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Wednesday 29 November 2023 Dublin: 4°C

FactCheck: No, Pfizer did not say unprotected sex should be avoided after the vaccine because of risk from 'genetic manipulation'

A false claim on social media suggests that a Pfizer document said vaccine recipients should not have unprotected sex for 28 days after receiving their second dose.

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A CLAIM SHARED widely on social media recently suggested that Pfizer said recipients of its Covid-19 vaccine should not have unprotected sex for 28 days after receiving their second dose.

The post states that a document from Pfizer says there is a “reproductive safety risk” after receiving the vaccine and “birth defects due to genetic manipulation”.

However, the claim is false and inaccurate on multiple grounds.

The Claim

The claim has been shared on social media as an image with text that suggests a Pfizer document said recipients of the vaccine should not have unprotected sex for a month after receiving their second dose because of “reproductive safety risk” and “birth defects due to genetic manipulation”.

The image text says: “Page 132 of Pfizer vaccine… basically says no unprotected sex up to 28 days after 2nd dose due to reproductive safety risk.. this is for males and females..births defects due to genetic manipulation [sic].”

The claim emerged on social media around 28 and 29 December and was shared on multiple social media platforms, including Facebook, Twitter, Instagram and Reddit.

One Irish Facebook page, for example,  shared the claim on 30 December in a post that has been shared 321 times and received 372 reactions and 214 comments.


The Evidence

The Pfizer/BioNTech vaccine was approved for use in Ireland on Christmas Eve, and the first vaccination administered in the country was delivered on 29 December.

The vaccine works by giving two doses a few weeks apart, and the claim on social media has suggested that Pfizer said people who receive the vaccine should not have unprotected sex for 28 days after receiving the second dose.

However, the document referenced in the post does not relate to the rollout of the vaccine as the post says.

Rather, it is a 146-page document outlining the protocol for the clinical trials of the Pfizer vaccine.

The trials took place to test the vaccine’s safety and efficacy before it was released.

The National Institutes of Health recommends that contraception requirements are in place for any clinical trial participants who take part in a trial in the US, such as the Pfizer trials, who engage in heterosexual intercourse, whether or not there is any risk posted by the study to a foetus.  

Women were eligible to participate in the trial for the Pfizer/BioNTech Covid-19 vaccine if they were not pregnant or breastfeeding and if they either did not have “childbearing potential”, or if they were using an “acceptable contraceptive method” for at least 28 days after they took their last dose of the vaccine trial. 

Men were also subject to eligibility requirements to participate in the trial.

“Male participants are eligible to participate if they agree to the following requirements during the intervention period and for at least 28 days after the last dose of study intervention, which corresponds to the time needed to eliminate reproductive safety risk of the study intervention(s),” the document outlined.

The requirements for male participants included that they refrained from donating sperm.

Additionally, they needed to either be abstinent from heterosexual intercourse with women that had childbearing potential, or agree to use a condom, and for women partners to use a “highly effective method of contraception”. 

The document outlines twelve different types of contraception considered to be effective, including oral hormonal contraception, intrauterine devices, condoms, and abstinence.

A series of false claims

There have been a number of widely-shared false claims on social media about the vaccine’s effects on fertility, pregnancy, and ‘genetic manipulation’.  

Claims that the Pfizer/BioNTech vaccine causes infertility in women have previously been factchecked by and other outlets, including AFP Fact Check and Snopes.

A claim that was shared widely on social media which suggested that the vaccine will lead to infertility in women by training the immune system to attack a protein involving in the formation of the placenta is incorrect.

Additionally, a spokesperson for Pfizer said that there is “no data to suggest that the Pfizer/BioNTech vaccine causes infertility”.

The suggestion that Covid-19 vaccines cause “genetic manipulation” is also false.

The Pfizer vaccine transfers RNA – ribonucleic acid – to cells in the body.

Human immune cells can then produce spike proteins that prompt the immune system to produce antibodies that work against the virus.

Vaccines using the RNA method do not change a person’s DNA, which means that claims that the vaccine causes genetic manipulation are inaccurate.

It is true that some health officials have advised the public to wait for a while before trying for a baby or receiving fertility treatments after receiving the Covid-19 vaccine.

This is because pregnant women were not included in clinical trials for the vaccine, so evidence is not yet available on how safe it would be for use during pregnancy.

In Ireland, chief executive of the Health Products Regulatory Authority (HPRA) Dr Lorraine Nolan said in December that because pregnant women had not been included in the initial trials, “[for] people that are maybe looking at having a baby or undergoing fertility treatments, the advice for the moment would be if you’re going to be vaccinated to wait a period of time and then to progress it”.

“Pregnancy is one of those areas where we will need further studies, there are some studies which will be concluded by the end of this year,” Dr Nolan said.

She said that data would become available early in 2021, after which “we may be able to look at pregnancy differently”.  

In the US, the Center for Disease Control and Prevention (CDC) has said that “based on how mRNA vaccines work, experts believe they are unlikely to pose a specific risk for people who are pregnant”.

“However, the actual risks of mRNA vaccines to the pregnant person and her fetus are unknown because these vaccines have not been studied in pregnant women.”

The Verdict

The image shared on social media does not show a document from Pfizer with guidance on the delivery of Covid-19 vaccines as it purports to.

Instead, the document is one with protocols for the clinical trials of the Pfizer vaccine.

It outlines certain criteria for eligibility in the trial, including ones that mitigated the involvement of people who are pregnant, could become pregnant, or could cause another person to become pregnant during the trial. 

Pfizer’s vaccine against Covid-19 does not genetically manipulate recipients of the vaccine. It uses mRNA technology which transfers RNA to humans to allow cells to learn how to fight off the virus if they come into contact with it, but it does not interfere with a person’s DNA.

As a result, we rate the claim that this image shows Pfizer saying vaccine recipients should not have unprotected sex for 28 days after their second dose: FALSE.

As per our verdict guide, this means: The claim is inaccurate. 


There is a lot of false news and scaremongering being spread in Ireland at the moment about coronavirus. Here are some practical ways for you to assess whether the messages that you’re seeing – especially on WhatsApp – are true or not. 


Look at where it’s coming from. Is it someone you know? Do they have a source for the information (e.g. the HSE website) or are they just saying that the information comes from someone they know? A lot of the false news being spread right now is from people claiming that messages from ‘a friend’ of theirs. Have a look yourself – do a quick Google search and see if the information is being reported elsewhere. 

Secondly, get the whole story, not just a headline. A lot of these messages have got vague information (“all the doctors at this hospital are panicking”) and don’t mention specific details. This is often – but not always a sign – that it may not be accurate. 

Finally, see how you feel after reading it. A lot of these false messages are designed to make people feel panicked. They’re deliberately manipulating your feelings to make you more likely to share it. If you feel panicked after reading something, check it out and see if it really is true.’s FactCheck is a signatory to the International Fact-Checking Network’s Code of Principles. You can read it here. For information on how FactCheck works, what the verdicts mean, and how you can take part, check out our Reader’s Guide here. You can read about the team of editors and reporters who work on the factchecks here

Have you gotten a message on WhatsApp or Facebook or Twitter about coronavirus that you’re not sure about and want us to check it out? Message or mail us and we’ll look into debunking it. WhatsApp: 085 221 4696 or Email: