doclinkin wrote:One thing that is intriguing is the hints that former coronavirus infections may confer even partial immunity or lessen the symptoms in COVID-19 infection. That seems like a promising area to study since we have had more time pass between the last few coronavirus events.
It would also help to explain why kids are virtually immune, or at least mostly asymptomatic. Kids come in contact with a lot more coronaviruses and probably have all kinds of useful T-cells circulating throughout their body.
It's also possible that a significant percentage of us are already effectively immune thanks to exposure to the right common cold coronaviruses, which may mean that the we are closer to the herd immunity threshold. Herd immunity may be effectively at 30 or 40%, not 60-70%, because 20-40% of us were immune to this thing before it even started.
Keep an eye on New York. 15-20% of their population has had it, but their daily new case rate is down to a very low 900 a day (or about 4 new cases per 100,000 people). That's down from a peak of 10,000 new cases a day - a 91% reduction. California, a state with similar lockdown restrictions but with less than 5% of population having had the virus, has seen a steady rise in case rate and are now at a 3500 new cases a day (or about 9 cases per 100,000 people). The main difference between the two states is the percentage of population who has already had it. It looks like a population immunity level as low as 20% is making a massive difference in the new case rate.