Pfizer vaccine: no evidence that it makes you infertile

Maybe you've seen some scary stuff on social media about the Pfizer vaccine affecting fertility? Here's why the scientists say it's all very misleading...

vaccine being given in woman's arm

We’ve been seeing lots of social-media posts suggesting that the Pfizer/BioNTech coronavirus vaccine contains something that can affect your fertility – and therefore you shouldn’t have it if you want to get pregnant, either now or in the future.

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We can see that these posts are causing a lot of concern, so we want to bring you the full scientific facts from the experts…

Can the Pfizer/BioNTech vaccine affect your fertility?

No, there is no evidence that the Pfizer/BioNTech vaccine causes fertility problems. And the claims being made on social media are “essentially fictitious”, according to virology professor Ian Jones at the University of Reading, quoted on the independent fact-checking site FullFact.

Why am I reading that the vaccine contains a protein that stops you making a healthy placenta?

The posts making their way around social media are incorrectly talking about a spike protein called syncytin-1. The false stories claim that the vaccine contains syncytin-1 and that if you have the vaccine, your body will produce an immune response that fights off syncytin-1. They claim this could make you infertile because you need syncytin-1 to make a healthy placenta.

Here’s how those posts are wrong:

  • The Pfizer vaccine does not contain syncytin-1.
  • The Pfizer vaccine works by giving your body’s cells ‘instructions’ to make a (harmless) spike protein that’s unique to Covid-19. Your body then recognises that this protein shouldn’t be there, destroys it and builds ‘fighter’ blood cells to attack it if it detects the Covid-19 spike protein in your cells again. (You can read more about how the vaccine works on the official US Centres for Disease Control and Prevention site). A small part of this spike protein resembles a small part of another protein – called syncytin-1 – which is vital in the formation of the placenta in pregnancy. But this similar part is so small, as biochemist Edward Niremberg explains, that your immune system is ‘extremely unlikely’ to confuse them with each other and then attack any syncytin-1 in your body. If it did, we would expect to see Covid-19 causing a significant amount of early pregnancy loss – and there’s no evidence of this.

Is it safe to have the Pfizer vaccine if I’m planning to conceive or want to get pregnant at some point?

Yes, there is no evidence that the vaccine affects fertility. If you are offered the vaccine (most likely at this stage because you are clinically extremely vulnerable or a frontline health or social-care worker), the most up-to-date advice (December 30 2020) from the UK’s medical officers is:

Those who are trying to become pregnant do not need to avoid pregnancy after vaccination
UK Chief Medical Officers

It’s also worth noting that saying that, although no specific data about the vaccine and human fertility has been gathered yet – because it’s not been specifically studied – there is some published data from animal studies.

The UK Information For Healthcare Professionals for the Pfizer vaccine says: “Animal studies do not indicate direct or indirect harmful effects with respect to reproductive toxicity” (Section 4.6) and “There were no vaccine-related effects [in animal studies] on female fertility, pregnancy, or embryo-foetal or offspring development” (Section 5.3).

Pics: Getty

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