Shelby County may be near 50% immunity
Nearly half of Memphis and Shelby County could be immune to COVID-19.
During March, the University of Memphis, in collaboration with local labs, tested 316 random Shelby County blood samples for antibodies to the novel coronavirus. The samples were also proportioned by zip code to roughly match Shelby County demographics.
The study found an estimated 51% of people have some sort of immunity to the virus whether it is from vaccination or previous infection. This is the second, monthly study on the issue — the U of M conducted another study of 300 blood samples in February.
The March data has a lower estimate of natural, infection-related immunity than the February version, but both suggest that natural immunity is much higher than the known infection rate.
That February snapshot found that only 27% of the population had antibodies to the virus. At that time, about 17.5% of the population had received at least one dose of a COVID-19 vaccine, bringing Shelby County to an estimated 43% immunity.
The March data has a lower estimate of natural, infection-related immunity than the February version, but both suggest that natural immunity is much higher than the known infection rate.
In March, 19% of the samples turned up evidence of natural infection. That number was the aforementioned 27% in February, showing there is a lot of variance in a 300-person sample. Known infections are at about 10% of the county’s population.
The study also showed about 30% of the population had antibodies related to the vaccine. As of Thursday, mid-april, 280,000 people had had at least one dose of a COVID-19 vaccine. That equates to about 30% of the county’s population.
Memphis and Shelby County have a goal of vaccinating 700,000 people. That would be about 75% of the county’s population. If Shelby County were to reach that level and it did not entirely overlap with everyone who had gotten the infection, the county would reach more than 80% immunity to the virus.
Experts disagree as to how much of the population needs to have immunity for herd immunity to be reached.
Roche Pharmaceuticals and the city of Memphis paid for the study. The samples came from American Esoteric Laboratories.