Researchers don’t know yet.
With some viruses, people have lifetime immunity after recovering, while immunity wanes with others, said Dr. Dawn Wooley, virologist with Wright State University.
Wooley said researchers are still trying to learn how long immunity lasts for the new coronavirus. Since it is only known to be circulating among humans since late last year, there haven’t been people in recovery long enough to have better data. Immune response can also vary by individual people, which can mean different people who have recovered might have different levels of antibodies in their systems, but research on this aspect is also limited so far with the new coronavirus.
“So what it (a positive test) does tell me is that you were exposed, and you cleared it and you produced what we consider the appropriate immune response,” Dr. Joseph Allen said Premier Health Regional Medical Director. “Are you immune forever? We don’t know. Can you get it again? It appears that it should not happen but there have been some isolated reports of folks that were reinfected.”
Allen said people who get a positive result still need to practice social distancing as recommended by public health guidelines.
Where do I get a test?
Premier Health’s drive-thru testing site now has $65 antibody testing for adults by appointment who are interested in donating convalescent plasma to help patients fighting COVID-19, or who are curious whether an unexplained respiratory illness they had earlier this year actually was the coronavirus.
“If you test positive for this disease, it means you can donate the plasma, as well. And you could potentially save three or four lives,” Allen said.
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To schedule a collection site appointment for the antibody test, go to compunetlab.com and click on Coronavirus/COVID-19. Under the Patients section is an order form and a link to schedule an appointment. In addition to scheduling an appointment, print an order form, fill it out, and bring it to the collection site along with credit card and photo ID. Test results are shared online within a couple days or by mail within 10 days.
What is an antibody test? Why do some people say serological tests or sero-surveys?
Serology is the study of blood serum. People who say antibody tests are talking about the same thing as people who say serological tests. Sero-surveys are studies of a population to look for evidence of prior infections.
Are all tests the same?
With the market flooded with antibody tests with mixed levels of accuracy, the FDA announced on Monday that coronavirus antibody testing companies must prove accuracy in 10 days in order to keep selling in the U.S.
Allen, with Premier Health, said their antibody test used with the drive-thru collection site is highly accurate, with about 99.5% sensitive and 100% specific. Tests that aren’t very specific will get false positives and tests that aren’t very sensitive will get false negatives. Both problems can spoil the accuracy of data.
What can sero-surveys tell us?
Quite a lot actually, but it depends on the quality of the testing devices (see previous question) as well as the survey design, according to Wooley.
Policy makers and public health officials have continued to struggle over data gaps when trying to craft the right COVID-19 response. Since testing for active infections is limited, researchers are still asking: how far has it spread? Are there common traits among people who get so mildly infected that they don’t know it? Or on the other hand, common traits that refine our understanding of who is most vulnerable?
Wooley said better data on how fatal the virus actually is would help dictate appropriate public health measures. She said there’s a range in fatality rates by geography, which could indicate things like different strains, differences in population health and health care, and or differences in data collection. Better surveys would help clarify this.
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“If it’s a highly transmissible virus and a high death rate, then that would push us towards an extreme measure,” Wooley said.
This news organization previously reported Ohio expanded to start tracking “probable” cases, which includes people with positive antibody tests. Previously, health officials weren’t able to count those under the outbreak total tally because the definition only included positive tests for active infections. Now, the state can report those with positive blood tests to the total tally to have a better picture of the outbreak curve.
If the quality of the survey matters, what’s does quality look like?
If you’re trying to understand how prevalent the virus is, it’s important ot have a random sample, according to Wooley.
You can’t get the U.S. average height by surveying an NBA team, and you can’t get the prevalence of spread if you test a group of people that mostly draws out people who think they were recently sick with COVID-19.
Wooley said the only way to understand is to draw survey participants “essentially off the street.”
“If you really wanted to know the true prevalence of this, we would randomly take 10,000 people and test them regardless of any symptoms,” Wooley said.
In on example, Miami-Dade County in Florida worked with the phone company to generate a random list of phone numbers and used that to invite volunteers for a study, and the county reported its results indicated 6% of the population there had been infected.
These studies could tell us if we’re getting near “herd immunity” but researchers don’t expect that to be the finding. Wooley said in general about 70% of people need to be infected to achieve herd immunity. The virus spread to near collapse of the health system in New York City, and sero-surveys indicate 20% infection rates.
Who is all doing these studies?
Ohio Department of Health is working on starting a study soon, according to a spokeswoman. CDC is working on surveys. Some Ohio hospitals and academics have started research.
What’s the big takeaway?
In short, we’re still learning what a positive antibody test really means for whether a person is immune and how long. These tests could also help more COVID-19 survivors become plasma donors to help people who are still sick.
There’s a lot of important data that could be collected by studies of blood samples designed to answer our unanswered questions, which could help appropriately tailor our response to this virus that we’re still learning so much about (but also potential for misleading data if studies are poorly designed.)