Do Covid Vaccines Cause Infertility or Miscarriage?

Covid-19 vaccine infertility and miscarriage claims still circulate online despite all scientific evidence to the contrary. Many experts strongly recommend Covid-19 vaccination during pregnancy, while some remain neutral or advise avoiding vaccination. However, so much evidence has now been obtained that Covid-19 vaccines are ‘safe’ that reservations have shifted toward actively encouraging vaccination, because Covid itself is now known to put pregnancy at risk.

Some Infertility and Miscarriage Claims—and Why They Are Wrong

A Study Shows That Covid Vaccine Accumulates in the Ovaries—False!

This claim comes from misinterpreting a study in which rats received a much higher vaccine dose than humans (1333 times higher). At ‘48 after injection’ (the source does not specify a unit), only 0.1% of the total dose accumulated in the animals' ovaries. Much more was found at the injection site: 53% after one hour and 25% after 48 hours (usually the arm in humans). The next most common location was the liver, which helps remove waste products from the blood (16% after 48 hours).

BioNTech and similar mRNA vaccines are delivered using an immune system-activating package of viral genetic material within a fat bubble (lipid nanoparticle). This leads some people to reason incorrectly that the vaccine accumulates in fatty tissue. The lipid nanoparticle's purpose is not to accumulate vaccine contents in fatty tissue, but to facilitate transport through the circulation and passage through cell membranes.

Follow-Up Data from Vaccinated People Show That Vaccines Cause Miscarriages—False!

A miscarriage at any point after vaccination does not establish that the vaccine caused it. More specifically, to show that vaccination causes miscarriage, miscarriage rates in a group of vaccinated pregnant women must be compared with those in an unvaccinated group. If there is no difference, miscarriage risk cannot be attributed to the vaccine. This is what studies have found.

One study found miscarriage rates among vaccinated people consistent with the expected general-population rate of 12.5%. Dr. Victoria Male, a reproductive immunology specialist at Imperial College London, says these reporting systems are very good at detecting vaccine adverse effects that are normally rare in the population

Menstrual cycle changes, miscarriages and heart problems are already common in the population, so care is needed when attributing these adverse events to vaccines. Seeing these conditions in the data is not concerning because they are expected whether or not people are vaccinated. Concern and immediate investigation would be warranted only if the data represented far more miscarriages than seen in unvaccinated people—but that is not currently the case.

Some people have also presented charts showing a substantial increase in the number of people submitting these reports compared with previous years for other vaccines and drugs. This has been used to imply that Covid vaccination is less safe. However, the increase does not tell us that.

Vaccines Can Attack the Placenta—No Evidence!

In a widely shared article, scientific researcher Micheal Yeadon, who has also made other misleading statements about Covid, claimed that the coronavirus spike protein in the Pfizer and Moderna vaccines resembles a protein called Syncytin-1 involved in forming the placenta. He speculated that this could cause antibodies against the virus to attack a developing pregnancy as well. Some experts believe this to be the original source of the belief that Covid vaccines could harm fertility.

In fact, Syncytin-1 and the coronavirus spike protein are as similar as any two randomly selected proteins. If the body were confused so easily, it would risk attacking its own organs every time it contracted an infection and developed antibodies.

To find an accurate answer to these claims, United States obstetrician Randy Morris followed patients undergoing IVF to see whether their chances of successful pregnancy differed according to vaccination status. Among the 143 people in Dr. Morris's study, vaccinated, unvaccinated and previously infected women had approximately equal chances of successful embryo implantation and an ongoing pregnancy.

Dr. Morris noted that people spreading these fears had not explained why they believed antibodies formed against a vaccine harmed fertility while the same antibodies formed through natural infection did not.

Covid Vaccination Reduces Sperm Count—Quite the Opposite!

On June 17, 2021, the respected medical journal JAMA published a study of sperm parameters before and after 2 COVID-19 mRNA vaccine doses, finding no decrease in any sperm parameter among vaccinated men. Because the vaccines contain mRNA rather than live virus, they are unlikely to affect sperm parameters. Although the results showed statistically significant ‘increases’ in all sperm parameters, the magnitude of change was within normal individual variation. The increase may also have reflected a longer period of abstinence before the second sample.