-vaccine-uptake
  2. Zauche, L. H., Wallace, B., Smoots, A. N., Olson, C. K., Oduyebo, T., Kim, S. Y., Peterson, E. E., Ju, J., Beauregard, J., Wilcox, A. J., Rose, C. E., Meaney-Delman, D., & Ellington, S. R. (2021). Receipt of mRNA COVID-19 vaccines preconception and during pregnancy and risk of self-reported spontaneous abortions, CDC v-safe COVID-19 Vaccine Pregnancy Registry 2020-21. Research square, rs.3.rs-798175. https://doi.org/10.21203/rs.3.rs-798175/v1
  3. Cha, A. E. (2021, February 22). False claims tying coronavirus vaccines to infertility drive doubts among women of childbearing age. Washington Post. https://www.washingtonpost.com/health/2021/02/22/women-vaccine-infertility-disinformation/
  4. Male reproductive organs. (2021, May 16). AMBOSS. https://www.amboss.com/us/knowledge/Male_reproductive_organs
  5. Mannur, S., Jabeen, T., Khader, M. A., & Rao, L. (2021). POST-COVID-19 ASSOCIATED DECLINE IN LONG-TERM MALE FERTILITY AND EMBRYO QUALITY DURING ASSISTED REPRODUCTIVE TECHNOLOGY. QJM: monthly journal of the Association of Physicians, hcab019. Advance online publication. https://doi.org/10.1093/qjmed/hcab019

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