The Parkland Center for Clinical Innovation (PCCI) said Dallas County reached the ‘herd immunity’ threshold of more than 80% of the population having been vaccinated or previously recovered from COVID-19 July 4.
Herd immunity is the indirect protection from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous infection,” according to the World Health Organization. PCCI’s calculations used to measure herd immunity track individual-level data for both vaccinations administered and COVID test results since the beginning of the pandemic. The model also calculates an overlap of about 28% of the vaccinated population of Dallas estimated to have had prior COVID-19 infection and recovered.
PCCI says the pace of vaccinations continues to lag, though, with 38% of the total population who completed their vaccination series and 47% of the total population with at least one dose (61% of adults and 80% of those over the age of 65 years) as of July 7.
“While this represents good progress, it is important that we understand the work is not over. We must continue to push for vaccinations so COVID and its variants can’t again take hold and diminish the progress we’ve made,” PCCI CEO Steve Miff said in a statement.
Miff said the spread of the highly infectious delta variant adds to the importance of getting vaccinated, particularly as the level of immunity against that strain offered from previous infection remains unclear.
“ While previous infections and partial vaccinations do provide a level of protection, all evidence suggests that full vaccinations are the most effective way to stay safe against the delta variant,” he said.
He said the delta variant makes up about 25% of COVID-19 cases locally but could make up up to 75% of the cases in two-to-four weeks.
“The significantly higher viral loads and more infectious nature of the Delta variant could put the herd immunity target as high as 88 percent to suppress infection spikes when the Delta variant becomes the dominant variant in a few weeks’ time,” he continued.