Coronavirus immunity can last up to five months – and maybe even longer – in the majority of survivors, a new study suggests.
Researchers found that those who had mild-to-moderate illness, about 90 percent of people, had a robust and stable immune response against COVID-19.
What’s more, most of these patients had antibodies that were able to neutralize, or kill, the virus, known as SARS-CoV-2.
The team, from the Icahn School of Medicine at Mount Sinai in New York City, says the findings show it is very likely decrease the odds of reinfection – and if it occurs – severely weakens the disease..
It comes on the heels of a study from the UK that found a more than 26 percent decline in COVID-19 antibodies over the course of three months.
About 70% of coronavirus survivors had high levels of antibodies, 22% had moderate levels and 8% had low levels (above)
All of the blood serum in the high groups had neutralizing activity against the virus’s spike protein as did 90% in the moderate group and 50% in the low group (above)
Patients had stable response after three months with only modest declines after five months (above)
‘While some reports have come out saying antibodies to this virus go away quickly, we have found just the opposite,’ said senior author Dr Florian Krammer, a professor of vaccinology at the Icahn School of Medicine.
‘[M]ore than 90 percent of people who were mildly or moderately ill produce an antibody response strong enough to neutralize the virus, and the response is maintained for many months.’
For the study, published in the journal Science, the team looked at data from more than 30,000 individuals screened at The Mount Sinai Health System between March 2020 and October 2020.
The antibody test used was the enzyme-linked immunosorbent assay (ELISA), which looks for antibodies that attach to the spike protein the virus uses to enter and infect human cells.
It is also capable of measuring the titer, or level, of antibodies an individual has.
Antibody test results using distinct dilutions set at 1:80, 1:160, 1:320, 1:960 or 1:2800, with each score indicating the number of times the scientist can dilute a patient’s blood and still be able to detect the presence of antibodies.
Titers of 1:80 and 1:160 were categorized as low; 1:320 as moderate; and 1:960 or 1:2880 as high.
Of the 30,000-plus patients, about 7.1 percent of patients had low levels, 22.5 percent had moderate levels and 70.4 percent had high levels.
This means more than 90 percent of coronavirus survivors had moderate-to-high levels of anti-spike antibodies.
Additionally, about 50 percent of blood serum in the low range had neutralizing activity as did 90 percent in the moderate range and all did in the high range.
Next, the team recalled 121 plasma donors who had a variety of levels to repeat antibody test three months after recovering and again at five months.
Results showed slight drops after each tests, but a moderate level was retained by most people five months later
In an interesting findings, there was an increase in levels among those who originally tested as have low or moderate antibody levels.
It may explain the findings of the British study, with 6.6 precent of those having antibody responses to the virus in June and 4.4 percent in September – because those with mild cases have responses that take a longer time to mount.
‘The serum antibody titer 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 first author Dr Ania Wajnberg, Director of Clinical Antibody Testing at The Mount Sinai Hospital.
‘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. We will continue to follow this group over time to see if these levels remain stable as we suspect and hope they will.’