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Florida had a shot at herd immunity. Now it’s slipping away.

The delta variant, vaccine hesitancy and lifted safety measures put immunity goals in jeopardy.
Nurse practitioner Paula Joseph, of Tampa, draws a dose of the Pfizer-BioNTech COVID-19 vaccine on April 15.
Nurse practitioner Paula Joseph, of Tampa, draws a dose of the Pfizer-BioNTech COVID-19 vaccine on April 15. [ DOUGLAS R. CLIFFORD | Times ]
Published Jul. 8

Herd immunity may be slipping further and further out of reach.

President Joe Biden set an aspirational goal to immunize 70 percent of the adult population against the coronavirus by July 4. But Independence Day came and went, and 33 percent of U.S. adults still haven’t received a single vaccination shot.

In Florida, 65 percent of adults have been at least partially vaccinated, and 56 percent have been fully vaccinated.

Public health experts say the White House set that goal under optimistic conditions: continued social distancing, a rapid vaccine rollout and the absence of a highly infectious variant of the COVID-19 virus.

Now all three factors have changed for the worse:

  • The delta variant is more infectious and dangerous, and is spreading quickly.
  • Large pockets of the population remain stubbornly unvaccinated, and partial vaccination isn’t good enough against the delta variant.
  • Mask and social-distancing orders may have been lifted too soon, accelerating the spread among the unvaccinated.

“Conditions on the ground have changed,” said Dr. Michael Teng, a virologist at the University of South Florida. “Every time we have a more transmissible variant, the number of people that need to be fully vaccinated to get to herd immunity goes up.”

Experts no longer fear large outbreaks. But the delta variant could fuel mini outbreaks in low-vaccinated areas. So as long as the coronavirus continues to circulate, it will continue to infect, sicken and kill thousands of Americans, primarily the unvaccinated and immunocompromised.

• • •

Recent estimates from the Centers for Disease Control and Prevention show the delta variant is now the dominant strain in the United States, and is spreading fast in Florida.

The CDC data, released earlier this week, shows that the delta variant accounts for 13.2 percent of new coronavirus cases in Florida, as of June 19. That’s up from 2.3 percent as of June 5.

Tracking data from the Florida Department of Health indicates that the delta variant is present in 34 Florida counties, including Hillsborough, Pinellas, Pasco, Hernando, Polk and Citrus counties, as of June 29.

Related: The coronavirus variants: What you need to know

The delta variant may be as much as 50 percent more infectious, according to a Public Health England report published last month. This means the virus will spread faster, especially among unvaccinated individuals.

It may also be harder to prevent infection using vaccines developed to inoculate against the previous strain. One recent study found that the Pfizer vaccine is only 33 percent effective among people who have had only the first of the two-part vaccination.

That’s a concern in Florida where about 10 percent of the adults are only partially vaccinated. As the delta variant continues to spread, it’s troubling to see so many people apparently skipping out on their second dose, said Jason Salemi, who teaches epidemiology at the University of South Florida’s College of Public Health.

“That might mean that we’re not doing as good a job of turning out people, if they’ve gotten Moderna or Pfizer, to complete the series,” Salemi said. “And I think that’s a real problem, and maybe more of a problem in Florida than it is elsewhere.”

• • •

The statewide lifting of mask mandates and social-distancing measures compounds the new risk posed by the delta variant, experts say.

Such measures were used to slow infection rates when vaccines were unavailable. But now there is no mechanism to keep unvaccinated people from packing into bars and restaurants and transmitting the virus. Allowing a highly infectious disease to continue to spread allows the coronavirus to linger, putting the goal of herd immunity further out of reach.

Epidemiologists such as Thomas Hladish, a research scientist at the University of Florida’s Emerging Pathogens Institute, like to think of herd immunity as a continuum. A mutating virus and adapting human behavior constantly change the level of vaccination needed to prevent another epidemic breakout, they say.

“In a simple epidemiological world, where you have one variant that’s not mutating and a vaccine that works the same way for everyone, then, basically, yes, there’s a magical number,” Hladish said. “In the real world, people’s behaviors are dynamic. If they feel safer, they interact more.

“In that scenario, you need substantially more people vaccinated, because the chances of an infected person finding that one last susceptible person out there go up when you have more and more interactions.”

Related: Vaccine hesitant? We want to hear from you.

Gov. Ron DeSantis issued an order May 3 suspending local mask mandates statewide, but it does not prohibit businesses from requiring masks. Since then, most bars, shops and restaurants have adopted the CDC guidelines that say fully vaccinated people no longer need masks in most settings.

Experts worry that unvaccinated individuals don’t appear to be taking precautions to protect themselves and others. The CDC recommends that unvaccinated individuals wear a mask in public.

“I’m not very convinced that that’s happening,” said University of Florida epidemiologist Cindy Prins. Despite low vaccination rates among some groups, she said, it’s rare to encounter anyone wearing a mask, even in crowded settings.

New infections and hospitalizations have increased in recent weeks as the delta variant spreads. Nearly 16,000 new coronavirus cases were detected in Florida last week, a 35 percent increase over the week before. Florida also saw 1,963 new hospitalizations from June 27 to July 4, an increase of 18 percent.

“We have done this throughout the pandemic,” Prins said. “We rushed ahead without letting cases get low enough, without letting the vaccines get rolled out far enough.

“We throw away these precautions at a time when it’s probably too early to do so. And yet, we don’t seem to learn that lesson.”

• • •

Over 65 percent of Florida adults have been vaccinated, but the vaccination rate is not uniform across the state.

State data shows highly-vaccinated areas next to ZIP codes where fewer than one-in-four residents have been vaccinated.

“It doesn’t matter if 70 percent of the population is vaccinated, if the other 30 percent is getting together and having parties,” said Hladish.

Unvaccinated people tend to be concentrated in certain areas and bunched among certain age groups and political ideologies.

State data shows that one-third of Florida residents between the ages of 12 and 30 have been vaccinated. And a recent survey conducted by the University of South Florida found that Floridians who identify as Republican or Independent are about 20 percent less likely to be vaccinated than Democrats. A Tampa Bay Times analysis of ZIP code data also shows that areas with higher concentrations of residents who are Black or living in poverty tend to be less vaccinated.

“The same people who are going to be less cautious about getting together, having parties indoors or whatever, are the same people in many cases who are less inclined to get vaccinated,” said Hladish. “There is a big irony there, because those are the people who most need to get the vaccine.”

• • •

Still, there are reasons to be optimistic, said Dr. Amesh Adalja, who researches pandemic preparedness at Johns Hopkins University.

“The whole reason that COVID-19 is a public health emergency is because of its ability to cause serious disease, hospitalization and death at such a rate that we saw hospitals go into crisis,” said Adalja.

High vaccination rates among the elderly, with 83 percent of Floridians over 65 vaccinated, goes a long way to curbing high hospitalization and death rates that plagued hospitals nationwide early in the pandemic.

Continued transmission of the virus will cause illness among unvaccinated and immunocompromised populations, “but is it going to lead to hospitals worrying about their ability to care for patients?” said Adalja. “I don’t think so.”

Other health experts are not so optimistic, pointing to long-term complications and lowered life expectancy due to the virus.

The risk now, they say, is among unvaccinated individuals who continue to take risks in their daily lives.

“The coronavirus is still causing thousands of cases a week in Florida,” said Derek Cummings, an epidemiologist at the University of Florida. “So if you’re not vaccinated, you can’t really outrun it. Sooner or later you will get exposed to the virus.”

• • •

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