Coronavirus Herd Immunity Could Be Reached By Spring: UAB

BIRMINGHAM, AL — Almost a year after the first known case of COVID-19 was diagnosed in Alabama, researchers at the University of Alabama at Birmingham say the U.S. could reach herd immunity to the virus by late spring.

UAB experts say at least 3.5 million people would have to have been infected with the virus or vaccinated in Alabama for the state to reach herd immunity. Thus far, the Alabama Department of Public Health has confirmed just under 500,000 cases of the virus, and about 213,000 people have been fully vaccinated. But those numbers do not necessarily mean the state is that far from herd immunity, according to Dr. Suzanne Judd, Ph.D., an epidemiologist in the School of Public Health at UAB.

Based on the number of vaccinations that have already been administered, as well as findings from a recent study by Columbia University, Judd estimates the nation may reach herd immunity by May. The study by Columbia suggests that, as of the end of January, more than a third of the U.S. population had already been infected with coronavirus.

"Three factors determine how quickly Alabama can get to 3.5 million people with immunity: number of people with a positive test, number of people who were infected with COVID but never had a positive test, and the number of people vaccinated," Judd said. "We have great data to know how many people tested positive and how many people have been vaccinated. From there, we can estimate how many people have immunity but never received a vaccine and never had a positive test based on studies that have tested immunity in blood. We are able to put these numbers together and come up with the estimate of when we will reach herd immunity, which is May of this year."

Reaching herd immunity does not mean the virus will be eradicated, Judd said.

"I think that COVID-19 is going to be endemic in the United States," Judd said. "It is going to be like the seasonal flu, something we have to tolerate regularly. There will be isolated outbreaks, and they will likely occur in populations with lower immunity. This means that, just like the flu, a strong vaccination campaign will be needed to keep people out of the hospital."

Judd also said another positive trend that shows the reduction of the severity of COVID-19 cases is the decrease in the number of hospitalizations and deaths.

"We are seeing sharp declines in the hospitalization ratio in the last month and a half, likely driven by monoclonal antibody therapy, but possibly also driven by the vaccine," Judd said. "If people are vaccinated and still become infected, the case may be milder than it would have been if they were not vaccinated, which leads to lower hospitalizations."

Judd said reaching more communities with the vaccine is key.

"We need to get consistent vaccine administration to lots of different populations" Judd said. "We cannot leave people behind. We have to make sure the vaccine is getting into all communities to get that base level of immunity to stop the virus from spreading."