‘You’re starting to see the precursor to herd immunity happen,’ MUSC scientist says

April 29, 2021
Sleeve of blue tshirt with vaccinated sticker
"I got my COVID-19 vaccine," the sticker says. Photo by Sarah Pack

As the MUSC COVID-19 Epidemiology Intelligence Project gives its weekly online update, the project’s leader has something important to say. “You're starting to see the precursor to herd immunity happen.”

The growth rate of cases for the Tri-county area dropped 25% compared with the previous week. There were about 860 cases in Berkeley, Charleston and Dorchester counties combined. The previous week, there were about 1,150 cases.

But Michael Sweat, Ph.D., a professor in the College of Medicine at the Medical University of South Carolina and director of the MUSC Center for Global Health, tempers the good news with a warning for people who are vulnerable to the virus.

“Even though the overall case rate is lower, the risk to those who have not been vaccinated or had a recent infection is currently extremely high as virtually all new infections are occurring in the shrinking group of those without immunity.” Sweat says. 

“Since early March, the number of cases has been going up and down around 20 cases a day per 100,000 people in the Charleston Tri-county area. You would expect it to be coming down more quickly with so many people getting vaccinated.”

Sweat thinks B.1.1.7., also known as the U.K. variant, may be the preventing that. “I'm suspicious that it's elevated the risk dramatically, which it has done everywhere else it’s become the dominant strain,” he said.

It’s the dominant variant in South Carolina, although it’s not clear how widespread it is because most coronavirus samples haven’t been checked for variants. But scientists do know that the U.K. variant spreads more easily and may make people sicker.

“If you were out there and saying, ‘Well, things are getting better. The rates are coming down, so what's the point of getting vaccinated?’ The reality is that no, you're in a pool of people that have very high risk,” Sweat said.

Under the latest Centers for Disease Control and Prevention guidelines, people who have been vaccinated can safely visit other vaccinated people inside without wearing a mask, visit unvaccinated friends or family in a single household without a mask, enjoy most outdoor activities mask-free and travel without COVID-19 testing. 

“There is a massive benefit to getting vaccinated. That really is the takeaway,” Sweat said.