Rutgers researchers find link between coronavirus symptom severity, level of specific antibody

A recent Rutgers study found that individuals who have had severe or long-lasting cases of the coronavirus disease (COVID-19) are more likely to have high levels of a certain antibody that can help prevent future infection.

While previous research has looked at ill and hospitalized populations, typically with symptomatic illness, the Rutgers study was unique in that it recruited individuals prior to them being diagnosed with infection, according to a press release.

Daniel B. Horton, co-lead author of the study and an assistant professor at Rutgers Robert Wood Johnson Medical School, said this approach allowed for a more extensive look into long-term antibody response since researchers were able to assess people across a range of COVID-19 severity, including asymptomatic patients. 

“We recruited participants before infection because we wanted to study risk factors for becoming infected and the rates at which certain groups, including health care workers, became infected,” he said.

The study observed 831 individuals, including 548 health care workers, who were previously undiagnosed with COVID-19, over a period of six months with regular testing and surveys.

One of the main methods of testing involved measuring the levels of immunoglobulin G (IgG) antibodies, which are molecules that are naturally produced by the immune system after being exposed to foreign proteins, like those made by viruses and bacteria after an infection, Horton said. 

“(IgG antibodies) represent one source of immune protection in the case of re-exposure to an infectious microbe due to the antibodies’ ability to block the microbes or activate other parts of the immune system against the microbes,” he said. “For example, the IgG antibodies measured as part of our study target a part of the SARS-CoV-2 virus (the spike protein) that helps the virus enter human cells — the same part of the virus that is targeted by the COVID-19 vaccines.”

Horton said the study found that participants who faced more severe and longer-lasting symptoms were more likely to have higher antibody levels compared to those who had mild to no symptoms or shorter illness.

Emily Barrett, co-lead author of the study and an associate professor at the Rutgers School of Public Health, said the majority of infected participants had moderate immune protection from having measurable levels of antibodies throughout the course of the study. The small remaining percentage of participants who did not have moderate immune protection were mainly asymptomatic and would likely not even have known they were infected if not for the study’s regular testing.

While it may be possible for IgG antibodies to provide protection against future infection, Horton said the amount of protection is currently unknown as there are many factors involved such as the specific type of IgG antibody and other types of immune cells.

He said neutralizing antibodies, which block the virus, tend to be more protective against repeat infections, and their effect can be amplified by T cells and B cells which work together to respond to infection in cases of repeat exposure in both unvaccinated and vaccinated individuals. 

“We also know that repeat infections or breakthrough infections after vaccination, though uncommon, tend to be milder on average than primary infections in unvaccinated individuals,” Horton said.

Barrett said the researchers found that health care workers in hospital settings, particularly nurses, were twice as likely to become infected with COVID-19, especially during the early months of the pandemic, and typically faced more severe symptoms than others.

The study also found that one-third of infected participants had symptoms that lasted at least one month, and 10 percent had symptoms that lasted at least four months, Horton said.

“That tells us that for many people, the consequences of COVID-19 go far beyond the initial infection and can have a real impact on daily life and activities over time,” Barrett said.

Additionally, she said the study participants from Newark were more likely to be infected than those from New Brunswick, which is consistent with New York City being one of the early epicenters of the pandemic in the U.S.

In the future, Barrett said researchers will continue to look at the long-term effects of COVID-19 on health and well-being among the study cohort, and will hopefully learn more about the role of IgG antibodies in protecting against infection for both vaccinated and unvaccinated individuals.

“We’ll also be studying vaccination, the delta variant and boosters — for instance, we hope to compare antibody levels in our vaccinated participants before and after a booster shot this fall,” she said.