I think Tyler Cowen is correct that herd immunity theories are insufficient to sustain anti-lockdown arguments.
A better foundation for anti-lockdown arguments is to be found in the social and economic consequences of lockdown policies, such things as demoralization, increased suicide rates, business failures, the dislocation of medical services (e.g., the cancellation of life-improving elective surgeries), and the disruption of schooling. These consequences, and others, are measurable, but they represent unseen costs when the lockdown debate focuses solely on mortality rates as many herd immunity theorists have done.
Still, I think Cowen is incorrect to suggest that herd immunity theories may have been flawed due to recent “second wave” observations that were not predicted. It seems to me that the cause of the “second wave” observations is not well understood at present, meaning that there’s no basis for saying anything one way or the other about herd immunity theories.
Put another way, I think the statement “few deaths, we don’t need lockdowns!” remains valid, although, as stated, fewer deaths from Covid is not the only reason lockdowns should cease.