Charlotte is nowhere near COVID herd immunity. Here’s what that will take. 

Coronavirus vaccines are ushering in the long-awaited light at the end of the pandemic tunnel.

But as Mecklenburg enters its third month of immunizations, only 47,442 residents in a county of more than 1 million people have fully traversed that dark passageway — equating to 4.3% of the population receiving both shots.

A higher percentage, 8.4%, are halfway through the tunnel, benefiting from partial protection after one dose, according to vaccination data as of Thursday from the North Carolina Department of Health and Human Services.

Health experts say it will take much of the summer before Charlotte and surrounding towns get close to what many refer to as “herd immunity.” That threshold — potentially 8 of every 10 people vaccinated, by some estimates — is expected to stunt the spread of the coronavirus and provide protection, even for individuals still without inoculations.

“It is not a magic number. It is important to remember it is a gradient,” Amber D’Souza, an epidemiology professor at the Johns Hopkins Bloomberg School of Public Health, told the Charlotte Observer.

“We’re going to begin to see successes the closer that we get to that target threshold ... We will see exponential (case) decreases where things begin to go in the right direction and get under control, but the higher we get the vaccination rates, the better those outcomes are.”

Key findings from recent interviews with experts include:

▪ The exact date for when Mecklenburg County reaches herd immunity is not known and difficult to predict.

▪ Vaccinations and “subgroup” immunity among health care workers may be already helping.

▪ Too many people refusing to get vaccinated is an obstacle to reaching herd immunity.

▪ 2021 will get progressively safer as more people are immunized.

Vaccines and herd immunity

The threshold for local herd immunity could range between 65% to 85%, Mecklenburg Public Health Director Gibbie Harris said at a recent news briefing. The county, she said, has a “long way to go” before residents can comfortably “be out and about in the community.”

This week, Mecklenburg County Public Health and local hospitals will embark on vaccinating teachers and school support staff. Thousands of other frontline essential workers in Group 3 become eligible in March.

Harris said Group 3 poses a challenge since “it’s huge.”

It’s unclear when Group 4, encompassing adults with high-risk medical conditions, will get in line. Under North Carolina’s vaccine prioritization framework, Group 5 is everyone else.

With increasingly wider eligibility, the lurch to herd immunity will quicken, epidemiologists agree. Dr. Anthony Fauci, the country’s top infectious disease expert, expects all adults who want the vaccine will become eligible by late spring or early summer.

But limited supply will continue to dictate speed and availability of the shots.

Once all willing and eager residents are vaccinated, the build to herd immunity will face one more challenge: hold outs who forgo the shots for reasons ranging from systemic distrust in medicine or skepticism about an expedited vaccine development process.

As demand and supply of vaccines balance out, there’s likely to be a large number of people hesitant or opposed to getting the shots. An Elon University poll conducted in late January found one-quarter of North Carolinians aren’t sure if they will get vaccinated.

Michael Thompson, associate chair of the Public Health Sciences department at UNC Charlotte, likens this later phase of the roll-out process to un-popped kernels in a bag of microwave popcorn.

“In terms of herd immunity ... You have one kernel, then it’s popping like crazy,” Thompson said. “Then as you get closer in the cycle, there’s fewer kernels to pop.”

It’s important to realize, experts note, that vaccination rates and the prevalence of COVID-19 could vary by community, state or country in the coming months.

‘Bumpy ride’

People are already wondering whether Easter gatherings will be safe this year — and if getaways over Memorial Day weekend are possible.

Labor Day is the first holiday in 2021 that might be close to “normal” when it comes vaccines, herd immunity and the virus, said David Wessner. The Davidson College biology professor and coronavirus researcher says late summer and early fall offer a stronger glimmer of hope.

For the last five weeks, infection rates have dropped steadily in Mecklenburg and many places across the Carolinas.

Continued improved trends in the coming months would reflect the effectiveness of the vaccines at slowing virus spread. The impact could be potentially amplified from people who have temporary immunity after contracting COVID-19, health experts say.

But new strains of the virus, including the highly contagious UK variant already detected in Mecklenburg and at Davidson College, might require a steeper herd immunity threshold than previously thought. Historically, scientists have found that more transmissible illnesses require higher vaccination rates in order to reach herd immunity.

For instance, to achieve herd immunity against the measles, 95% of the population needs to be vaccinated, according to the World Health Organization. Polio, by contrast, needs a roughly 80% threshold.

Faced with more contagious COVID-19 strains, officials are racing to get people vaccinated before mutations infect more people.

“It’s going to be a really bumpy ride,” Thompson said. “Our best-case scenario is a combination of maximizing our mask-wearing and social distancing while we vaccinate, to keep the (COVID-19) numbers as low as possible by the time we get to herd immunity.”

Subgroup immunity

Before attaining herd immunity, every significant jump in the percentage of people vaccinated makes a difference. In interviews with the Observer, experts said seeing just half of the population protected will drive down hospitalizations and coronavirus-related deaths.

Projections around herd immunity must also factor in the relative effectiveness of different vaccines. The two being administered now are from Pfizer-BioNTech and Moderna. Experts say it is difficult to calculate herd immunity targets when factoring in other vaccines with lower efficacy rates, like Johnson & Johnson’s one-dose regimen that could be approved for emergency use later this month.

Wessner said once vaccination rates reach 85%, there could be a return to “normal.” That is at least six months away — probably longer.

And even then, the virus will still be circulating.

“This isn’t just going to go away. We’re not going to reach whatever the (immunity) level is and we’re done,” Wessner said. “It’s going to be a while that this is with us.”

Consider a trip to the supermarket, where a customer comes into contact with 100 people. If only 10% of the county’s population is immunized, the chances of interacting with someone fully vaccinated there is low. When the percentage ratchets up to about 30% (and subsequently higher), the chances are better — and the grocery haul becomes less risky, Wessner said.

So far in Mecklenburg, healthcare workers and senior citizens have gotten shots.

It creates a sort of subgroup of vaccine recipients, where certain environments — like nursing homes — can operate with more ease and comfort than others, D’Souza said. Fewer COVID-19 outbreaks at long-term care facilities could be a harbinger of progress, she said.

A similar situation is true for doctors and nurses: If there is another surge in hospitalizations, medical personnel would now have their own biological protection, plus personal protective equipment, to mitigate risk. Assuming the vaccination campaign is successful, Mecklenburg should have already seen the worst of coronavirus-induced hospitalizations last month.

“The rates that we experience next winter are not going to be anything like what we had to go through this year,” D’Souza said. “That should be the story next year, but it’s entirely dependent on whether we are able to effectively bring down the rates of infections this spring and summer.”

Enhanced vaccine distribution could mean more opportunities for people to safely socialize — with masks and distancing — and expand their quarantine bubbles. Someone who was fearful of indoor dining the past year may now experiment with risk tolerance, she suggested.

For those who may be near the end of the vaccination line, though, Thompson warns to not let your guard down, even if COVID-19 risks fall this spring.

”We’re so done with it,” Thompson said of pandemic fatigue. “This is kind of the worst possible time for that.

This story was originally published February 22, 2021 at 6:15 AM.