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What will it take to achieve herd immunity against COVID-19?

Information and guidance about COVID-19 care and vaccination continues to evolve. Please refer to the Centers for Disease Control and Prevention for the latest.

Herd immunity has been the dangling carrot, the saving grace that the world is waiting for as the end to the COVID-19 pandemic. We are now more than a year out from the first clusters of infection in China. There are currently more than 100 million cases worldwide and more than 400,000 deaths in the United States alone. 

The good news is, vaccination is underway. However, achieving enough herd immunity to effectively end the pandemic and go “back to normal” is a little more complicated than you might think. 

The short answer to ‘what will it take?’ is widespread vaccination. But before we get into the reasons for this, let’s examine what herd immunity really is and unpack some of the misunderstandings that often surround it. 

What is herd immunity, exactly?

The definition of herd immunity is “the resistance to the spread of an infectious disease within a population that is based on pre-existing immunity of a high proportion of individuals as a result of previous infection or vaccination.” 

Many people were already familiar with the term herd immunity prior to the pandemic thanks to decades of vaccination against former deadly diseases like measles, mumps, smallpox and polio. Thanks to modern science, these diseases are considered eliminated, meaning there is enough herd immunity to keep them at bay. A virus needs a host, and if all the hosts — or a vast majority of them — are immune to it, the virus can’t break into the herd. 

Herd immunity is also a term you might hear during flu season, but the threshold for herd immunity with the flu is much lower than what we’ll need against COVID-19.

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What percentage of the population needs to get vaccinated to reach herd immunity?

There is no magic number, and opinions vary. Still, most experts agree that for herd immunity to be realized, around 70-90 percent of the population must be immunized. 

Can we achieve herd immunity naturally without a vaccine? 

Technically, yes. But at what cost? By letting the virus “run its course” — without any precautions such as masks, physical distancing or lockdowns — the effects would be disastrous for our health, economy and hospital resources. 

We also don’t know for certain the long-term effects of COVID-19 on those who have been infected. Research suggests that some infected people, or “long-haulers” as they are more commonly known, could experience effects from the virus long after they have recovered. 

Getting to herd immunity through vaccination is the best path to protecting us all.

Once herd immunity is reached, do you still need the vaccine? 

Yes. Even if herd immunity is reached, routine vaccines are still required, depending on the disease. Over the years, anti-vaccine misinformation has led to clusters of infection all over the country for previously eliminated diseases like measles and pertussis. Herd immunity only works if everyone eligible receives a vaccine — but if there are low vaccination rates, the chance of outbreaks is much higher. 

We’re not yet sure what the long-term vaccination plan against COVID-19 will look like, but the most important thing now is that you get vaccinated as soon as possible.

When will everyone get the COVID-19 vaccine? 

Check the CDC’s most recent numbers to see how many people have been infected and vaccinated so far. State-by-state rollouts of the vaccine are happening with a tiered approach according to state and federal guidance, beginning with those at highest risk of facing severe COVID-19 illness. 

Consult the CDC’s website and your state health department resources to check your eligibility status and learn about vaccine distribution in your area. If you’re located in Texas, find out the latest in our area via the Department of State Health Services.

For more information on the vaccine, visit our dedicated COVID-19 vaccine page and download the MyBSWHealth app.

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About the author

Stephanie Kreiling, RN, BSN, MPH, CIC
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Stephanie Kreiling, RN, BSN, MPH, CIC, is the director of infection prevention and control for Baylor Scott & White Health.

What will it take to achieve herd immunity against COVID-19?