It should be noted that R0 won't be constant - the more people have it the lower the R0 since more people will have immunity and more of the extroverts / travel

It should be noted that R0 won't be constant - the more people have it the lower the R0 since more people will have immunity and more of the extroverts / travelers (who are high R0) will have spread it around to each other already. Also, of course, the R0 always goes below 1 in summer...