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Natural vs. vaccine immunity and what a disease immunologist says about the science

vaccine
Posted at 9:49 PM, Nov 05, 2021
and last updated 2021-11-05 23:19:57-04

CLEVELAND — We’ve heard many questions come up in the last several months about natural immunity and whether it’s enough to protect those who have it from COVID-19, in lieu of a vaccine.

The topic came up last month at the Ohio Statehouse, where some lawmakers tried to get “natural immunity” added as an exemption to vaccine mandates.

Dr. Mark Cameron, a disease immunologist at Case Western Reserve University, spoke with News 5 on Friday to answer questions about natural immunity, vaccine-mediated immunity and what all of this means for individuals and their physicians.

Cameron said the number of new COVID-19 daily cases in Ohio has been coming down for a while.

“We're winning the skirmishes, I would say, against this virus at the moment. But are we winning the war ultimately?” Cameron said, noting that flu season coming up poses additional complications.

He started with some definitions of phrases we’ve all heard thrown around.

“Natural immunity refers to being infected with COVID-19 and going through the disease process and clearing the virus, gaining a level of immunity over it,” Cameron said. “Also in the short term, we don't know how long with COVID-19, being immune to reinfection for a certain length of time.”

“A natural infection and gaining immunity to COVID-19 by having it before certainly provides your immune system with enough instruction, enough education to avoid reinfection with COVID-19 again,” he added.

All of this is different from (but works the same as) “vaccine-mediated” immunity, “where you gain that immunity through the shot, through the vaccine.”

Cameron said there is a similar mechanism for your body between natural immunity and immunity gained by the vaccine, even though you’re getting it a different way.

“This is a means of preventing reinfection through neutralizing antibody levels to the spike protein, and that blocks, as long as they're present and you know, plentiful enough, that blocks the virus from getting back into your cells and making you sick,” Cameron said.

The standard test by which to check levels of someone’s antibodies to anything (a viral infection, a vaccine, etc.) is to do a titer check, “where they actually test levels of antibodies against a given infectious agent.”

With COVID-19, Cameron said, since there could be a natural infection from other types of coronaviruses, those antibody tests may not be entirely clear.

“Even if we can be very specific to the coronavirus that causes COVID-19, we don't yet know what the particular levels are required to be successful in blocking it in the future,” Cameron said. “It varies very greatly between individuals, and it also varies over time as we are coming fully to grip now in this idea of waning immunity.”

“Waning immunity,” Cameron cautioned, doesn’t mean your immune system can’t “reboot” and help you recover from reinfection by COVID-19. But he said COVID-19 is “very good at getting in and getting ahead of our immune system and infecting us,” so we need “high levels of neutralizing antibodies so that the virus barely gets a chance to enter our cells.”

OK — so there are a lot of questions to which we still don’t have answers. Such as, if someone has already had COVID-19, what’s the long-term risk of getting it again? Or, if they’re vaccinated and get a breakthrough case, can we say if their immune system responded to the vaccine in the first place?

“However we gain immunity to COVID-19, our immunity drops over time. That really is dependent on that neutralizing antibody level and whether we got COVID-19, whether we had the full vaccine regimen, whether we had both conditions, we will need a boost as well over time,” Cameron said.

He emphasized it is hard to come up with a common piece of advice that covers everyone.

“I certainly understand those concerns and really that comes down to yourself and your physician,” Cameron said. “There may be very good reason, you know, in consulting with your doctor why you wouldn't get a boost now or you wouldn't get the vaccine right now if you indeed didn't have it, you know, in the past. And that could be because you had COVID-19 very recently. It could be that you're sick with another infectious disease and your immune system is already activated. Or it can be the opposite where somebody is immunosuppressed or they are on cancer treatments and other type of therapies where your immune system is essentially kicked when it's down.”

All of these, he said, are important considerations to take up with one’s doctor. However, he was clear that the overall science supports getting a vaccine even if you have natural immunity from COVID-19 already.

“Natural infection by COVID is is certainly not a safe way to gain immunity to this virus. And really, I would say that risking reinfection isn't either,” he said.

He added, “We are more prepared than ever to clear this infection or at least stop it from hurting and killing us like it has in the past.”

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