Amid Covid’s dire warnings, a crucial fact has been largely overlooked: 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 plummeting much faster than experts predicted?
Largely because the natural immunity from previous infection is much more common than can be measured by testing. The tests have captured only 10% to 25% of infections, depending on when someone caught the virus during the pandemic. Applying a time-weighted average case capture of 1 in 6.5 to the 28 million cumulative confirmed cases would mean that about 55% of Americans have natural immunity.
Now add people being 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 around 150 million people by the end of March.
There is reason to think that the country is running towards an extremely low level of infection. As more people became infected, most with mild or no symptoms, there are fewer Americans to be infected. On the current track, I hope that most of Covid left 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” as soon as they are activated by the virus. Survivors of the 1918 Spanish flu were found in 2008 – 90 years later – with memory cells still capable of producing neutralizing antibodies.