By Robbie Whelan and Brianna Abbott, The Wall Street Journal

Doctors say what constitutes a sufficient level of protection against the virus isn’t known

Some people are taking Covid-19 antibody tests to determine whether they might be protected against the virus. Many health officials and doctors wish they wouldn’t.

Antibody tests are one tool some people are deploying to help them decide which precautions to take to protect themselves and curb the spread of Covid-19. Some vaccinated people say they want to know whether their protection has weakened to the point that they should get a booster, while some previously infected people say they want to measure the strength of the response the virus generated in their immune systems.

Katy Savage, 41 years old, doesn’t want to get a Covid-19 vaccine because she worries about side effects for her unborn child. She survived an August bout with the disease that put her on a ventilator for nine days and thinks immunity from that infection is enough to protect her. The Centers for Disease Control and Prevention has recommended since August that expecting mothers or women who plan to get pregnant take the vaccine, citing research showing the shots are safe and effective during pregnancy.

She plans to get a test later this month to see if she still has antibodies circulating in her blood.

“To me that would be, ‘OK, cool, I’m still good. I’m still safe,’ ” Ms. Savage said.

But it isn’t known what level of antibodies effectively prevents infection or a severe case of Covid-19, said Emily Volk, president of the College of American Pathologists. She said getting a positive antibody test isn’t a substitute for getting vaccinated.

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