“After a period of falling Covid-19 illness rates, the recent spread of the delta variant of SARS CoV-2 was a major disappointment and necessitated a reexamination of some previous assumptions.  This reconsideration may, at least in part, be a correction to overly optimistic views of what highly effective SARS-CoV-2 vaccines could accomplish. Some observers had hoped the vaccines could eliminate transmission of the virus, the ultimate goal of reaching herd immunity. 1 A more likely picture of our future with this virus comes into focus if we examine the well-known infection patterns of another respiratory virus, influenza, both in and outside pandemics. That experience can help us reset expectations and modify goals for dealing with SARS-CoV-2 as it further adapts to a global spread.

Early results from the clinical trials and observational studies of mRNA vaccines against SARS-CoV-2 indicated that not only were they are highly effective at preventing symptomatic infection, but they were also effective in preventing asymptomatic infection and therefore transmission. 2 The basic criterion used for emergency use authorization by the Food and Drug Administration was a standard one: prevention of laboratory-confirmed clinical infection meeting a case definition. The effect on asymptomatic infections was a welcome surprise because it has been thought that most vaccines for respiratory illnesses, including influenza, are “leaky” — that is, they allow some degree of asymptomatic infection and are better at preventing symptomatic infection.”

To read more from Arnold S. Monto, M.D. Please use this link below.

The Future of SARS-CoV-2