America's Herd Immunity Fixation Should End, Scientists Say : Shots ...

People line up for COVID-19 vaccinations last month in Hagerstown, Md. Each person vaccinated helps end the pandemic, epidemiologists say, and helps lower the rate of hospitalization and death from COVID-19.The end of this pandemic sometimes gets boiled down to two words: herd immunity. It feels concrete — something to grab onto in a time filled with so much uncertainty, a finish line for which to strive.But the problem with framing the goal that way, say the scientists who actually build the models, is that the herd immunity threshold is far harder to calculate reliably than many in the public realize.Computer models aren't exactly like real lifeIn any model of the pandemic, "we make a bunch of assumptions that we know aren't true," says Samuel Scarpino, director of the Emergent Epidemics Lab at Northeastern University. Based on current conditions, and the fact that young children are not yet eligible for vaccination, Lipsitch says he believes as much as 90% to 100% of adults would need to get vaccinated to cross the threshold."Based on the best calculations I know how to do, it will be impossible or very difficult to reach [herd immunity] in many parts of the United States," he says.But that could all change again in the future, depending on new real-world conditions.And in the end, Mordecai says, it may not matter so much, in terms of corralling the virus enough so that the number of severe cases of COVID-19 significantly drops."Our vaccine campaigns rarely reach the level that we actually have herd immunity to the flu," Mordecai points out. Even though the coronavirus is a far more serious disease, "that's the kind of thing that could happen with COVID-19."In fact, none of the scientists interviewed says they believe the herd immunity threshold is the right goal for the public to worry about — they urge emphasizing vaccination instead.