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.

George Ofori-Amanfo, MD, Chief of the Division of Pediatric Critical Care at The Mount Sinai Hospital and Mount Sinai Kravis Children’s Hospital

Nine pediatric patients admitted to The Mount Sinai Hospital during the past two weeks, who either tested positive for COVID-19 or had antibodies, had severe abdominal pain and low blood pressure, which progressed to shock. Some of the patients also had clinical signs of myocarditis. This inflammation affects the heart muscle and the heart’s electrical system, reducing the heart’s ability to pump and causing abnormal rhythms, or arrhythmias. SARS-CoV-2, which causes COVID-19, is the first coronavirus associated with myocarditis.

Prior to their infections, the patients—six boys and three girls—did not have co-morbidities that would have put them at higher risk for disease, according to George Ofori-Amanfo, MD, Chief of the Division of Pediatric Critical Care at The Mount Sinai Hospital and Mount Sinai Kravis Children’s Hospital.

“These patients presented with very unusual symptoms,” says Dr. Ofori-Amanfo. “Until now, the pediatric patients who came to the Emergency Department with COVID-19 all had respiratory problems like the adults—dry coughs, difficulty breathing, and sometimes decreased oxygen saturation. In this recent series of patients, the children presented with abdominal pain, low-grade fever, vomiting, and in some cases diarrhea.” The pain was so severe that one child was sent to Mount Sinai to determine whether the problem was appendicitis, which was not the case. Another child was sent to the hospital for a CT scan to see whether the cause was inflamed abdominal lymph nodes. This was also ruled out upon closer examination.

Two of the nine pediatric patients also had a rash and conjunctivitis, which put their symptoms in a constellation of conditions that are similar to but not the same as Kawasaki disease, which causes blood vessels to become inflamed and also affects the heart. Both of these patients were among those with the least severe symptoms.

Dr. Ofori-Amanfo says that when the children and young adults progressed into a state of shock with low blood pressure, they did not respond to the traditional methods of resuscitation and large amounts of IV fluids, so the clinicians gave them high doses of blood pressure medication, which helped. Three of the patients required mechanical ventilation for shock and two of these patients also required mechanical cardiac support.

“This is a new phenomenon and it is rare. Perhaps these patients had mild symptoms of COVID-19 or were asymptomatic. We think what we’re seeing is a post-infectious process. It is an aggressive immune response to either the virus or some aspect of the viral infection that we don’t know yet. Because when you look at their lab profiles, the patients have very elevated inflammatory markers and this suggests an acute inflammatory response,” says Dr. Ofori-Amanfo. “The exaggerated immune response affects the heart function, which is mildly to moderately depressed, and their low blood pressure is a result of the hyper state of their immune system.”

At Mount Sinai, a team of specialists in areas that include pediatrics, immunology, hematology, infectious diseases, and basic science is treating this syndrome by targeting and modulating the overwhelming immune response and managing anticoagulation therapies for potential strokes. “This is a real entity, but it is rare, and we are hypervigilant and looking out for our patients,” says Dr. Ofori-Amanfo. “We think we have developed some therapies that are working. We have really smart, dedicated specialists working together. It is a great partnership.”

Other hospitals in the New York metropolitan region, around the country, and in Europe have reported smaller clusters of similar pediatric cases.

“We are studying the children to learn what predisposes them to developing this syndrome,” Dr. Ofori-Amanfo says. “These children had siblings. We don’t know why one child gets this but his brother or sister doesn’t.”