Icelandic COVID-19 Study: Long-Lasting Antibodies and 0.3% Death Rate
There is new research out of Iceland that suggests the body’s immune response to COVID-19 lasts longer than other research has suggested. The study, published in the New England Journal of Medicine, described the results of tests on more than 30,000 people in Iceland. It was conducted by Reykjavik-based deCODE Genetics, a subsidiary of U.S.-based Amgen, along with several Icelandic hospitals, universities and health officials.
The research team measured antibodies in serum samples from 30,576 people in Iceland using six assays and identified the appropriate measure of seropositivity as being positive results with both pan-Ig assays. They tested 2,102 samples collected from 1,237 people up to four months after diagnosis by a qPCR assay and measured antibodies in 4,222 quarantined people who had been exposed to SARS-CoV-2 and in 23,452 people who were not known to have been exposed.
Of the 1,797 people who recovered from COVID-19, 1,107 of the 1,215 who were tested, or 91.1%, were seropositive. Of the quarantined individuals, 2.3% were seropositive. And of people with unknown exposure, 0.3% were positive.
The researchers estimate that 0.9% of the Icelandic population was infected and that the infection was fatal in 0.3%. They also estimated 56% of all SARS-CoV-2 infections in Iceland were diagnosed with qPCR, and 14% were in people who were quarantined but who had not been tested with qPCR or who had not received a positive result, if they were tested. They found 30% of people outside quarantine with COVID-19 had not been tested with qPCR.
The overall conclusion is that antibodies against the SARS-CoV-2 virus did not decline within four months after diagnosis and that the risk of death from infection was 0.3%.
This should be compared to research published in the New England Journal of Medicine in late July that suggested antibodies developed after a mild infection decay and disappear within a few months. They may still offer protection, however. That research was published by investigators at the David Geffen School of Medicine at the University of California, Las Angeles, and published as a letter. They confirmed 30 out of 34 participants using a PCR assay. They also found that the antibodies had a half-life of 73 days, which was consistent with research out of China.
The Icelandic group points out that this does not mean that all countries’ populations will be the same or that every individual has the same response. There have been at least two cases where people have been reinfected. The Icelandic study doesn’t address that issue or determine how much or which type of antibody provides immunity or protection.
Researchers from Harvard University and the U.S. National Institutes of Health (NIH) wrote a commentary published along with the Icelandic study. They note that pathogen detection, such as SARS-CoV-2 RNA testing, without antibody testing, will not be enough to track and contain the pandemic, writing, “the cost, complexity, and transient nature of RNA testing for pathogen detection render it an incomplete metric of viral spread at a population level. Instead, the accurate assessment of antibodies during a pandemic can provide important population-based data on pathogen exposure, facilitate an understanding of the role of antibodies in protective immunity, and guide vaccine development.”
They reinforce one of the findings from the Icelandic study, which was that about a third of the people who tested positive were in people with no symptoms. They also wrote, “The most striking observation was that antibodies remained stable over the four months after diagnosis, a finding captured in a subgroup of longitudinally monitored subjects. Unlike previous studies, this study suggested stability of SARS-COV-2 humoral immunity.”