Second of all, herd immunity depends on the biology of the virus and the vast complexities and variations of our immune responses. Earlier, in her dismissal of anticipating vaccines, Yih asserts, “neither the effectiveness nor the duration of immunity from any of these vaccines is known as yet.” But the same is true of natural herd immunity. We simply don’t know the duration, exact mechanisms, or efficacy of the human response to this coronavirus. There have been a growing number of apparent reinfections. We don’t know how long immunity lasts. If it is of short duration, that would seem to preclude herd immunity or mean that an impossibly high proportion of the overall population must be infected at any one time for it to occur.
We don’t know why, in some cases, antibodies are not produced. We don’t know why some of those exposed don’t contract the virus. We don’t know why apparent asymptomatics later develop long-term pathologies. Most basically, we don’t know what proportion of the population must be infected to attain herd immunity. In other words, the same caveats apply to herd immunity as to vaccines, but with much more statistical uncertainty, since allowing viral transmission in the population at-large is not a phased, controlled experiment. Researchers can turn on and off vaccine trials, as recently happened with the AstraZeneca trials, but they can’t put the genie back in the bottle (except through the same containment measures Yih/Kulldorff condemn) once community transmission starts.
Kulldorff further explains,
children and young adults have minimal risk, and there is no scientific or public health rationale to close day care centers, schools, or colleges. In-person education is critically important for both the intellectual and social development for all kids, but school closures are especially harmful for working-class children whose parents cannot afford tutors, pod schools, or private schools.
Bewilderingly, his first argument abstracts from the very population health arguments he and Yih seek to rely on. The rationale for closing “day care centers, schools and colleges” is not simply the risk to young people, who may have “minimal risk” for severe symptoms, but not for infection and transmission. In fact, transmission rates among young people are the highest of any age-based demographic. The major risk, here, is to teachers, school staff and all the adults in those children’s lives. Moreover, health professionals and researchers are also now finding a host of serious chronic pathologies appearing long after recovery among children and in asymptomatic cases.
Kulldorff’s second argument regarding working-class families simply reprises the obvious and constant barrage of Hobbesian choices imposed on all working-class people in our society, dilemmas which will only be resolved through socialist revolution. Working-class families must inevitably struggle for reforms that could mitigate those choices. But it would make more sense – given Covid-19 epidemiology and the potential cost in lives – to demand paid time off for parents to supervise home-bound, distance-learning children, than it would to take some unspecified measures to prevent transmission among children in confined classrooms, and from them to adults.
Kulldorff rightly points out that both vaccines and exposure can result in herd immunity. He states,
whatever strategy we use for COVID-19, we will eventually reach herd immunity, either with a vaccine, through natural infections, or a combination of the two. So, the question is not whether we get to herd immunity or not.