Ania Wajnberg, MD, left, with Nurse Manager, Patricia Lazio, RN.
More than 99 percent of individuals who fully recovered from COVID-19 and had mild to moderate symptoms that did not require hospitalization went on to develop antibodies, according to a new study by researchers at the Mount Sinai Health System. The team looked at 1,343 people who either had confirmed cases of the disease or were suspected to have the disease between March 26 and April 10, 2020.
The study also showed that these IgG antibodies, or Immunoglobulin G—which appear after an acute infection and have the potential to confer immunity and protection against reinfection—were optimal for use in testing three to four weeks after the onset of COVID-19 and two weeks after the disease resolved.
“While we don’t know for certain whether having antibodies confers immunity at this point, or how long immunity would last, we are very encouraged that even those people who had mild cases of the disease did produce antibodies,” says the study’s first author, Ania Wajnberg, MD, Associate Professor of Medicine (General Internal Medicine) at the Icahn School of Medicine at Mount Sinai.
The encouraging findings support the potential of antibody-based blood tests to help understand the spread of COVID-19, the disease produced by the SARS-CoV-2 virus. The testing would provide lawmakers with a better understanding of how many people may possibly be immune and might be able to safely return to work as economies begin to reopen. At this time, there remains limited data worldwide on the development of antibodies to SARS-CoV-2, particularly the formation of IgG.
Mount Sinai has tested more than 22,000 individuals for antibodies since late March, when it became one of the first institutions in the world to begin treating COVID-19 patients with antibody-rich plasma from individuals who recovered from the disease. Mount Sinai identified individuals who had high titers, a measure of the concentration of antibodies, and referred them to the New York Blood Center, where they donated their plasma. As of May 11, more than 350 patients had received this convalescent plasma therapy through Mount Sinai, which is currently compiling data on the program.
The study also found that 19 percent of those who had recovered from COVID-19 still had evidence of the virus after receiving a nasopharyngeal swab of the back of their nose and throat. This has raised some concerns among patients who thought they may have been reinfected.
“More evidence is showing that people probably don’t need to be stressed about these positive swabs,” says Dr. Wajnberg. “We don’t know for certain why almost 20 percent of people had evidence of the virus weeks out from their symptoms. It is possible there’s some shedding of the virus still going on, but it is also possible that the test is picking up dead viral fragments. The scientific community is looking into this because it has major implications as to whether you need a negative swab to be cleared from this disease, which more people are thinking you don’t.”
One of the study’s authors, Florian Krammer, PhD, Professor of Microbiology at the Icahn School of Medicine at Mount Sinai, developed the antibody test that Mount Sinai uses. He says, “If you have higher titers you start to see neutralization. I can’t tell you that having a certain level of titers is protective against the virus, but we know from the vast majority of viral infections that neutralizing antibodies do protect you from getting infected. There are four human coronaviruses that give you a common cold, and in studies of those you get antibodies for one to three years and are protected during that time. In some cases you’re protected from getting reinfected, in other cases you might get a little infected but not have symptoms, and in other cases you may have symptoms but they’re much milder.”
In related news, the Mount Sinai Health System and California-based Sorrento Therapeutics, Inc. recently agreed to jointly develop antibody products that would act as a “protective shield” against SARS-CoV-2 coronavirus infection, potentially blocking and neutralizing the activity of the virus in at-risk populations, as well as recently exposed individuals.