This might be done by using an approach that has worked against other viruses for years: simply feeding another virus to stimulate the body’s innate immune system, ideally the Sabin Oral Polio Vaccine (O.P.V.), which is extremely safe, available, inexpensive and a powerful stimulant of an immediate, emergency response against a wide range of other viruses beyond polio.

O.P.V. may not offer permanent immunity to Covid-19, but preliminary research from many investigators suggests that it will be effective for long enough to minimize the risk of people being infected for months when they return to work, and immunity could be sustained by periodic booster doses until a more permanent vaccine is developed and available.