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Titers of antibodies do not decline within 4 months according to Icelandic study

Kari Stefansson

Scientists at deCODE genetics in Iceland, a subsidiary of Amgen, and their collaborators, have published a study in The New England Journal of Medicine, that shows that antiviral antibodies against SARS-CoV2 do not decline within four months of diagnosis.

The aim of the study was to obtain understanding of the nature and durability of the humoral immune response to infection by SARS-CoV-2.

“The best measure of seropositivity was a positive result with both pan-Ig assays.”

To that end the scientists measured antibodies in the sera of 30,576 persons in Iceland (8.4% of the nation) using six assays (two of them pan-Ig) and determined that the best measure of seropositivity was a positive result with both pan-Ig assays. They tested 2.102 samples from 1,237 qPCR-positive persons obtained up to 4 months from diagnosis. They also measured antibodies in 4,222 samples from exposed, quarantined persons and 19 000 persons not known to have been exposed.

Of quarantined persons, 2.3% were seropositive and of those with unknown exposure, 0.3% were positive.

The scientists estimate that 0.9% of Icelanders were infected by SARS-CoV-2 and 44% of people infected with SARS-CoV2 in Iceland were not diagnosed with qPCR. The infection fatality rate is 0.3%.  Of the 1,797 persons who recovered from SARS-CoV-2  in Iceland, 1,107 (91.1%) were seropositive.

“Furthermore it is clear that 99.1% of Icelanders are still vulnerable to SARS-CoV2. We are now focused on studying cell mediated immunity in those who do not raise antibodies.”

“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,” says Kari Stefansson, CEO of deCODE genetics and senior author on the paper. “Furthermore it is clear that 99.1% of Icelanders are still vulnerable to SARS-CoV2. We are now focused on studying cell mediated immunity in those who do not raise antibodies.”

Photo of Kari Stefansson: Christopher Lund