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Nearly 70 percent of eligible San Francisco residents are fully vaccinated against COVID-19. Scott Strazzante/The San Francisco Chronicle/Getty Images
  • San Francisco and Seattle have become the first U.S. cities to achieve herd immunity vaccination levels against COVID-19.
  • Officials say the cities reached this milestone by establishing mass vaccination sites, going into targeted neighborhoods with the vaccines, and educating the public about the importance of getting inoculated.
  • Experts say herd immunity across the United States will be difficult to reach due to low vaccination rates in some states.

Seattle’s mayor has proclaimed that her city is the first metropolis in the United States to reach vaccine-induced herd immunity against COVID-19.

Mayor Jenny Durkan made the announcement a week ago. She said 70 percent of Seattle residents 12 years old and older are fully vaccinated, and 78 percent have had at least one shot.

Two days later, San Francisco Mayor London Breed announced that her city had also reached a major milestone. She said that 80 percent of eligible San Franciscans had received at least one COVID-19 vaccine, and nearly 70 percent were fully vaccinated.

In San Francisco, experts credit the city’s efforts to take the vaccine directly to the people who need it most.

“It’s the hub and spoke model,” said Dr. Monica Gandhi, MPH, an infectious disease physician at the University of California-San Francisco.

“The hub is the mass vaccination sites. Everyone who wants a vaccine goes there,” she told Healthline. “The spoke is going out into communities.”

Gandhi said teams targeted neighborhoods, this week taking the Johnson and Johnson single-shot COVID-19 vaccine into vulnerable communities.

“We have community pharmacies, community messaging. It’s that kind of hard work, bringing it to people locally,” she said.

In Seattle, one expert says the city benefits from a multitude of research and medical facilities. There’s also a low level of vaccine hesitancy among the public.

“I think it’s a combination of an affluent, more educated, and aware population,” said Ali Mokdad, PhD, a professor of health metrics sciences at the Institute for Health Metrics and Evaluation (IMHE) at the University of Washington in Seattle.

“And most importantly, they had trust in the government and health officials,” Mokdad told Healthline. “It’s not true, unfortunately, for the rest of the state, so we have some work to do.

“People move around. The airport is in Seattle, major universities are in Seattle, so people come and go frequently,” he noted. “If they’re not vaccinated, they could be carrying the virus and spreading the virus.

“We are in this together, interconnected… and unless we are all safe, none of us is safe,” Mokdad added.

According to the Centers for Disease Control and Prevention (CDC), more than 146 million people in the United States are fully vaccinated.

That’s about 44 percent of the total population, far from the 70 percent some scientists say we would need to meet the herd immunity threshold.

When you look at individual states, the latest stats show Mississippi at the lower end, hovering around 28 percent.

In Georgia, officials have told federal authorities to send 3 million vaccine doses allotted for their states to other places because demand is so low.

Mokdad says that’s a big problem as states are opening back up.

California, the first state to shut down, reopened on June 15, with few restrictions left in place. The unvaccinated are asked to wear a mask still, but it’s all on the honor system.

“It’s summer, cases are coming down everywhere. Everything looks good around you. People are out and about. No more mask mandates. And there’s no incentive to get the vaccine,” Mokdad explained.

In a March 3 article in the Journal of the American Medical Association, Dr. Christopher J. L. Murray, the director of the IHME, wrote that it’s not likely the United States will reach herd immunity, in part because at least a quarter of the population will decline to get vaccinated.

He says that once winter approaches with the new variants of the coronavirus spreading, we could see a return of surge in new cases among unvaccinated people, although not as large as last year.

“The public and health systems need to plan for the possibility that COVID-19 will persist and become a recurrent seasonal disease,” Murray wrote.

Gandhi says San Francisco’s high immunity threshold likely means it would not be as vulnerable to case surges passed on by visitors from out of town.

She expects the city could follow Israel’s path.

“The issue is you have to open up and test the system, which we are doing,” she said, “and make sure hospitalizations don’t go up.

“What we saw in Israel, where they did open up, they mixed and mingled the vaccinated and unvaccinated, and their cases didn’t go up,” she explained.

Gandhi and Mokdad agree states should keep up the giveaways, money, and prizes to encourage more people to get vaccinated.

“Incentives always help. It helps people who are on the fence get the vaccine,” Gandhi said.

“We need to keep an eye on what’s working here and keep pushing it,” Mokdad said. “Whatever it takes to get the public vaccinated, we need to do it.”