What is Herd Immunity, and How Does It Help to Protect the Population from COVID-19?

Medically Reviewed on 12/7/2021

Herd immunity and COVID-19

Herd immunity is important because it protects those people who are most susceptible to an illness. It also keeps the disease from spreading as easily. Herd immunity is an increasingly popular topic with the COIVD-19 pandemic bringing the concept front and center.

Epidemiologists estimate that 70% of the global population needs to be vaccinated in order to reach herd immunity for this disease. The Delta variant raised some doubts about this percentage, though, as breakthrough infections have increased. Now, the estimate for vaccinations to reach herd immunity may be higher.

Some medical professionals believe that we won’t reach herd immunity anytime soon. This is because of low vaccination rates paired with breakthrough COVID-19 cases caused by the Delta variant. As the Delta variant swept across the world, more people were hospitalized, and ICUs filled up. The Delta wave was worse than the first COVID-19 wave of sickness, making herd immunity more important than ever.

What does herd immunity mean?

The bottom line is that herd immunity means that the entire population is better protected against a particular disease. Herd immunity can be difficult to understand because its meaning varies from one disease to another. Total herd immunity depends on:

  • How contagious a disease is 
  • Partial immunity after recovering
  • Vaccine effectiveness at stopping transmission

Importance of herd immunity

There is a population of people with compromised immune systems that cannot receive a COVID-19 vaccine. At the same time, young children are not yet eligible to get vaccinated. When an overwhelming majority of the population is vaccinated, it protects this vulnerable population by preventing widespread sickness. When people who are immunocompromised interact with the general population, they’re less likely to come into contact with someone who is sick.

Measles is a great example of success with herd immunity. For measles, 90% of the population needed to be immune. In the case of measles, people could achieve immunity by surviving an infection or getting vaccinated. Measles immunity was successful until 2019 when a drop in vaccinations led to measles outbreaks.

COVID-19 is different than measles because of virus variants. It’s also easier to transmit from person to person, making it more contagious. This means that herd immunity may be more difficult to reach.

Natural infection vs. vaccination

Recovering from the COVID-19 infection does offer antibodies that can help fight off future infections. However, some people believe that natural immunity is the same as vaccinated immunity. This is one of the COVID-19 myths, and here’s why:

Reinfection is possible. Medical professionals are still studying how long natural immunity lasts. Even with COVID-19 antibodies, it’s still possible to get sick again. While you may not get as sick, you’re still contagious and can infect others who may not have immunity.

Vaccines offer an alternative immunity for those who haven’t yet contracted COVID-19 to have antibodies. Vaccines offer the benefit of immunity without the risk of serious illness or death that comes with a natural infection. Vaccines are effective at helping reach herd immunity, as proven by contagious diseases like:

Hurdles for COVID-19 herd immunity

Resistance to vaccinating. Many people don’t believe in the COVID-19 vaccine for religious reasons. Others are skeptical about the associated risks or believe that the idea of herd immunity is too good to be true. COVID-19 will continue to spread, though, as long as we don’t reach herd immunity, even with a large percentage of the population vaccinated.

Doubts about protection. The COVID-19 vaccines are still very new, even with rigorous testing before rollout. Experts are still researching how long the COVID-19 vaccine offers protection against infection. For example, the current vaccines may not work as well against variants of the virus.

The bottom line

Herd immunity is possible, but it won’t happen as quickly as most people think. COVID-19 is likely to linger for several more years with breakthrough infections. As more of the population recovers from the virus and gets vaccinated, though, immunity increases.

If you think you may have COVID-19 or have questions about getting the COVID-19 vaccination, talk to your doctor. They can help you weigh the pros and cons to decide what's the best treatment or vaccination option for you.


Bowel regularity means a bowel movement every day. See Answer
Medically Reviewed on 12/7/2021

American Medical Association: "What doctors wish patients knew about COVID-19 herd immunity."

John Hopkins Bloomberg School of Public Health: "Rethinking Herd Immunity and the Covid-19 Response End Game."

Mayo Clinic: "Herd immunity and COVID-19 (coronavirus): What you need to know."