Covid-19: Do many people have pre-existing immunity?
Even in local areas that have experienced some of the greatest rises in excess deaths during the covid-19 pandemic, serological surveys since the peak indicate that at most only around a fifth of people have antibodies to SARS-CoV-2: 23% in New York, 18% in London, 11% in Madrid.123 Among the general population the numbers are substantially lower, with many national surveys reporting in single digits.
With public health responses around the world predicated on the assumption that the virus entered the human population with no pre-existing immunity before the pandemic,4 serosurvey data are leading many to conclude that the virus has, as Mike Ryan, WHO’s head of emergencies, put it, “a long way to burn.”
Yet a stream of studies that have documented SARS-CoV-2 reactive T cells in people without exposure to the virus are raising questions about just how new the pandemic virus really is, with many implications.
Not so novel coronavirus?
At least six studies have reported T cell reactivity against SARS-CoV-2 in 20% to 50% of people with no known exposure to the virus….Read More » “Covid-19: Do many people have pre-existing immunity?”
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