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Vaccinations and Herd Immunity: What Will it Take?

April 14, 2021

Dr. Ulysses Wu envisions a day when the United States achieves herd immunity against the lethal COVID-19 virus still afflicting thousands nationwide.

“I would love for this to happen,” said the director of infectious diseases and epidemiology for Hartford HealthCare, adding that, “We need to get more vaccine buy-in.”

Herd immunity is created when a high enough percentage of a population is immune to a virus like COVID-19 through vaccination or actual infection with the virus, and, therefore, cannot transmit it from person to person. To achieve that, Dr. Wu said, the country needs to vaccinate more people. While herd immunity could start to occur when approximately 60 percent of people are vaccinated, he would like to push that number higher.

“We’re not even close to the more than 90 percent I would like us to get for herd immunity,” he said.

Each completed vaccine grants the person a level of protection against COVID-19 and its variants. Research has shown the level of immunity to be high, especially against severe forms of infection. The question that remains, however, is how long such immunity lasts in humans.

“We don’t know how long we’re immune after getting the vaccine because this is a new disease,” Dr. Wu said. “There is a new study that says immunity lasts at least six months, but I believe robust immunity will last at least a year or longer.”

He said to expect “repeated studies” investigating immunity in the upcoming months. He also said booster shots will likely be required in the future, much like people receive regular flu vaccines for protection against that infection.

“These viruses mutate and the stronger ones predominate, replicate better and transmit better,” he said. “I think we’re going to need a booster, the question is when. Maybe in a year.”