Vaccines Do Not Cause the Kind of Sterility Anti-Vaccine Activists Tell You About

When communicating complex scientific topics to the public, we often face several hurdles to get the message across. One of the biggest hurdles is misunderstanding technical concepts or misunderstanding technical terms. Scientists and science communicators often forget that most people are not like them. Most people did not graduate from college with degrees in science. Only . So we must be clear in our communication, so that most people understand what we are trying to say.

History of Vaccines has a of terms now under review to make sure the reading comprehension level is not too high. Among those terms, we will add “Sterilizing Immunity” soon, but we want to make clear what this term means. The term “sterile” means “unable to reproduce.” For example, a spayed or neutered cat is sterile because it cannot have kittens. A person who develops mumps disease can have a complication called “orchitis.” This means the virus causes swelling of one or two testicles. Those people have , and an increased risk of “subfertility” (or ).

Something that is sterile also means “free from microorganisms,” as in a sterile environment in an operating room, or the sterile environment on a planet where life cannot survive. When we talk about “sterilizing immunity” in talking about vaccines, we mean an immune system so strong that an invading microbe cannot survive in the body. To fully understand this concept further, we need to talk about the stages from exposure to recovery of a disease.

Exposure is when a person is exposed to a microbe. This happens thousands of times a day, as the world is full of microbes. Some microbes are better than others at landing on us and colonizing us. “Colonization” is when the microbe establishes itself in or on our body without causing disease. Infection is when the microbe begins to multiply, which causes damage to the surrounding cells, triggering disease.

Not all infections lead to noticeable disease, by the way. If the immune system is quick enough to react to an infection, the infection will end with the person not feeling any symptoms of the disease. (We call this “subclinical” disease, meaning the person doesn’t feel sick and does not seek medical care.) However, there is a high probability that the person will feel the infection in some circumstances. First, if the person’s immune system is slow to react to the infection. Or if the microbe is quick to multiply and cause disease. (We call this “clinical” disease.)

As a result, the purpose of all vaccines has always been to prevent disease, not infection. If a vaccine can prevent infection, great. If not, preventing disease becomes the next best thing, and the true measure of vaccine “effectiveness” you might hear about in the news. Vaccines are not a magical force field that keeps microbes from landing on you. They help the immune system be ready and strong enough to respond to an infection as fast as possible.

Because of the way the human body works, the way microbes behave when they land on us, and the way vaccines trigger immune responses, proving “sterilizing immunity” from vaccines is difficult. While we can test a person for the presence of a virus or bacteria, or for the immune response to an infection (through testing for “antibodies”) there is no way to prove a negative. It is impossible to prove the absence of a virus, bacteria, or antibodies. There is no way to prove that the lack of microbes that cause disease is because of a strong immune system. Similarly, we don’t know if the lack of microbes is because the microbes did not survive colonization for some reason.

So why this long explanation of “sterilizing immunity”?

Because anti-vaccine activists have taken the term and used it to scare people away from vaccinating. They say vaccines will “sterilize” people who take them. They scare people away from the HPV vaccine by claiming the vaccine will make people sterile. . Other anti-vaccine activists will say the mRNA technology used in the new COVID vaccines also cause sterility. . What seems to have happened is that an anti-vaccine group, or two, took the term “sterilizing immunity” and, not knowing what it really meant, decided that it meant a person taking a vaccine traded in their ability to have children for immunity against a disease. .

There is another fact anti-vaccine activists have twisted and used to misinform. In places around the world where vaccines have been introduced, the fertility rate (number of live births per woman of childbearing age) has declined. Families in those places are having fewer children, but it is not because of vaccines alone. The arrival of vaccines also meant the . Farmers who got access to machinery no longer needed large families to work the farms. People with . Others learned about birth control and chose the size of their families. And, yes, , there is no need to have younger children to replace them.

So, no, there is no credible evidence of a conspiracy to depopulate the planet. If anything, . Like most things anti-vaccine, it’s all a misunderstanding... And probably an intentional one.

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