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Antibodies Against COVID Do Not Decline Within 4 Months Of Diagnosis: Study

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A new study has found that antibodies against SARS-CoV-2, the virus that causes COVID-19, do not decline within four months of diagnosis.

The study was conducted by scientists at Iceland-based deCODE Genetics, a unit of American biopharma company Amgen Inc. It was published in the New England Journal of Medicine.

The aim of the study was to gain insight into the nature and durability of the humoral immune response to infection by the coronavirus.

Decode said that the scientists measured antibodies in the serum samples from 30,576 persons in Iceland, representing 8.4 percent of the nation's population, using six assays. This includes two pan-immunoglobin or pan-Ig assays.

The scientists determined that the best measure of seropositivity was a positive result for the coronavirus with both pan-Ig assays.

The scientists tested 2,102 samples collected from 1,237 persons up to four months after diagnosis by a quantitative polymerase-chain-reaction or qPCR assay. They also measured antibodies in 4,222 samples from coronavirus exposed, quarantined persons, and 19,000 persons with no known exposure to the coronavirus.

Of the 1,797 persons who recovered from the coronavirus infection, 1,107 persons, or 91.1 percent, were seropositive. Antiviral antibody titers assayed by two pan-Ig assays increased during the two months after diagnosis by qPCR and remained on a plateau, or showed no further decline, for the remainder of the study.

"We are pleased to be able to put to rest the concern that the titer of the antiviral antibodies may decline within weeks of infection. Furthermore it is clear that 99,1% of Icelanders are still vulnerable to SARS-CoV2," said Kari Stefansson, CEO of deCODE Genetics and senior author on the paper.

2.3 percent of the quarantined persons and 0.3 percent of the persons with no known exposure to the coronavirus were seropositive.

The scientists estimate that 0.9 percent of Icelanders were infected by the coronavirus and 44 percent of the people infected in Iceland were not diagnosed with qPCR. The risk of death from the infection was 0.3 percent.

The study notes that well-validated serologic assays for SARS-CoV-2 are urgently needed. A highly specific assay is required for screening populations with a low seroprevalence, such as that in Iceland.

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