About 65 million US residents (19.7%) likely had COVID-19 by Mar 7, the model shows. Until that point, only about 1 of every 2.3 infections had been confirmed, suggesting that about 60% of all infections had been unreported.
“Our results indicate that a large majority of COVID infections go unreported,” the authors wrote. “Even so, we find that the United States was still far from reaching herd immunity to the virus in early March 2021 from infections alone. This suggests that continued mitigation and an aggressive vaccination effort are necessary to surpass the herd-immunity threshold without incurring many more deaths due to the disease.”