As a stealth wave of COVID-19 makes its way across the United States, those who have so far escaped the virus are now falling ill – while others catch COVID-19 for a second, third or even fourth time.
Several factors have conspired to make the state of the pandemic harder than ever to track. The increase in home testing, which rarely figures in official case counts, has made it impossible to accurately tally positive cases. Additionally, many US states and jurisdictions now only report COVID-19 data sporadically to the Centers for Disease Control and Prevention. Earlier this week, Washington, DC reported case data to the agency for the first time since April.
This happened just as new, more contagious subvariants of omicron are making their way into the US population, leading not only to an increase in early cases of COVID-19, but also to frequent reinfections.
The latest versions of the virus seem particularly adept at evading the body’s immune response to both previous COVID-19 infections and vaccines. Studies suggest that most cases of reinfection go unreported, giving little information about how often they occur.
All of this makes it particularly difficult to assess what percentage of the population is currently vulnerable to COVID-19 – and how the pandemic might evolve.
“The reality is that things are really not going well right now,” said Jacob Lemieux, an infectious disease physician at Massachusetts General Hospital, during a Tuesday briefing on COVID-19 from Harvard Medical School. “We all thought we were going to get a reprieve from the devastating wave of omicron. And that was clearly the case until a few weeks ago.
The result is co-workers calling in sick, friends posting snapshots of positive COVID-19 tests on social media, and school contact tracing programs broadcasting exposure alerts, even as the official number of COVID-19 cases suggests that the numbers just crawl back slowly.
On Tuesday, the CDC reported more than 98,000 new cases. The actual number is almost certainly higher. “There’s so much less visibility into what’s going on,” said Rick Bright, virologist and CEO of the Rockefeller Foundation’s Pandemic Prevention Institute.
Experts say it’s hard to know what the next few months will bring. While vaccines are still doing a good job of keeping most people out of hospital, the virus is not behaving the same way it has in the past and the majority of the country is living like if the pandemic was over.
In December and January, during the first wave of omicron infections, case levels soared before falling almost as rapidly. Indeed, widespread infections early in the outbreak quickly gave the virus fewer people to infect. Public health measures, such as masking, have also helped reduce the spread.
That may not be what will happen this time.
“It’s likely we won’t see the same rapid decline in cases that we’ve seen in other outbreaks,” said Bob Wachter, chief of medicine at the University of California, San Francisco.
Early evidence suggests that omicron not only made COVID-19 reinfection more likely, but also shortened the window in which past infection offers protection against the virus.
It was hoped that the hundreds of thousands of omicron infections last winter would help boost people’s immunity and protect against future outbreaks in the coming months. According to CDC data, about a third of the country had caught COVID-19 before the omicron wave, a figure that has since risen to more than half. But the effectiveness of these antibodies now depends on the variant a person gets.
Delta immunity, for example, does not resist well against other variants, according to a study recently published in Nature. And there is now evidence that some omicron sub-variants can even evade the immune defenses conferred by the omicron variants that preceded them. A recent study published as a preprint by researchers in Beijing found that several omicron subvariants – BA.2.12.1, BA.4 and BA.5 – could overcome immunity defenses against infection. with another version of omicron, BA.1.
All of these factors mean that huge swaths of the population once protected from infection may now be vulnerable.
It is not known how often reinfections occur or with what variants people are reinfected. The CDC’s last update on reinfections was in January. The agency has not said whether it is tracking cases and does not make this data available to the public.
A handful of state health departments, however, have begun to diligently monitor repeat cases. These data suggest that reinfections are now occurring more frequently.
The Colorado State Department of Health, for example, has recorded more than 44,000 reinfections throughout the pandemic, including 82% since omicron became the dominant variant in December. Reinfections are more common in unvaccinated people, but more than a third have happened to people who have completed their initial series of two-dose vaccines, the data shows. More than 16% of reinfections in Colorado have occurred in people who received at least one booster dose.
Data from the North Carolina Department of Health and Human Services shows that reinfections in the state have been increasing since late March. Reinfections currently represent 8% of the state’s total infections for the week ending April 30.
Repeat infections have also increased in Indiana, the data shows, where they account for more than 12% of total cases, and in Idaho where they accounted for 18.5% of cases in the first quarter of 2022.
A Washington state report released Wednesday shows that some reinfections also result in hospitalization. The age group most likely to be reinfected is 18 to 34, but people 65 and older are the most likely to be hospitalized after reinfection, the data shows.
“It’s like the first time in two years that no matter if someone is really careful and does everything right, it won’t be surprising if they end up contracting COVID-19,” said Wachter, of the University of California at San Francisco. “We are definitely in full swing.”
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