Friday, October 30, 2020
Immunity. The concept seems intuitive. But whose immunity? How long? How strong? What kind? I’ve spent half the morning trying to reconcile these two recent reports from CNN: “Immunity to coronavirus lingers for months, study finds” and “British study shows evidence of waning immunity to Covid-19.” What do they tell us about immunity and what conclusions can we draw from them? (See article links below).
Basically, one study analyzes the persistence of immunity in individuals and the other looks at the persistence of immunity in a population. Just to make sure I understood correctly, I went back to the source papers. Here’s my take on what they tell us:
“Immunity to coronavirus lingers for months:” The CNN news article states: “90 % of people who recover from Covid-19 infections keep a stable overall antibody response.” This report is based on a research article in Science titled: “Robust neutralizing antibodies to SARS-CoV-2 infection persist for months,” Science reports two studies from the Icahn School of Medicine at Mount Sinai Health System in New York City.
The first study asked whether people who had contracted mild to moderate Covid between March and October had developed a strong antibody response. They tested 30,082 samples from people known to be positive for antibodies, taken from convalescent plasma donors and from employee volunteers. [Note–both healthy adult populations]. Over 90% were found to have antibodies to the spike protein and by serial dilution testing these antibodies were found to be moderate to high titer, in other words, “robust.”
The second study followed a much smaller group of individuals over time. They tested 121 plasma donors 3 months and 5 months after infection and found that the titers were “relatively stable.”
In both studies, the antibodies were tested for neutralizing activity against actual SARS-Cov-2 in the lab. So the study indicates that people infected with mild to moderate Covid-19 form neutralizing antibodies which can last up to 6 months. The researchers plan to follow up with the plasma donor cohort. Follow-up questions: Do these antibodies protect people from reinfection? For how long?
“British study shows evidence of waning immunity to Covid-19.” The CNN news article states: Home finger-prick tests sent to “more than 365,000 people in England found a more than 26% decline in Covid-19 antibodies over just three months.” This article is based on a pre-print report titled: “Declining prevalence of antibody positivity to SARS-CoV-2: a community study of 365,000 adults.”
This study did not look at the same 365,000 individuals over time. Instead it surveyed three random groups of people who responded to invitations from the National Health Service. Results from 99,908 people tested 12 weeks after the April peak in infections were compared to results from 105,829 different people tested 18 weeks after, and to 159,367 different people tested at 24 weeks.
Unlike the first study (the Mount Sinai study above), these were not selected for people who had tested positive. This was an epidemiological study which showed that the prevalence of antibodies in the population decreased over time. It was not designed to test how long the antibodies lasted in individuals who had actually had Covid-19.
It also does not answer the questions raised by the first study: Do these antibodies protect people from reinfection? For how long? Let me add a third article to the mix: “Why You Shouldn’t Worry About Studies Showing Waning Coronavirus Antibodies,” The New York Times, Oct. 27, 2020. This article points out some of the variables that effect studies on immunity: Focusing on one kind of antibody doesn’t do justice to all the resources available in the human immune system such as cellular immunity and a spectrum of antibody responses which may fall below detectable levels but still respond to an attack. These answers are important to understand both immunity after exposure and the immune response to vaccines.
Yes, there’s hope: Many more studies are underway to help shed light on immunity, how it develops and how long it lasts. We need coordination of all this information. So I was encouraged to see the announcement in the NIH director’s blog for Oct. 20, 2020, that the National Cancer Institute has established just such a coordinated effort, the NCI Serological Sciences Network for COVID19 (SeroNet), funded by an emergency Congressional appropriation for this purpose. Now I didn’t see that in the news.
But I’ll be looking forward to seeing the results.
Today’s Source Articles:
“Immunity to coronavirus lingers for months, study finds,” CNN, Oct. 29, 2020. https://www.cnn.com/2020/10/29/health/covid-immunity-lingers-months-wellness/index.html
“Robust neutralizing antibodies to SARS-CoV-2 infection persist for months,” Science, Oct. 28, 2020. https://science.sciencemag.org/content/early/2020/10/27/science.abd7728
“British study shows evidence of waning immunity to Covid-19,” CNN, Oct. 26, 2020. https://www.cnn.com/2020/10/26/health/covid-19-immunity-wanes-large-study-finds/index.html
“Coronavirus antibody prevalence falling in England, REACT study shows,” Imperial College London, Oct. 27, 2020. https://www.imperial.ac.uk/news/207333/coronavirus-antibody-prevalence-falling-england-react/
“Declining prevalence of antibody positivity to SARS-CoV-2: a community study of 365,000 adults” Source article for above CNN article] https://www.imperial.ac.uk/media/imperial-college/institute-of-global-health-innovation/MEDRXIV-2020-219725v1-Elliott.pdf
“Why You Shouldn’t Worry About Studies Showing Waning Coronavirus Antibodies,” The New York Times, Oct. 27, 2020. https://www.nytimes.com/2020/10/27/health/coronavirus-antibodies-studies.html
“Two Studies Show COVID-19 Antibodies Persist for Months,” Dr. Francis Collins, Director’s Blog, NIH. https://directorsblog.nih.gov/2020/10/20/two-studies-show-covid-19-antibodies-persist-for-months/
Why am I doing this?
The coronavirus pandemic will be indelibly written on our memories just as the Great Depression or the Battle of Britain left their mark on past generations. It is my intention to journal the pandemic experience from three perspectives: as a retired medical technologist, a historian (Ph.D., 2014), and an ordinary person living through an extraordinary crisis.
You are on History’s Edge.