Some social media posts claim that unvaccinated people can experience Covid-19 vaccine side effects, particularly issues with fertility, simply by being in close proximity to people who have had a vaccine.
This is not true. The three types of vaccine developed to stop SARS-CoV-2, the virus which causes Covid-19, do not contain materials that could lead to “vaccine shedding”. There is also no evidence that vaccines affect fertility.
Fears about vaccine shedding, especially in live attenuated vaccines, are based on viral shedding, the process by which cells of the body release viral particles and could therefore, theoretically, increase the risk of infecting others.
Live attenuated vaccines, often referred to simply as live vaccines, contain whole bacteria or viruses which have been weakened (attenuated) so they can stimulate an immune response but do not actually cause the disease in healthy people.
There are three Covid-19 vaccines currently approved for use in the UK—Pfizer/BioNTech, AstraZeneca-Oxford and Moderna. None of them use a live version of SARS-CoV-2, the virus that causes Covid-19.
Professor Andrew Pollard, director of the Oxford Vaccine Group, told Full Fact: “I can’t think of any biologically plausible mechanism for shedding of components of any of the licensed Covid-19 vaccines after immunisation.”
Former chair of the BMA’s Public Health Medicine Committee Dr Peter English, a retired consultant specialising in communicable disease control, told us: “The mRNA vaccines [Pfizer/BioNTech, Moderna] do not contain anything that replicates and could possibly infect anyone else.
“It’s absolutely ridiculous to suggest that there could be any shedding of anything from someone who’s had one of those vaccines.”
Dr English, a former editor of Vaccines in Practice magazine, added: “The other type of vaccine used in Covid-19 is the vector vaccine [Oxford-AstraZeneca], and there I can see that people might be concerned about people being infectious with the vector virus.
“But those viruses are replication deficient… which means the [scientists] can grow them in a culture by adding an additive, which the viruses need to replicate but doesn’t exist in the human body.
“Once they stick them in the human body they can’t actually produce more copies of themselves. All they can do is produce copies of the spike protein, so they can’t be passed on to anyone else either.
“The suggestion that anybody could be infected with the vaccine virus by being in contact with someone who’s been vaccinated is pure misinformation at best, and disinformation at worst.”
There is a third type of vaccine, known as antigen vaccines, none of which have yet been approved for use in the UK. Similarly to the mRNA vaccine, Dr English said, there is nothing in these vaccines “that could possibly be shed or passed on”.
One of the social media posts claims vaccine shedding from the Covid-19 vaccine can cause “bleeding, bruising, spontaneous periods and miscarriages” while another warns of “anecdotal” evidence that women are reporting “miscarriage, suddenly bleeding while pregnant, heavy periods and irregular cycles” after being in contact with people who have been vaccinated. We can find no confirmed reports of this. At the time of writing, pregnant women in the UK are being offered the Moderna and Pfizer vaccinations after evidence from the US showed there were no specific safety concerns. Public Health England says that it “still advises that pregnant women should discuss the risks and benefits of vaccination with their clinician.”