We will have herd immunity in April

Amid dire warnings from Covid, a crucial fact has been largely ignored: Cases have dropped 77% in the past six weeks. If a drug reduced cases by 77%, we would call it a miracle pill. Why is the number of cases falling so much faster than experts predicted?

In large part because natural immunity to a previous infection is much more common than can be measured by testing. Tests have caught only 10% to 25% of infections, depending on when during the pandemic someone contracted the virus. Applying a time-weighted average case catch of 1 in 6.5 to the 28 million cumulative confirmed cases would mean that roughly 55% of Americans have natural immunity.

Now add the people who get vaccinated. As of this week, 15% of Americans have received the vaccine and the number is increasing rapidly. Former Food and Drug Commissioner Scott Gottlieb estimates that 250 million doses will have been delivered to about 150 million people by the end of March.

There are reasons to believe that the country is moving towards an extremely low level of infection. As more people, most of whom have little or no symptoms, have become infected, fewer Americans remain to be infected. On the current trajectory, I expect Covid to mostly disappear in April, allowing Americans to resume normal life.

Antibody studies almost certainly underestimate natural immunity. The antibody test does not capture antigen-specific T cells, which develop “memory” once they are activated by the virus. In 2008, 90 years later, survivors of the 1918 Spanish flu were found to have memory cells capable of producing neutralizing antibodies.


Source link