We know that a small percentage of people who contract COVID-19 perish, which is terrible. We also know that millions of people get the disease and never know they had it.
By sampling the population, researchers can determine how many people are likely to have had the disease but never reported it because their case was either mild and felt like a cold or they had no symptoms at all.
With the virus running through the nation for about a year and vaccinations ramping up, we can now make a pretty good estimate of how many people have already been infected plus those who have been vaccinated to arrive at a total number of people no longer at risk.
The number is bigger than you might think, and the recent trend of cases falling 77% over the past six weeks shows that we’re on the right track.
Testing has been capturing only 10% to 25% of infections, depending on when during the pandemic someone got the virus. Applying a time-weighted case capture average of 1 in 6.5 to the cumulative 28 million confirmed cases would mean about 55% of Americans have natural immunity.
Think about that, more than half the nation has already had the disease.
Now add people getting vaccinated. As of this week, 15% of Americans have received the vaccine, and the figure is rising fast. Former Food and Drug Commissioner Scott Gottlieb estimates 250 million doses will have been delivered to some 150 million people by the end of March.
Put the two together and we see that 70% of the nation has already had the disease or been vaccinated. We will achieve herd immunity when we get to 80%, which is just 6 weeks or so away.
There is reason to think the country is racing toward an extremely low level of infection. As more people have been infected, most of whom have mild or no symptoms, there are fewer Americans left to be infected.
Antibody studies almost certainly underestimate natural immunity. Antibody testing doesn’t capture antigen-specific T-cells, which develop “memory” once they are activated by the virus. Survivors of the 1918 Spanish flu were found in 2008—90 years later—to have memory cells still able to produce neutralizing antibodies.
So if you’re hesitating about making summer travel plans, get over the anxiety and make those reservations. If you don’t, you’re likely to find that someone else has nabbed that hotel room or airplane seat ahead of you.