A vast majority of individuals infected with mild-to-moderate COVID 19 mount a “robust” defence via antibodies that is relatively stable for “at least five months”, according to a new study which says this immune response significantly reduces the risk of re-infection with the novel coronavirus.
The research , published in the journal Science , found that this antibody response correlates with the body’s ability to neutralise the SARS-CoV-2 virus that causes COVID-19.
“While some reports have come out saying antibodies to this virus go away quickly, we have found just the opposite — that more than 90% of people who were mildly or moderately ill produce an antibody response strong enough to neutralise the virus, and the response is maintained for many months,” said Florian Krammer, a senior author of the study from The Mount Sinai Hospital in the U.S.
“Uncovering the robustness of the antibody response to SARS-CoV-2, including its longevity and neutralising effects, is critically important to enabling us to effectively monitor seroprevalence in communities and to determining the duration and levels of antibody that protect us from reinfection,” Krammer said.
To screen individuals, the scientists used an antibody test called an enzyme-linked immunosorbent assay (ELISA) to detect the virus’ telltale spike protein which enables it to attach and gain entry into our cells.
Based on the findings, the scientists said a vast majority of positive individuals had moderate-to-high levels of antibodies that can neutralise the coronavirus spike protein.
The scientists then recalled 121 recovered COVID-19 patients for repeat antibody testing at approximately three and five months post-symptom onset. They saw a slight drop in the antibody levels in these individuals from the first to second testing time point, and another drop for the last testing time point.
According to the researchers, this indicated that a moderate level of antibody is retained by most people five months after symptom-onset.
“The serum antibody titre we measured in individuals initially were likely produced by plasmablasts — cells that act as first responders to an invading virus and come together to produce initial bouts of antibodies whose strength soon wanes,” said Ania Wajnberg, another co-author of the study. “The sustained antibody levels that we subsequently observed are likely produced by long-lived plasma cells in the bone marrow. This is similar to what we see in other viruses and likely means they are here to stay.”
According to the scientists, the vast majority of individuals with antibody titres of 320 or higher showed neutralising activity in their serum that are stable over a period of at least three months with only modest declines at the five-month time point. Although this cannot provide conclusive evidence that these antibody responses protect from re-infection, the researchers believe the antibodies could decrease the odds of getting reinfected, and may attenuate disease in the case of breakthrough infection.