Busting the myths that surround herd immunity
RALEIGH, N.C. (WNCN) — It seems simple enough to grasp: Protecting more people from COVID-19 — either by exposure or inoculation — makes it harder for the coronavirus to spread.
And yet …
“Herd immunity is a highly misunderstood concept,” said Dr. Lavanya Vasudevan of the Duke Global Health Institute.
Reaching herd immunity, when enough people are immune to the virus and it can no longer easily jump from person to person, has become the goal. Pinpointing its exact threshold for COVID-19 has been difficult because it depends on how infectious the disease is. Opinions from experts range from 67 percent to 80 percent.
“Everybody wants to know, when can we go back to normal, right?” said Dr. Julie Swann, an expert in vaccine distribution at North Carolina State University. “And sometimes people talk about herd immunity as, as a way of getting back back to normal.”
But misconceptions abound about it.
Reaching the appropriate herd immunity threshold is not the point where it’s safe to stop vaccinating people, Vasudevan said. Nor is it the time when the disease simply disappears.
“The disease does not vanish overnight,” Vasudevan said. “The number of cases that we see may reduce dramatically, because now more people are protected. But the number of cases does not go down to zero. So that, by itself, is the justification for continuing vaccinations.”
Those levels may differ between parts of the globe, countries, states and regions.
And here in North Carolina, we can only guess how far away that goal is with some very rough math.
MIT data scientist Youyang Gu estimated on his website that about 26 percent of North Carolinians have been exposed to COVID-19, including both those who have never been tested and those lab-confirmed cases reported to the state.
The state Department of Health and Human Services says nearly 19 percent of residents are at least partially vaccinated.
Taking into account some overlap between those groups, we can guess perhaps 40 percent of people in the state have at least some level of protection.
That’s an improvement from where the state was even a month ago — but there’s still a long way to go to reach that threshold.
“One reason to be aware of this … and its importance is that we are not anywhere close to herd immunity right now,” Swann said.
Getting to that point doesn’t just rely on vaccines and exposures, Swann said. The other, more basic things people do — like wearing masks and keeping a safe distance — also play a role.
Another factor: The variants of the virus, which may make it more transmissible or allow for reinfection.
“And so (the reinfection possibility) means that that herd immunity doesn’t doesn’t happen until we get to a bigger number of protection in the population,” Swann said.
What will it look like once herd immunity is reached? Swann says that while infection numbers won’t double nearly as quickly as they did last spring when the pandemic took root, small individual communities could still be vulnerable, although it likely won’t be on a scale large enough to overcrowd hospitals.
“I’m thinking of these as ‘micro-surges.’ They can still be deadly, they can still put people in the hospital, so they are still something to worry about,” Swann said. “But we will have enough healthcare resources on the whole so that our health system is not blowing up from simultaneous demand.”
Ultimately, it’s important to know that while herd immunity is much more significant to an entire population than it is for individual people.
“Relying on others to be vaccinated and relying on this concept of herd immunity is not a great strategy,” Vasudevan said. “The best way to protect yourself is to get vaccinated.”
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