During a 90-minute town hall hosted by ABC News in the must-win battleground of Pennsylvania, President Trump defended his repeated assertion that the virus will eventually disappear even without a vaccine, citing what he called “herd mentality,” an apparent reference to “herd immunity.” “And you’ll develop, you’ll develop herd — like a herd mentality. It’s going to be — it’s going to be herd developed – and that’s going to happen. That will all happen,” Trump said.

However, in the last week, leading epidemiologists from respected institutions have, through different methods, reached the same conclusion that about 85 to 90 per cent of the American population is still susceptible to SARS-CoV-2 virus. The New York Times reports of the infected percentage of the United States based on testing and death data from all 50 states. Three epidemiological modelling teams were involved in the process. The Prevention Policy Modeling Lab at Harvard’s T.H, Chan School of Public Health, the University of Minnesota’s Center for Infectious Disease Research and Policy, and the Covid-19 Projections website. The calculations appeared strikingly similar, concluding that only 10 percent to 16 percent of Americans have had the virus, leaving up to 90 percent of the population vulnerable.

The theory that the U.S. may have already achieved herd immunity and therefore, we should return to our daily lives is circulating between the Trump administration and conservative news programs and is gaining credibility on Wall Street. If this theory is accepted, however, and if individuals took off their masks and went back to hanging out in bars and piling into offices and subways, experts say that hundreds of thousands more of the U.S. population would die.

A French aircraft carrier, the Brazilian city of Manaus, the slums of Mumbai and a neighbourhood in Queens, N.Y., even in locations where the pandemic hit particularly hard until 60 percent of the population was infected, infections did not noticeably slow down. And even those levels may not be enough, given that cases are rising again in Brazil and in areas of Brooklyn that have seen cases spike and then drop off.
When looking at the history, Measles, mumps, polio, and chickenpox are examples of infectious diseases that were once very common but are now rare in the U.S. because vaccines helped to establish herd immunity. Sometimes outbreaks of vaccine-preventable diseases occur in communities with lower vaccine coverage because they do not have herd protection. The 2019 measles outbreak at Disneyland is a good example. For infections without a vaccine, even if many adults have developed immunity because of prior infection, the disease can still circulate among children and still infect those with weakened immune systems. This was seen for many of the aforementioned diseases before vaccines were developed. Other viruses like the flu virus can mutate over time, so antibodies from a previous infection provide protection for only a short period of time. For the flu, this is less than a year. If SARS-CoV-2, the virus that causes COVID-19, is like other coronaviruses that currently infect humans, we can expect that people who get infected will be immune for months to years, but probably not their entire lives.

“Immunity in 2020 is no closer to being just around the corner than prosperity was in 1930,” says Dr Thomas R. Frieden, a former director of the Centers for Disease Control and Prevention. “The route to immunity without a vaccine would be through graveyards filled with hundreds of thousands of Americans who did not have to die. When infection rates rise and fall over time; we may relax social distancing measures when numbers of infections fall, and then may need to re-implement these measures as numbers increase again. The prolonged effort will be required to prevent major outbreaks until a vaccine is developed. Even then, SARS-CoV-2 could still infect children before they can be vaccinated or adults after their immunity wane. But it is unlikely in the long term to have the explosive spread that is experienced right now because much of the population will be immune in the future. However, scientists say that wearing a mask is much more effective than hoping you and the people around you will develop herd immunity over time.

By Jumana Jabeer