If Most Floridians Have COVID-19 Antibodies, Why Is Miami-Dade's Case Positivity Rising?

The CDC reports that 58.4 percent of Floridians have COVID-19 antibodies, yet the seven-day case positivity has been rising since March.
The CDC reports that 58.4 percent of Floridians have COVID-19 antibodies, yet the seven-day case positivity has been rising since March. Photo by DBenitostock/Getty Images
It's been more than two years since the United States first instituted lockdowns to keep coronavirus cases to a minimum. Despite the efforts, new data from the U.S. Centers for Disease Control and Prevention (CDC) show that the majority of Floridians have contracted COVID-19.

In a recent data tracker report drawn from a nationwide survey, the CDC estimated the percentage of people in each state across the U.S. whose bodies contained COVID-19 antibodies — a figure known as "seroprevalence" — as of February 2022. The presence of antibodies indicates that a person has been infected with the virus at least once, and the data does not include instances of re-infection (i.e., when a person contracts the virus again).

According to the tracker, as of February, approximately 58.4 percent of Florida's population had already contracted COVID-19, up from the CDC's previous figure of 40.4 percent in January.

Florida had a smaller percentage of residents with antibodies than Alabama, Georgia, and South Carolina, which returned seroprevalence rates of 66 percent, 63.8 percent, and 64.5 percent, respectively.

When it comes to building herd immunity — i.e., when enough people have developed a resistance to the virus to limit its ability to spread — the presence of antibodies in nearly two-thirds of the population sounds promising. But Jackson Memorial Hospital's chief medical officer Dr. Hany Atallah tells New Times that the science is still inconclusive as to how much protection antibodies will afford people when it comes to the possibility of contracting and spreading the virus.

"The million-dollar question is: How much do antibodies really protect you?" Atallah explains. "We know for sure that vaccines protect well, and that without vaccines people are at higher risk for hospitalization."

Coronavirus cases in Miami-Dade have significantly dropped from their peak during the Omicron variant surge last December: from 52,428 between December 17 and December 23, 2021, to 6,170 between April 15 and April 21, 2022. Though it appears Miamians have largely moved on from dousing their hands in sanitizer and wearing facial coverings, Atallah warns that the pandemic is not over just because we think it is or so badly want it to be. People should still be wary and take precautions, he says, in light of the fact that the county's seven-day case-positivity rate — the percentage of positive PCR tests over the course of one week — has been on a steady rise after a decline that followed the Omicron surge.

In mid-March, the case-positivity rate in Miami-Dade County was 2 percent; it has steadily climbed each week since. The 11 percent figure reported last week prompted Miami-Dade County Mayor Daniella Levine Cava to post a statement on Twitter noting that the positivity rate had surpassed 10 percent and urging residents to stay up-to-date on their vaccinations and boosters.

According to the county's latest COVID-19 dashboard released Monday, the case-positivity rate is even higher now, at 13 percent. Approximately 131 more cases were reported each day last week than the daily case tallies from the week prior.

Though Miami-Dade boasts the highest vaccination rate in the state — 95 percent of the population 5 years of age and older have received one dose of a COVID-19 vaccine, and 85 percent are fully vaccinated — Dr. Atallah says Jackson Health Systems has seen a slight spike in what he calls "incidental" positive COVID-19 cases, in which a patient comes in for an unrelated medical issue only to test positive for COVID-19 when the hospital conducts a mandatory COVID-19 test.

Atallah estimates that the five main Jackson hospitals in Miami have seen an increase of five patients per week who come in with so-called incidental COVID-19. The good news is that the number of patients who are being admitted at Jackson hospitals specifically for COVID-19 has remained steady for the past several weeks, at about ten per week. (To put that into perspective, in December 2021, Jackson reported 252 COVID-positive patients.)

The numbers are low, but Atallah says he and other medical professionals still recommend that people exercise caution until COVID-19 goes the way of the flu and becomes a virus treated with annual vaccines.

"I don't think we’re totally out of the woods. We’ve seen surges in other parts of the world," he says. "We encourage people to gather outside during the summer months." 
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Joshua Ceballos is staff writer for Miami New Times. He is a Florida International University alum and a born-and-bred Miami boy.
Contact: Joshua Ceballos