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How Many People Need to Be Vaccinated For COVID-19 to Be Eradicated?

Updated: Jan 28, 2021

From what we know about SARS-CoV-2, somewhere between 60 and 72 percent of a population needs to be immune to the virus for its spread to stop. That's without taking isolation measures into account.

The exact number will depend on how well the vaccine actually works. Trials on promising candidate vaccines by Pfizer and Moderna have determined an effectiveness of 90 and 94 percent respectively, with immunity taking two weeks to develop following recommended doses. Even with an incomplete course, trial data suggests the Pfizer vaccine will most likely provide some degree of immunity.

Based on those estimates, at least 7 out of 10 people would need to be fully vaccinated with the recommended two doses to be confident of widespread immunity.

Some experts estimate that immunising just two-thirds of a population could be enough to halt the pandemic disease and help protect whole communities or nations.

But there are a number of assumptions hiding behind this estimate, risking high expectations.

For example, if immunity is found to be brief, on the scale of months to even a year or so, coordinating a period where around three quarters of all people are immune could be made more difficult.

Then there is the question of whether clinical trials accurately represent the potential level of immunity we can achieve in a more diverse population. It also depends on how many people already have a degree of immunity through a previous infection. Given we are likely to be underestimating infection rates worldwide, this number is probably higher than current statistics indicate.

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