Millions of blood tests for COVID-19 antibodies will tell us how widespread COVID-19 really is. It will tell us what the worse case could actually be. Oxford had modeling which suggests that there could be very large numbers of infected and now immune people. The hope is that there is a high percentage of people who were infected and are now immune. The more people who had it then the better shape we are as a society.
The antibody home tests are part of a program of increased testing. The number of nasal swab tests, which are currently being used in hospitals to find out whether very sick patients have Covid-19, will be increased within the next couple of days. The UK as a near-term target of 25,000 tests per day. The UK has been testing 5000-8000 each day. The swab tests only indicate if someone has coronavirus right now. It does not indicate if someone already had coronavirus.
The specifications on some 15-minute tests tend to be only 98% accurate for mid-late stage and some only have 70-80% accuracy at the early stage of the disease.
We need to understand the exact numbers of false positives and false negatives from these early blood tests.
Being able to identify those with immunity would also provide more sources of people who could donate blood to provide antibody treatments to those who are sick.
The one situation where an entire, closed population was tested was the Diamond Princess cruise ship and its quarantine passengers. The case fatality rate was 1.0%, but this was a largely elderly population. Their death rate from Covid-19 is much higher.
Projecting the Diamond Princess mortality rate onto the age structure of the U.S. population, the death rate among people infected with Covid-19 would be 0.125%. There were not enough people for good statistics. The real death rate could stretch from five times lower (0.025%) to five times higher (0.625%). It is also possible that some of the passengers who were infected might die later.
Having a 0.1 to 0.2% would put the fatality rate near the 0.1% of seasonal flu. COVID-19 still can get four times worse because ICUs getting overrun.