More than a dozen scientists recently reported to The New York Times that COVID-19 herd immunity – which is “indirect protection from infectious disease that occurs when a sufficient percentage of a population has become immune” – may have as low a threshold as 50% and have estimated that an “end” to the virus may be nearer than originally thought. Multiple studies that are still underway seem to be showing the same.
Epidemiologist Bill Hanage of the Harvard T.H. Chan School of Public Health stated, “I’m quite prepared to believe that there are pockets in New York City and London which have substantial immunity.” Professor of Theoretical Epidemiology at Oxford University Sunetra Gupta, who has warned against the risks of continued lock down, seconded the notion in an interview which received widespread backlash. In another study showing a 10-20% herd immunity threshold in Belgium, England, Portugal and Spain, it was noted:
“At least in countries we applied it to, we could never get any signal that herd immunity thresholds are higher. I think it’s good to have this horizon that it may be just a few more months of pandemic.”Gabriela Gomes, mathematician at the University of Strathclyde
Many researchers say it is unclear how long someone can maintain immunity or if it is possible to be reinfected. Jeffrey Shaman, an epidemiologist at Columbia University, warned, “I think we’d be playing with fire if we pretended we’re done with this.” Gregory A. Poland, a vaccinologist at the Mayo Clinic, said he believes we are still “Mars length” away from herd immunity.
“We are still nowhere near back to normal in our daily behavior. To think that we can just stop doing all that and go back to normal and not see a rise in cases I think is wrong, is incorrect.”Virginia Pitzer, mathematical epidemiologist at the Yale School of Public Health
It was noted by some researchers that different demographics may have differing herd immunity thresholds, and that those most vulnerable – the elderly, health compromised, and others such as the black and Latino population – may require a higher threshold than others. Some suggested that vaccinating the sub-groups who were most at-risk could “lead to the greatest benefit” regarding herd immunity.
“It’s hard to predict what’s going to happen…There are so many factors coming into play.”Cheong-Hee Chang, immunologist at the University of Michigan