What does herd immunity from COVID-19 look like?

Last updated: May 10, 2021
Learn how getting vaccinated can help us reach herd immunity safely — and get back to living a normal life faster.

Thanks to three FDA-authorized vaccines for emergency use, 86 million Americans have been fully vaccinated against COVID-19 as of the third week of April. That includes more than 10 million Californians. That number will keep rising since all Californians age 16 and older became eligible for the vaccine on April 15. 

This is great news because it brings us closer to the one big thing experts say can help us stop the pandemic: herd immunity (sometimes called community immunity and population immunity). But there’s also been a lot of confusion about what exactly herd immunity is and what it takes to get there. To help make sense of it all, here are answers to some of the most common questions.

What is herd immunity anyway?

Herd immunity occurs when a large group of people in a community is protected from getting a disease. That could be because they have already had the disease, or because they’ve been vaccinated. Herd immunity makes it much harder for the disease to spread because fewer available hosts can carry and pass it along. 

How many people need to be immune to COVID-19 to reach herd immunity?

We don’t know yet. It varies with each disease. We know that herd immunity against measles requires about 95% of a community to be vaccinated. For polio, the number is about 80%. COVID-19 isn’t as spreadable as measles. But the vaccines for it aren’t quite as effective, either. Infectious disease experts such as Anthony Fauci, MD, think that about 85% of Americans will need to get the COVID-19 vaccine before we reach herd immunity.

Why is vaccination the best way to reach herd immunity?

Vaccination is a safer way to reach herd immunity than allowing more people to get sick with COVID-19. COVID-19 can be a very dangerous disease. You don’t know for sure how the virus will affect you. Even if you are very healthy, you can still get very sick or even die. If you have a mild case, you could spread the disease to family or friends, some of whom could get very ill. And in some cases, the symptoms of COVID can last much longer than the first infection. Learn more about long-term COVID-19.

Vaccination increases your immunity to COVID-19 without having to get sick with the disease. It may also prevent the spread and replication of the virus. We want to stop the spread, because replication can cause the virus to mutate or change into another form. Mutations could lead to more dangerous strains that are resistant to vaccines.

Why is it so important that essential workers get vaccinated?

Essential workers are at very high risk of getting COVID-19 because they spend their days in close contact with a lot of people. Teachers and first responders such as firefighters and police officers are in this group. So are people who work in grocery stores and for the U.S. Postal Service. If they do get infected, they may also get many others sick, even if they don’t have symptoms. For all these reasons, vaccinating essential workers can really help slow the spread of COVID-19.

What about social distancing and wearing a mask. Is that still important?

Yes, but the state of California has updated its guidance. Even if you’re fully vaccinated, you’ll still have to mask up and social distance. Some exceptions include when you are outdoors and around others who are also fully vaccinated. There are a couple of reasons for this:

  • A mask protects those around you. It’s true that the vaccines reduce the chance that you will get COVID-19. However, we still don’t know how well vaccines prevent you from passing the virus to someone else. Masks are a smart safety measure while we learn more.
  • A mask protects you. The COVID-19 vaccines themselves are very effective but not 100% effective. Plus, they might not be as effective against newer variants.

What are the biggest benefits of herd immunity?

Once enough people are vaccinated to reach herd immunity, we’ll probably be able to stop wearing masks and social distancing, at least in areas where there’s very little spread of COVID-19. You’ll be able to watch your kids play sports again or attend your cousin’s wedding. We’ll still have to keep our guards up: Even today, there are outbreaks of well-controlled diseases, like measles. These outbreaks usually happen when not enough people in a community are vaccinated.  It also helps protect those who can’t get the vaccine because they are too young, for instance.

While we’re waiting for herd immunity to become a reality, there are many things you can do that feel like “normal” life. A big one: You can hang out in small groups with other fully vaccinated people indoors without masks or social distancing. It will also be much safer to eat indoors at a restaurant or go to the gym. Sure, it’s not quite back to where we were pre-COVID-19, but it’s a wonderful start.


The information in this story is accurate as of press time and posting. To limit the spread of the coronavirus, it’s important to continue practicing social distancing (keeping at least 6 feet away from people outside your household) and washing your hands frequently. You should also be appropriately mask per CDC guidelines. Because the situation surrounding COVID-19 continues to evolve, we encourage readers to follow the news and recommendations for their own communities by using the resources from the CDC, WHO, their local public health department and our COVID-19 member site.

As of April 15, all Californians ages 16 and older are eligible for the COVID-19 vaccine.

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