Will Mass. achieve herd immunity against the coronavirus pandemic? Maybe, experts say, but it could be difficult
Original article from The Boston Globe , 2021
Massachusetts’ coronavirus vaccination campaign has been among the most successful in the country, with 57.3 percent of residents — 3.9 million people — having received at least a first shot of the vaccines as of earlier this week, according to federal data.
That progress has people wondering if the state can vaccinate enough people to reach herd immunity. Here’s what some experts think about that prospect.
What is herd immunity?
Herd immunity occurs when a large proportion of a population is immune to a virus because of previous infection or vaccination. As a result, the virus can’t readily spread, because its chances of encountering a susceptible person are low.
What percentage of a population would have to be immune to achieve herd immunity?
“There’s no magic number,” said Dr. David Dowdy, an associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health. And the number, he added in an e-mail, “depends partially on how many people have been infected, the degree of distancing that people are practicing, and the transmissibility of the virus” — a factor that can change with the season and the variant of the virus in circulation.
Still, many experts have recently settled on 80 percent as the likely target.
“We won’t know what the exact number is until we reach it and see what happens epidemiologically with cases, hospitalizations, and deaths,” said Dr. Nahid Bhadelia, an associate professor at the Boston University School of Medicine who specializes in infectious diseases.
Could Massachusetts achieve herd immunity by itself?
“We have a better shot than most other places in the world right now,” Bhadelia said in an e-mail.
But Dr. David Hamer, a physician at Boston Medical Center and a Boston University epidemiologist, said, “It’s going to be a challenge.” The federal government has not yet authorized the vaccines for people under 16, some people remain reluctant to get the vaccines, and some people have medical or religious reasons for declining.