Children have been routinely vaccinated by medical professionals for more than 100 years. Now, with Pfizer's COVID-19 vaccine authorized in children 12 and up, scientists are once again reassuring the public of the shots' safety for younger generations.
COVID-19 vaccines introduced a new mRNA platform to immunization, but they work the same way other vaccines work to help the body create protection. On a cellular level, scientists say it's impossible for these vaccines to interfere with a person's own genetic blueprint. That means that like all other childhood immunizations, COVID-19 vaccines won't interfere with puberty, or future fertility.
"These particles cannot cause any long-term issues, such as autoimmune diseases or impacts on fertility or pregnancy," said Dr. Stacy De-Lin, a gynecologist and family planning specialist dedicated to preventing the spread of misinformation. "There is no link between the COVID-19 vaccines and fertility -- it's an urban legend."
Decades of research on the platforms used to create current COVID-19 vaccines have allowed experts to clearly understand what happens once the vaccine gets inside the human body – and say it cannot alter our own genetic makeup.
Unlike a traditional vaccine, which uses a weakened or killed virus to activate the body's defenses, these vaccines don't use the virus at all. Instead, vaccines from Pfizer and Moderna use small bits of genetic material called mRNA, which, like an instruction manual, tell your cells to make a protein normally found on the outside of the virus. This activates your immune system defense, protecting you if you are ever exposed to the virus in the future.
The single-shot Johnson & Johnson vaccine uses a similar strategy, delivering genetic material using a so-called viral vector.
None of these vaccines interfere with DNA -- the stuff that makes each person unique and is then passed on to the next generation. That's because DNA lives in your cells, in a special, protected location called the nucleus, and mRNA doesn't come close.
"Because the mRNA vaccines in no way enter the nucleus of the cell itself, they are in no way able to alter your DNA," De-Lin said.
Dr. Peter Hotez, a professor of pediatrics and molecular virology and the dean of the National School of Tropical Medicine, agrees there is no biological reason that mRNA could get into your DNA and interfere with adolescent development. "There's no plausible mechanism by which that could occur," Hotez said.
De-Lin also explained that after the mRNA vaccine stimulates the response from a person's immune system, the mRNA molecules from the vaccine itself exit the body within days.
There has been anecdotal talk of the vaccine temporarily impacting menstruation in some adult women, but there is no evidence that the vaccine could cause a change in menstruation long-term or could affect fertility.
In fact, in children, teens and adults, it is common for frequency and heaviness of periods to sometimes vary. "Women [and children] can have changes in their menstrual cycle and also have gotten the vaccine, that does not mean that one caused the other," Dr. Jennifer Ashton, ABC News's chief medical correspondent, said.
"As a biological compound, the vaccine does not have any hormonal properties that would make it possible for it to interfere with fertility, puberty, or the body's own hormonal processes," agreed Dr. Bracho-Sanchez, a primary care pediatrician and assistant professor of pediatrics at Columbia University Irving Medical Center in New York.
Studies in pregnant women back up the idea that COVID-19 vaccines don't impact fertility or hormone regulation, so if you are trying to get pregnant or want to get pregnant in the future, it's safe to get vaccinated, according to the Centers for Disease Control and Prevention.
"Thousands of women have given birth after both COVID infection as well as after vaccination, demonstrating no impact on fertility," De-Lin said. Plus, almost 5,000 individuals reported becoming pregnant post-vaccination through an active tracking program called V-Safe.
Bracho-Sanchez herself received the first dose of the vaccine while trying to conceive, and the second during her pregnancy. "The vaccine clearly did not prevent me from conceiving nor did I ever worry it would, because I thankfully understand the science," she said.
There is currently no evidence that any vaccines, including COVID-19 vaccines, cause fertility problems.