I have read Erin's article several times. The quantitative data with respect to amount of virus exposure from the various examples is compelling and deserves a serious follow-up with solid scientific testing. It seems that minimal virus presence allows the exposed person to escape getting ill, certainly seriously ill! The more the presence or concentration of virus the greater the chance of contacting Covid-19 e.g. as in dense population situations like old age homes, enclosed spaces like ocean liners, etc. In parallel to those catching Covid-19 there seems to be a much larger population that is asymptomatic but tests positive as carriers. So I pose this question - can it be that minimal exposure to the virus allows a body time to develop antibodies more or less in parallel to the virus replicating itself? In this way the virus can never overpower a body's defense mechanisms. Over a few weeks the body creates sufficient antibodies to win the fight but during this time of internal battle, there are positive Covid-19 tests. The assumption is that humans can develop antibodies quickly and efficiently when not submersed in heavy doses of in-coming Covid-19 but are overwhelmed in their capability to counter heavy initial virus concentrations. In the latter case, the virus wins by simple brute force, gains access to the lungs and other organs and so promotes total body failure before antibodies can catch up. In summary, can small controlled exposures (injections, nasal spray) to live Covid-19 virus temporarily, at least, equate to having the now missing vaccine in turning the more fatal aspects of the disease? Covid- 19 displays different characteristics to its predecessors so may we assume that our bodies can adapt and develop antibodies at sufficient rates in most exposure situations? Thoughts? (P.S. I am a lay person and not in health care but a chemical engineer who knows reaction rate characteristics and has a logical thought process).