With Covid-19 cases showing no signs of abating, several infectious disease experts say that reinfections are likely to become more frequent in the future—with people potentially seeing several infections a year, much like the common cold, Apoorva Mandavilli writes for the New York Times.
Contrary to what health experts initially believed, Covid-19 reinfections are relatively common, and they have grown in number after the emergence of omicron and its subvariants, which have the ability partially evade immunity.
According to a study from the United Kingdom, reinfections in the country were 10 times higher during the recent omicron surge than the delta surge in 2021. People who were unvaccinated, younger, and living in "more deprived" areas were at the highest risk of reinfection between July 2020 and March 2022. In addition, people who had a mild first infection with a low viral load had a higher risk of reinfection.
Although physicians and health agencies say that most people are protected from a Covid-19 reinfection for at least 90 days, there is growing evidence that people can be reinfected much more quickly.
For example, a CDC report from April identified 10 people, including eight children and two adults, who had tested positive for both the delta and omicron variant within 90 days. The interval between the two infections ranged from 23 to 87 days, with a median of 54.5 days.
For healthy individuals, Covid-19 reinfections are typically mild, but health experts warn that some reinfections may result in more severe symptoms.
"On average at a population level, the people who get reinfected have milder symptoms," said Francois Balloux, an infectious disease epidemiologist and director of the UCL Genetics Institute. "That doesn't mean that some people might not have a worse infection the second or even third time."
In addition, some health experts have voiced concerns about how reinfections could affect people's risk of developing long Covid. "I don't think we should make any bets on someone who has a reinfection having a less likelihood of having long Covid," said Amy Duckro, an infectious disease specialist with Kaiser Permanente.
According to some infectious disease researchers, Covid-19 reinfections are likely to become more common as time goes on and different variants continue to circulate—with some people potentially seeing third or fourth reinfections within a year.
"It seems likely to me that that's going to sort of be a long-term pattern," said Juliet Pulliam, an epidemiologist at Stellenbosch University in South Africa. "The virus is going to keep evolving. And there are probably going to be a lot of people getting many, many reinfections throughout their lives."
Separately, Kristian Andersen, a virologist at the Scripps Research Institute, said if we continue to manage the coronavirus the way we do now, "most people will get infected with it at least a couple of times a year."
Although many experts originally believed the coronavirus would behave similarly to influenza, which typically has a large outbreak during the colder months, it has more in common with common cold coronaviruses that cause illness year-round. According to Jeffrey Shaman, an epidemiologist at Columbia University, his team "saw people with multiple infections within the space of a year" when studying common cold coronaviruses.
If Covid-19 reinfections become more frequent, the coronavirus "is not going to be this wintertime once-a-year thing," Shaman said, "and it's not going to be a mild nuisance in terms of the amount of morbidity and mortality it causes."
Although Covid-19 vaccines continue to provide protection against severe illness, their effectiveness against reinfection, particularly with the currently circulating omicron subvariants, appears to be limited, Mandavilli writes. In addition, the different omicron subvariants vary enough genetically that being infected with one does not provide much protection against the other subvariants, particularly after a few months.
To keep up with the coronavirus as it evolves, some health experts believe the Covid-19 vaccines need to be updated frequently, perhaps even more frequently than the annual flu vaccines. According to these experts, even an "imperfect match" to a new coronavirus variant will still offer people some protection and improve their overall immunity against the virus.
"Every single time we think we're through this, every single time we think we have the upper hand, the virus pulls a trick on us," Andersen said. "The way to get it under control is not, 'Let's all get infected a few times a year and then hope for the best.'" (Mandavilli, New York Times, 5/16)
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