What Is Natural Immunity?

Medically Reviewed by Sabrina Felson, MD on March 08, 2024
6 min read

Your immune system defends your body against infections and illnesses. It makes proteins called antibodies that counteract or kill germs, like viruses and bacteria. You get protection, or “immunity,” from a specific disease when your immune system makes an antibody for it.

Natural immunity happens after you get infected by a germ and your immune system responds by making antibodies to it. The infection could make you sick. But if you’re exposed to that germ in the future, your body’s defenses spot it and fight back with antibodies. This makes you less likely to get infected again.

Natural immunity to a disease can weaken over time, though. How quickly or slowly this happens depends on the disease.

For example, if someone gets natural immunity from a COVID-19 infection, the immunity may fade after 3 months. On the other hand, a child who gets measles is unlikely to ever catch it again.

Here’s a look at the different types of immunity, including the differences between natural and vaccine-induced immunity, and how they compare against COVID-19.

Vaccines can protect your immune system against diseases without making you sick.

They safely boost your immunity by using an important protein from the virus or bacteria--just a piece of it so that it is unable to replicate in the host. Even though they can bring on side effects, they rarely make someone seriously ill.

Many vaccines can cause side effects like:

But side effects like these don’t mean you’re sick or that you got an infection.

Severe vaccine side effects are rare. In most cases, the benefits of getting vaccinated against a disease far outweigh the risks.

While it’s true that natural active immunity can make you immune to a disease after just a single case of infection, there is a downside: You have to get sick. And many illnesses can cause serious health issues that can affect you, sometimes for life.

For example, in some people, chickenpox can cause lung infections (pneumonia), blood infections (sepsis), and swelling of the brain (encephalitis). Before a vaccine was developed, this common childhood illness resulted in 10,000 hospitalizations every year.

You can avoid risks like these by getting all the vaccines your doctor recommends.

Vaccine-induced immunity and natural immunity are both types of active immunity. That’s the medical term for when you’re exposed to something that spurs your immune system to make antibodies to a disease.

Depending on the disease, both naturally acquired natural immunity and the vaccine-induced type can last for a long time.

This is the other main type of immunity. Instead of your body making antibodies, you get passive immunity by receiving antibodies from another source.

This can happen in a couple of ways. A newborn gets passive immunity from their mother through the placenta, a structure in the womb that gives the baby oxygen and nutrients. You can also get passive immunity from treatments that have antibodies in them. You might need this type of treatment right away if a certain disease makes you sick. Doctors don’t recommend it for routine use.

Passive immunity provides germ-fighting power right away, whereas it can take weeks for you to build up active immunity. But in general, passive immunity doesn’t last as long.

It’s when a contagious disease stops spreading easily because enough people in the community (or “herd”) have become immune to it. This can be because of natural active immunity, vaccine-induced immunity, or passive immunity.

Vaccines aim to safely create herd immunity against infectious diseases by limiting the number of people who can spread the infection. But lots of people need to get vaccinated to help protect those who can’t for medical or other reasons.

For example, before the vaccine for smallpox was available, the disease used to kill millions of a people each year. Today, mass vaccination has basically rid the world of smallpox.

Some people who haven’t gotten vaccinated against COVID-19 worry about the safety of the vaccines and say they’d prefer to get natural immunity. But there are several dangers to doing that.

If you’re not vaccinated, there’s a much bigger chance that the virus could make you seriously sick or kill you. There’s no way to know whether the disease will be mild or severe. You also risk spreading it to other people, including loved ones. What’s more, you may be twice as likely to get re-infected by the virus, compared to someone caught COVID-19 while fully vaccinated.

If you catch COVID-19, research suggests that the natural immunity you get from it makes another COVID infection unlikely for 90 days. Experts aren’t sure just how long that level of protection lasts, though. But even if you’ve had COVID, you can be infected again: A recent study showed that people who’d had it but weren’t vaccinated were more than twice as likely to get it again, compared to vaccinated people who got a breakthrough case.

Getting fully vaccinated also gives you months of immunity -- without making you sick from the coronavirus. The vaccines are safe and effective. Even though they become less effective over time, they can still help protect you from getting severely ill from a breakthrough infection.

None of the updated 2023-2024 COVID-19 vaccines is preferred over another and the CDC recommends the updated COVID-19 vaccines: Pfizer-BioNTech, Moderna, or Novavax, to protect against serious illness from COVID-19. 

The CDC also recommends everyone 6 months or older get an updated COVID-19 vaccine. Vaccination remains the best protection against COVID-19-related hospitalization and death. Vaccination also reduces your chance of suffering the effects of Long COVID, which can develop during or following acute infection and last for an extended duration. 

Receiving an updated 2023-2024 COVID-19 vaccine can restore and provide enhanced protection against the variants currently responsible for most infections and hospitalizations in the United States. 

Whether you call it “hybrid” or “super” immunity, these terms mean the same thing. Your body’s defenses may have gotten a short-term, “turbo-charged” boost if you caught COVID-19 and then got vaccinated. A small study also suggests you could get this type of boost from a breakthrough infection if you’ve already been vaccinated.

Lab research suggests that people with hybrid immunity make higher levels of virus-fighting antibodies than people who’ve been either vaccinated or infected. Their antibodies are also more potent than those in people who’ve only gotten their initial COVID-19 vaccines.

Don’t try to catch COVID-19, even if you’ve been vaccinated. There’s still a chance you could get sick and accidentally spread the virus to others. If you haven’t gotten vaccinated, you’re more likely to get severely ill, be hospitalized, or die from COVID-19.

Experts aren’t sure how long hybrid immunity lasts compared to getting only vaccinated or infected. Early research suggests the protection drops over time.

With infectious COVID-19 variants like Omicron going around, it’s important to get vaccinated and keep up to date with your booster shots once you’re eligible for them.