By Stephanie Stahl

PHILADELPHIA (CBS) — Testing for COVID-19 continues to ramp up around the region but availability is spotty and not everyone is eligible. There are two kinds of testing — one checks to see if you have coronavirus and the other looks for antibodies that indicate past exposure.

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The latter is what the University of Pennsylvania is working on. Doctors say both tests will be a critical part of figuring out when it’s safe to lift restrictions.

CVS is opening nine new drive-thru locations for COVID-19 self-swab testing. Even with the growing availability, it’s still limited.

“The problem in our country is that we are completely inadequate with the number of tests that are available,” Penn researcher Scott Hensley said.

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Hensley is a virologist at the University of Pennsylvania, where they’ve developed a new antibody test for COVID-19.

“We are completing a number of studies to measure the seroprevalence within Philadelphia. That is how many people in Philadelphia have antibodies against this new virus,” Hensley said.

Different from diagnostic screenings that happen with swabs to detect active virus, antibody testing measures past exposure, but more than 100 tests have quickly flooded the market.

“Some of these tests are not very accurate so you need to be very careful,” Hensley said.

That’s because people who have antibodies after being exposed to COVID-19 are presumed to have some level of immunity, but that’s still being investigated.

“Although I’m very encouraged that most of us will develop antibodies, protective antibodies once exposed to this virus, we have to be very careful with not over-interpreting these tests,” Hensley said.

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Hensley says antibody testing will be a critical part of safely reopening communities and keeping people safe.

“The major value of these tests is to measure population-level immunity, to get an example of how many of us in Philadelphia, for example, have been exposed to this virus,” Hensley said.

The more people exposed would theoretically mean COVID-19 is less of a threat.

People who are interested in antibody tests are advised to only use FDA-approved home tests.

Regardless of the result, doctors say it’s important for everyone to still practice safety measures.

Stephanie Stahl