How Does COVID Immunity Work?

Early in the pandemic, information — and misinformation — circulated rapidly, from homemade sanitizer recipes to unproven remedies. Guidance evolved as scientists learned more.

So much has changed, in such a short time. We’re still living with COVID-19 — and people are still dying of it. But the world has opened back up. And with a few notable exceptions, we’re back to business as usual. Today’s ‘more normal’ life reflects a mix of protections — immunity from prior infection, vaccination or both — plus better treatments.

But what exactly does “COVID immunity” mean? Is being vaccinated the same thing as being immune? And what about people who are immunocompromised?

We asked family medicine specialist Neha Vyas, MD, to help us answer some of the most common questions about COVID immunity.

Can you be immune to COVID-19?

Given the sheer volume of people who became sick with or died of COVID-19 in the early days of the pandemic, you might think that all active healthcare workers and first responders got sick. And you’d be mostly right. Mostly.

While their numbers are small, to be sure, there are people out there who — despite being exposed to COVID-19 regularly for years — have never contracted the virus. And some of those people have weak immune systems!

It raises the question: Is it possible that some people have a genetic mutation that makes them immune, or resistant, to COVID-19?

According to the Association of American Medical Colleges, scientists are working hard to find out.

It’s an interesting topic to study because recent research has demonstrated that genetics can make people more vulnerable to the virus. A 2022 study in Nature found that somewhere between 5% and 10% of critical pneumonia cases in children with COVID-19 could be explained by genetic mutations that impacted their immune systems.

Dr. Vyas explains that, if researchers are able to uncover a genetic mutation that makes certain individuals immune to COVID-19, that may one day translate into better protection for vulnerable people. But as of now, the answer is no, you can’t be immune to COVID-19, at least as far as we know.

How does COVID immunity work?

By now you’re probably starting to realize that COVID immunity is a more complicated subject than most people might realize. But let’s step out of the realm of the speculative and focus on what we know for sure. There are three kinds of COVID immunity we can talk about with certainty: vaccine immunity, natural immunity and hybrid immunity.

Vaccine immunity

While you may be familiar with the concept of vaccine immunity, it’s important to know that different conditions require different approaches to vaccination.

Vaccination is one tool many clinicians recommend to reduce the risk of severe illness. Protection builds over about two weeks. If you’re currently ill, clinicians generally advise waiting until isolation ends before getting a dose. Your doctor can help with timing.

Vaccine immunity, like natural immunity, is a gradual thing.

Disease-induced (natural) immunity

Recovering from COVID-19 provides some protection that can wane over time and varies by variant and individual. Many healthcare providers recommend vaccination after infection to broaden or extend protection — talk with your doctor about what’s right for you.

Hybrid immunity

Studies suggest that people with both prior infection and vaccination often have broader protection for a period of time. That doesn’t mean anyone should seek infection — risks remain, especially for vulnerable people.

Can you be exposed to COVID-19 and not get it?

Now that COVID-19 is endemic (vs. pandemic), it’s fair to say you (and most humans) have been exposed to the virus repeatedly. But there are plenty of people who’ve never gotten sick.

How do some manage to avoid contracting COVID-19 after being exposed? According to Dr. Vyas, your risk of becoming infected has a lot to do with the safety measures you were following when you were exposed.

“The more you followed COVID-19 safety guidelines, the lower your risk of exposure and illness will be,” she explains.

The questions Dr. Vyas asks when trying to determine a person’s risk of getting sick include:

• Have you been vaccinated? When? And how many times?
• Have you had COVID-19? How recently?
• Were you in an enclosed space? If so, how large was it and how many people were inside?
• How long were you exposed for?
• Were you or the person who was exposed wearing a mask at the time? (While we don’t see them nearly as often as we used to, masks remain one of the best ways to protect yourself against respiratory infections like COVID-19 and respiratory syncytial virus [RSV].)
• How frequently did you wash and/or sanitize your hands during the exposure period?

If you followed all the safety guidelines to the letter, your chances of infection are low. But, as Dr. Vyas is also quick to point out, nothing is guaranteed when it comes to infectious diseases.

“So many different things affect whether or not a person exposed to COVID-19 will become sick,” she continues. “In addition to taking safety measures, you also have to consider the state of your immune system and where in their infection timeframe the person who exposed you was.”

Are you immune to COVID-19 after getting the vaccine?

It’s a simple question with a complicated answer: Are you immune to COVID-19 after getting vaccinated?

Both vaccination and prior infection can provide protection that changes over time. Population-wide immunity wasn’t achieved, and COVID-19 now shows seasonal patterns in many places. Breakthrough infections can occur, but vaccination is intended to reduce the risk of severe outcomes.

COVID-19 may not be in the news as much as it used to be, but it still claims about a thousand lives a week in the United States. We know that the effectiveness of the COVID-19 vaccines we have goes down over time.

Additionally, each new COVID-19 vaccine is tailored, like the annual flu vaccine, to provide immunity against the most common variants circulating at the time. And the evidence suggests they’re working well. The only problem is that not enough people are getting them.

Be a good neighbor

Some people — newborns, those who are immunocompromised and older adults — are at higher risk. If you’ll be around someone vulnerable, consider steps that fit your situation:

• Postpone a visit when sick
• Improving ventilation
• Consider using a high-quality mask.

If you’re weighing vaccination, talk with your healthcare provider about your health, prior infection and timing.

“If you have any questions about your COVID immunity, have a conversation with your provider,” Dr. Vyas advises. “They want to be sure you're confident and comfortable with your decisions.”