With the U.S. reporting a record high of more than 1 million new COVID-19 cases on Monday, many are wondering if the country could finally reach herd immunity nearly two years into this pandemic.
“There’s been a lot of talk about this being it, the big wave that’s gonna finally get most people infected. It is possible that with this Omicron wave, we will reach a level of herd immunity,” says Dr. Luis Ostrosky, chief of infectious diseases with McGovern Medical School at the University of Texas Health Science Center at Houston.
Israel’s top health adviser, Nachman Ash, agrees, recently saying he believes his country could reach herd immunity based on the surging levels of Omicron infections. “The [infection] numbers will have to be very high in order to reach herd immunity,” Ash, director general of the Health Ministry, said Sunday. “This is possible.”
What the health community refers to as “herd immunity” generally occurs when a large portion of the population is immune, and the virus or bacteria can’t find a host within which it can reproduce. Herd immunity can be achieved by having enough people contract an infection and then build up a natural immunity, or with strong vaccination coverage. Approximately 94% of people must be immune in order to successfully halt transmission, according to the Mayo Clinic.
But the problem with herd immunity, and particularly with the COVID-19 virus, is that it is likely time sensitive, Ostrosky says. “We always start seeing declining antibodies a few months out,” he says. Not only is the immunity conferred time-limited, it may also not protect against other mutations of the coronavirus. “An infection with this particular variant doesn’t guarantee protection against future variants,” Ostrosky says.
As long as COVID-19 is able to mutate, lasting immunity is likely off the table. If yet another mutation or variant of concern surges that more completely evades the antibodies people have built up, “we start all over,” Dr. Gregory Poland, head of the Mayo Clinic’s Vaccine Research Group, said Tuesday.
“So it’s a kind of very risky proposition to be saying: ‘Let’s go for it. Let’s get herd immunity. Everybody gets infected and we’ll be done,’” Ostrosky says.
There is also a very real downside to natural herd immunity, which is that a lot of people are going to get infected and, just by sheer numbers, could end up in the hospital and dying, Ostrosky says. “That’s why we’ve never sort of relied on herd immunity as a strategy to get out of the pandemic. There’s a cost to it,” he says.
“People think, ‘Oh, Omicron, it’s no big deal.’ It is a big deal. If you’re not vaccinated, Omicron is a big deal for you,” Poland says.
For those with a healthy immune system who are immunized and boosted, an Omicron infection is likely to be much more mild than it would be for an unvaccinated person. Now, that doesn’t mean it can’t be transmitted to somebody else who is vulnerable. And the long-term effects of COVID are still a concern. “Getting immunized is basically a weapon against this virus,” Poland says.
Many health experts say the best way to achieve some level of immunity is through vaccinations. As with natural immunity, vaccinated immunity may not last, but the cost will not be as high.
Take influenza, for example, commonly known as the flu. It’s a big respiratory virus that still sees seasonal outbreaks, but there are flu shots developed seasonally to help mitigate the worst of the effects. “That’s what slowly seems to be happening with coronaviruses. It will change and become endemic,” Poland says.
“If you got your flu vaccine this fall, and I hope you did, then you got vaccinated against a variant of influenza that first showed up in 1918. So, a hundred-plus years later, we’re still vaccinating against that,” Poland adds. “One hundred years from now, our great, great, whatever that will be, great grandchildren will be getting immunized against coronavirus.”
“I see Omicron as our kind of final warning shot,” Ostrosky says. If the U.S. doesn’t do something “drastic and permanent,” Ostrosky believes COVID will mutate and produce a variant of high consequence, which means one that is totally resistant to the vaccines, therapeutics, and even detection through currently available testing.
Those drastic measures the U.S. needs to take? Widespread vaccination and mask use, Ostrosky says. He believes the U.S. needs to achieve a minimum threshold of having 60% to 70% of the population vaccinated across all locations, socioeconomic backgrounds, ethnicities, genders, ages, and races.
“Sometimes we see vaccine data saying 90% of the adults are vaccinated, but that doesn’t work when only 20% of the kids are. We need kind of a uniform vaccination rate,” he says.
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