The long term end of the COVID-19 pandemic is that most of the world acquires herd immunity. We can do it through either large fractions of the population getting infected and a significant fraction of the infected population recovering or through vaccination or through a bit of both. The differences in approaches will be measured by time and body bags.
One of the optimistic scenarios for COVID-19 is an asymptomatic hypothesis. This hypothesis contends that there is a large pool of individuals who are immune to COVID-19 because they had a very mild or asymptomatic infection over the winter. These people would now be immune to COVID and can be released from physical distancing and resume critical medical and economic activity. The more optimistic variants of this optimistic scenario would have continual and widespread asymptomatic infection continue even as we have physically distanced over the past three weeks. If this family of scenarios is close to reality, we would have widespread herd immunity fairly quickly without needing to wait for a vaccine.
The test for these scenarios would be widespread serological testing. Serological testing looks for antibodies in the blood of an individual. Antibodies are what recognize and attack a pathogen and they thus serve as a good history book of diseases that an individual’s immune system has mobilized against in the past. If someone was aysmptomatic while infected, a serological test would reveal that they had actually been infected.
Serology testing is not widespread nor common at this time. However, one of the Colorado ski resort counties, San Miguel County where Telluride is located, has done serological testing on about 1,000 residents. There is no huge reservoir of individuals who have recovered from asymptomatic infections:
COVID-19 in San Miguel County, only eight, or about one percent have come back positive. Another 23 have either indeterminate or borderline results, which means the person may have been exposed to the virus, but their immune system hasn’t yet produced enough antibodies to register a positive on the test…
San Miguel County was the first place to embark on testing for all. Anyone could get a COVID-19 blood serum test, healthy or not. So far, they have tested about 12 percent of the county’s 8,000 residents.
This is very valuable information. It is telling us that there is unlikely to be a large, natural and pain free herd immunity that has been developed over the past few months. It precludes a pathway which means resources and attention can be more effectively and efficiently focused on other pathways that hold more promise.