For people who want to have a baby, false messages about fertility can be especially powerful. So I want to say upfront that the COVID-19 vaccine is safe for fertility.
[Body Stuff with Dr. Jen Gunter]
The data on this is clear. COVID-19 vaccination saves lives for everyone, especially pregnant people and their babies. But the fog of the pandemic has made it extra challenging to dispel the misinformation surrounding the COVID-19 vaccine.
So I want to address some of these worries by talking about how a vaccine becomes a vaccine in the first place. To show that each step of creating the vaccine is closely evaluated for safety.
One of the early stages of vaccine development involves exploratory research. In the case of the coronavirus that causes COVID-19, researchers already had years of knowledge and insight to work from. Scientists already knew a lot about other coronaviruses. And because of knowledge sharing, they were able to simply download the virus’s genetic code off a website. They were also able to take advantage of the advances made in mRNA vaccine technology, which you might have heard about.
While mRNA vaccines are new to the public, researchers have been studying and working with them for decades. I want to underscore this point. One worry about the vaccine is that it felt rushed. But while the COVID-19 vaccine was developed rapidly, its creation was based on decades of research.
Once the exploratory stage is finished, researchers move on to the preclinical stage, where testing is done in petri dishes or on animals. The goal of preclinical tests is to see if the vaccine truly works on the pathogen -- in this case, the virus that causes COVID-19 -- and also to test the safety of a vaccine. This is where researchers perform toxicity testing, using a dosage far greater than what they might use in humans to make sure it's safe. By testing on animals, they're able to see if vaccines have any impact on functions like the reproductive system. You might be surprised to learn that the chemical signaling that happens in a rat uterus is very similar to what happens in a human uterus. Here's what's important. Researchers don’t move on from the preclinical testing phase until they prove that the vaccine is unlikely to harm anyone. This is a rigorous process that goes through FDA approval.
Once the FDA approves, the next step is the clinical development or clinical trials, testing in humans, which is a three-phase process. Phase one starts with a small group of people, usually less than 100 very healthy adults. By phase three, researchers are working with thousands or even tens of thousands of people. Because of the urgency of COVID-19, researchers save time by overlapping these phases, using early data from each phase to design for the next. In other words, no steps were skipped. Now, it's true that clinical trials for the COVID-19 vaccines didn't include pregnant people, and that's not unusual. Pregnant people are currently part of a protected class that typically aren't included in testing new vaccines or new drugs. I completely understand the worries around this, but remember, testing in animals is a proven way to ensure vaccine safety. The preclinical data for the COVID-19 mRNA vaccine showed no impact on fertility in animals that would lead researchers to suspect there would be issues with humans.
Even after the vaccine has been approved by the FDA and made available to the public, there's still work to be done. These are called phase four trials, where researchers and regulatory agencies track how the public responds to the vaccine long-term. Monitoring side effects, collecting and analyzing data from a much wider population. And now we have even more data to reassure us about fertility.
After the COVID-19 vaccine was rolled out, there were reports online of people experiencing irregular periods or changes in their menstrual cycle. This, understandably, made people nervous about a potential effect on fertility or an unknown effect of the vaccine. We didn't have any data about irregular menstrual cycles from clinical trials to point to, and that is problematic. But given the rush to get the data, it would have been hard to collect because people would have had to track cycles before the vaccine. Differences people notice in their menstrual cycles are valid, and it's scary and uncertain to notice a change in our bodies. And because the endometrium, the lining of the uterus that sheds during a period, is part of our immune system, it is theoretically possible a vaccine could have a temporary effect in the same way a vaccine causes temporary swelling in the lymph nodes for some people or a temporary fever. Researchers responded to the concerns raised online and looked into data from almost 4,000 people who tracked their cycles using an app and compared data from the vaccinated group to those who didn't get vaccinated. On average, the menstrual cycles of people who were vaccinated varied in length by less than one day, which is interesting but not medically significant since normal menstrual cycles vary by up to seven days each cycle. The only group that was more likely to show a meaningful difference in their menstrual cycle length were those who received two doses of the vaccine in one cycle. Even then, what they observed was temporary. Their cycles went back to normal within three cycles.
And we've continued to gather data. We now see the importance of vaccination for those who are pregnant as the risk of mortality in pregnancy with COVID-19 is 1.6 percent. That's 22 times higher than the risk of mortality in pregnancy for those without COVID. And unvaccinated mothers and pregnant people who do get COVID-19 have a much higher chance of being admitted to the intensive care unit. We also now have data showing that infants from people vaccinated during pregnancy do have antibodies to help protect them from COVID-19.
If your goal is a healthy pregnancy, one of the best ways to achieve that is by getting vaccinated. And we can have confidence that the COVID-19 vaccines have been rigorously tested and are being closely followed.
