Study Finds Coronavirus Immunity Lasts Four Months after Infection, Offering Hope for COVID Vaccine Efforts

A new study has found that antiviral antibodies against SARS-CoV2 do not decline within four months of diagnosis, as some earlier reports had suggested.

Scientists at deCODE genetics (Reykjavik, Iceland), a subsidiary of Amgen Inc. (Thousand Oaks, CA, USA), conducted the study to obtain an understanding of the nature and durability of the humoral immune response to infection by SARS-CoV-2, the virus that causes COVID-19.

The scientists measured antibodies in the sera of 30,576 persons in Iceland (8.4% of the country’s population) 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 four 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. Out of the 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%. Among the 1,797 persons who recovered from SARS-CoV-2 in Iceland, 1,107 (91.1%) were seropositive.

The study was the most extensive one yet on the immune system's response to the novel coronavirus over time and offers hope for the ongoing efforts to develop COVID-19 vaccines. Previous studies have suggested that titers of antibodies against SARS-CoV2 fade quickly, raising concerns over long-term immunity provided by COVID-19 vaccines. If a COVID-19 vaccine can boost production of long-lasting antibodies against SARS-CoV2 similar to natural infection, then this offers hope that "immunity to this unpredictable and highly contagious virus may not be fleeting," scientists from Harvard University and the US National Institutes of Health wrote in a commentary published with the study in the New England Journal of Medicine.

"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," said Kari Stefansson, CEO of deCODE genetics and senior author of 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."

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