All residents and employees of an affluent private Florida island community are being given tests to determine whether they have been exposed to the coronavirus and developed antibodies to it.

Everyone living and working on Fisher Island, off Miami Beach, is being tested for the antibodies through serological tests, according to a statement from the community.

"Fisher Island is funding the cost of the testing," which was procured from the University of Miami Health System, the statement said.

Fisher Island is a "private luxury community ... consistently ranked as one of the wealthiest zip codes in the U.S.," which also "boasts a beach club with one of the country's only truly private beaches" and a luxury hotel, according to the club's website. "The island is home to over 700 prominent families from more than 40 different countries."

"Luxurious" condominium units run from $2 million to more than $40 million, the site says.

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Fisher Island is promoting social distancing measures and encouraging the use of masks, and it has closed club amenities like golf courses and tennis courts, according to the statement.

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The tests are being administered to "further minimize spread on the densely populated island with half of the residents over the age of 60 and at high risk," the statement said.

Five to nine people within the island's ZIP code have tested positive for the coronavirus, according to the state Health Department.

"The simple blood prick antibody test is used to determine if someone has been exposed to COVID-19 and has developed antibodies to the infection. It is not to be confused with the much rarer nasopharyngeal swab which is the test that detects infection," the statement said.

The University of Miami Health System said in a statement that it "provided these tests in accordance with our clinical standards, which are designed to address the health needs of all the communities we serve, we understand it may have created the impression that certain communities would receive preferential treatment. That was not our intent."

"One of the first confirmed cases of coronavirus in Miami-Dade County was on Fisher Island, more than half of the population is over 60 and many residents were returning from the Northeast. These factors, at the time, were taken into consideration when the request was received," the statement said.

The antibody tests are not yet widely available, and only one kind has been approved by the Food and Drug Administration for an emergency use authorization.

The FDA said in a recent statement that more than 70 test developers have told the agency that they have serological tests available, but it warned that many of the developers are falsely claiming that their products have FDA approval or authorization.

Fisher Island spokeswoman Sissy DeMaria Koehne would not say whether the tests being used on Fisher Island are approved. Neither would a spokeswoman for the University of Miami Health System.

Another potential problem with the tests is that the body takes several days after having been infected to develop antibodies, meaning a test given too early could come back negative even if someone has the virus.

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And Dr. Robert Redfield, director of the Centers for Disease Control and Prevention, said Monday that antibodies to the coronavirus are not yet proven to provide protective immunity.

"I think that's going to take us, pretty much, through the next year to be able to understand what the protection is, and how long we can see that last will probably take years for that to happen," Redfield told NBC News.

Still, he said, the tests will likely be integral to reopening the country because they will likely determine who can safely go back to work.

"There's a hypothesis that there is going to be protective immunity. We think there is protective immunity, because we have examples in animal models to support that," Redfield said. "We're going to be getting real-life information as we move through the next 12 months to be able to reaffirm that."