An epidemiologist at the University of Alabama at Birmingham predicts that the country and Alabama could reach herd immunity against COVID-19 as early as May or June.
“We are approaching herd immunity, thanks to the vaccine, as well as new scientific data that show us that more people have had COVID than tested,” said Susanna Judd, a doctor of epidemiology at UAB.
Judd said her calculations were based on the current rate of COVID-1
Herd immunity occurs when the virus cannot spread through an uncontrolled population because enough members of the population have some kind of immunity to either a vaccine or antibodies if they have had the disease and have recovered.
Scientists already know how many people have been vaccinated against COVID and how many people have tested positive for the disease. But there are a huge and unknown number of people who have received the virus and have never been tested.
If this number is high enough, the spread of the disease could drop dramatically in the coming months.
“The current forecast is that we will see [herd immunity] “Sometime in late spring, early summer in Alabama,” Judd said. “Sometime between May and June is likely, but it depends on many factors.”
Judd said new research in Columbia, Johns Hopkins University and UAB suggests that many more people may have already had the disease than we thought. According to New York, a study shows a nearly 10 to 1 ratio of people who currently have antibodies to people who have tested positive for the virus.
Judd said this was less surprising, as New York was badly affected by the virus at the start of the pandemic, when it was much harder to test for COVID. She said the ratio at UAB is closer to 5 to 1. Her prognosis, in an attempt to be conservative and not overdo it, suggests that there are three people who actually had COVID in Alabama for each positive test.
“The more people have immunity, the less the virus will spread, the safer it will be to interact with each other again,” Judd said.
Estimates vary depending on how many of the population need to be immunized to truly disrupt the spread of the virus, but Judd said her calculations are based on a threshold for immunity in 72% of the population.
“There is no magic number that is herd immunity,” Judd said. “Every virus, every bacterium is different and they mutate at regular intervals, so that number can move. But scientists are currently photographing about 72% of the population with immunity, so we hope to see that soon. “
For Alabama, Judd said that means 3.5 million people need to be vaccinated or infected. Current statistics show that 12.5% of the Alabama population has received at least one COVID dose of vaccine, and another 10% have tested positive for the virus.
As of Friday, Alabama reported 491,849 positive tests. Assuming a ratio of 3 to 1, this would mean that almost 1.5 million Alabama already had COVID. If the 5 to 1 ratio turns out to be true, it would be equal to more than 2.4 million people who have already been infected, bringing the state closer to that threshold of an immune herd.
Alabama’s public health officer, Dr. Scott Harris, said he was familiar with Judd’s work and said she had done a “huge job,” predicting herd immunity for Alabama.
“Dr. Judd is a great researcher, so I think what she has put together has been very intriguing and makes a lot of sense,” Harris said on Thursday.
Still, Harris said there are many unknowns about herd immunity, including how many Alabama may have already received COVID but never been tested.
“Just over 10% of our staff we know is positive and infected,” Harris said. “But certainly the percentage that has antibodies on board is much higher than that.”
Mutations can also be key to whether herd immunity persists, she said, or if booster vaccines are needed.
“It really depends on how the virus mutates,” she said. “There are some mutations that will be completely covered by the immune response that the body has already developed. There are other mutations that can escape the immune system and require a booster of the vaccine or actually lead to reinfection.
“So the options are something we have to watch very closely.”
Judd said the Alabama still shouldn’t leave their guard or start leaving their masks at home.
“We will not understand that we have herd immunity, there is no magic, we are suddenly 72% and we are safe,” Judd said. “The things we will monitor are the number of cases per week, we will continue to monitor this very closely. And as long as it moves down and stays below about 10 or 5 [cases] per 100,000 and we have decent tests in the state, then we’ll know it’s safe to get people back together. “