There is some anecdotal evidence that people can catch Omicron twice, and possibly become infected with the new BA.2 Omicron subvariant shortly after catching the original BA.1 strain. But scientists caution that such reinfections appear rare, especially over a short period of time, and may be overestimated as a result of confusion over testing.
As governments shift to “living with the virus,” the potential for Omicron to reinfect recovered COVID patients could alter the duration and endgame of the Omicron-fueled COVID surge. But evidence so far suggests reinfections are so rare that they should not disrupt officials’ plans to reopen economies and drop mask mandates and other social distancing measures as record-high COVID caseloads start to recede.
“People are being reinfected immediately again after Omicron infection,” Yaneer Bar-Yam, president of the New England Complex Systems Institute, wrote on Twitter. Yaneer pointed to both anecdotal evidence of reinfection cases and a new preprint medical study indicating that immunity from Omicron infections may not be as strong as immunity from other variants like Delta.
But scientists believe that reinfections may be occurring at higher rates when people have asymptomatic or mild cases in their first Omicron infections.
“Yes, you can get Omicron twice,” Stanley Weiss, an epidemiologist at Rutgers School of Public Health, told Yahoo, citing discussions with colleagues in South Africa. “If you had a mild infection, didn’t get a very good immune response, and you get exposed again with a big dose of the virus, it’s definitely possible,” he said.
In late January, Dr. Anthony Fauci, the White House’s chief medical adviser, acknowledged that while possible, reinfections with the same variant are extremely rare.
“Sure, there are reinfections. But it is unlikely that if you mount a good immune response—at least over a period of several months—it is extremely unlikely that you will be reinfected with the same variant,” Fauci told reporters. The data also suggests that COVID reinfections are generally mild, no matter the strain. In December, researchers in Qatar found that those reinfected with any variant of COVID-19 were 90% less likely to be hospitalized than people with their first infections.
But it’s unclear how soon people can be infected with the Omicron BA.2 subvariant, a cousin of Omicron’s original BA.1 strain, after catching BA.1.
In Israel, researchers recently found a handful of individuals who appeared to contract the BA.2 strain of Omicron after getting infected with BA.1.
“We [have] received some…reports that in very rare occurrences so far, people that…were infected with Omicron could also…be infected with BA.2,” professor Cyrille Cohen, head of the immunotherapy lab at Israel’s Bar-Ilan University, tells Israel’s i24 news station.
But Dr. Sharon Alroy-Preis, head of public health services at Israel’s Health Ministry, rejected the report’s findings to Israeli media last week, saying that Israel was not aware that “such a case” existed. Alroy-Preis said that it was extremely unlikely for someone recently recovered from one strain of Omicron to immediately be infected with another because “the antibodies that helped [a patient] recover” would protect the patient from reinfection.
Scientists may soon have more data on BA.2 since the Omicron strain appears roughly 34% more infectious than Omicron’s initial BA.1 strain and is outcompeting BA.1 in places like Denmark, South Africa, and the U.S.
But some researchers caution that people may overestimate the likelihood of reinfections as a result of testing complications.
The U.S. Centers for Disease Control and Prevention defines reinfection as an infection that happens after someone has gotten the disease, recovered, and then tested positive more than 90 days after the first infection. The definition reflects the fact that people can test positive for weeks or months after they are infectious or symptomatic, Dr. Shira Doron, hospital epidemiologist at Tufts Medical Center, told NBC’s Boston affiliate.
She explained that among patients with a low viral load, PCR tests, which are highly accurate and used in clinical settings, often detect infections that quicker, less precise rapid antigen tests miss. The testing differences mean that patients may think they have been reinfected with COVID when really they have a lingering viral load from their initial infection.
“It’s possible that you have COVID and you test positive, and then you get another cold and you do a PCR again—we see this all the time,” Doron said. “So I think there are some falsely labeled reinfections, although, you know, time will tell whether we are seeing true Omicron reinfections.”
For its part, the U.S. CDC says it is not necessary for those infected with COVID to get a negative PCR test result before they resume their normal lives. Rather, the U.S. CDC says that COVID-19 patients should self-isolate for five days after COVID-19 symptoms subside or after detecting an asymptomatic infection, followed by five days of wearing a mask when around others.
Fauci said this week that even as the U.S. battles a record wave of infections the country is on its way out of “the full-blown pandemic phase of COVID-19.” He said he does not believe that reinfections pose a risk toward a return to normalcy.
“I hope we are looking at a time when we have enough people vaccinated and enough people with protection from previous infection that the COVID restrictions will soon be a thing of the past,” Fauci said.
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