When will we get back to business as usual? That’s the question that’s been on everyone’s mind since last March, when COVID-19 shut down most of the country.

The rollout of COVID-19 vaccines this year makes a return to normal more tangible in 2021, but pinpointing exactly when businesses can fully open and when people can safely return to the workplace is difficult.

To get there, we likely need to reach “herd immunity,” which, according to the Mayo Clinic, occurs when enough people gain immunity to an infectious disease that spreading it becomes unlikely.

Read Joe Cahill’s “A post-COVID pivot is possible, Chicago—but only if we act now.”

White House Chief Medical Adviser Dr. Anthony Fauci recently told the New York Times that COVID-19’s herd immunity range is likely 70 to 90 percent of the population.

The World Health Organization notes there are two ways to reach herd immunity: vaccination or a previous infection, though it’s unclear how long protective antibodies from a previous infection last. Some researchers estimate it’s at least six months, while others think it might be closer to 90 days.

Researchers at PHICOR (Public Health Informatics, Computational & Operations Research), headquartered at the City University of New York School of Public Health & Health Policy, ran a series of data-driven scenarios to estimate just when the United States might reach herd immunity.

This first scenario assumes that 1.7 million vaccine doses are administered daily, current mitigation efforts such as social distancing and masking continue into the summer, and the vaccines are 90 percent effective against the various strains of the coronavirus.


Herd immunity projection: 1.7 million daily doses

Source: PHICOR


By those measures, we could see 70 percent of the population reach COVID-19 herd immunity by early July, and by the end of the year a little more than 85 percent of the population could be immune.

The United States would reach herd immunity by vaccination alone in late October.

The CDC reports that on March 4 the seven-day average number of administered vaccine doses per day was 2 million.

So what happens if we can increase the number of vaccines administered each day to 3 million?

If that were to happen, 70 percent of the population could reach COVID-19 immunity by mid-May.


Herd immunity projection: 3 million daily doses

Source: PHICOR


As vaccinations roll out, it may be tempting to cease mitigation efforts like wearing a mask or social distancing. PHICOR’s data warns the consequences of that could be deadly.

At 1.7 million daily doses and no mitigation efforts being implemented, PHICOR estimates COVID-19 deaths would hit 911,415. That’s 221,554 additional COVID-19 deaths than the simulations that account for continuing mitigation efforts.

And while deaths would be up dramatically, we still wouldn’t hit herd immunity until early May, just a few weeks prior to when we would get there at 3 million daily vaccine doses being administered.


Herd immunity projection: 1.7 million daily doses with no mitigation

Source: PHICOR


Independent data scientist Youyang Gu conducted his own COVID-19 projections and came to a similar, though somewhat less optimistic, conclusion. His data shows the United States hitting 60 percent total immunity by June 1, but flattening out and not going above 64 percent for the rest of 2021. (His analysis argues that 60 percent could be enough to get back to “normal.”)

The University of Washington’s Institute for Health Metrics and Evaluation offers state-level COVID-19 infection projections. They too see COVID-19 declining as we head into summer.

Their data shows Illinois down to 4.5 infections for every 100,000 people by June 1. That would be the lowest infection rates since the first few days of the pandemic. That number was as high as 148 people in November.

Projected Illinois COVID-19 infection rate

Source: University of Washington’s Institute for Health Metrics and Evaluation

Notes: The PHICOR research was conducted in mid-February. It assumes 80 percent of the population eventually gets vaccinated and that protection from natural and vaccinated immunity persists throughout the duration of the simulation. It also assumes mitigation efforts slow COVID-19 variations that are more easily transmitted. PHICOR estimates how many people have been infected with COVID-19, but the actual figure is not known.

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