Authors: Madison Muller, May 13,2022 Bloomberg News

As a stealth wave of Covid makes its way across the U.S., those who have so far evaded the virus are now falling ill — while others are catching Covid 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 rise of at-home tests, which rarely make it into official case numbers, have made keeping accurate count of positive cases impossible. Additionally, many U.S. states and jurisdictions are now reporting Covid data only sporadically to the Centers for Disease Control and Prevention. Earlier this week, Washington, D.C., reported case data to the agency for the first time since April.This has happened just as new, more contagious subvariants of omicron are making their way through the U.S. population, leading not only to rising first-time Covid cases but also frequent reinfections. The latest versions of the virus appear particularly adept at evading the body’s immune response from both past Covid infections and vaccines. Studies suggest most reinfection cases aren’t even being reported, giving little insight into how often they occur. All this makes it especially difficult to gauge what percentage of the population is presently vulnerable to Covid — and how the pandemic might evolve. “The reality is that things are really not going well at the moment,” said Jacob Lemieux, an infectious disease doctor at Massachusetts General Hospital, speaking at a Harvard Medical School Covid briefing on Tuesday. “We all thought that we were in for a reprieve after the devastating omicron wave. And that was clearly the case until a few weeks ago.”The result is that coworkers are calling in sick, friends are posting snapshots of positive Covid tests on social media and school contact tracing programs are blasting out exposure alerts, even as official Covid case counts suggest the numbers are only creeping back up slowly. On Tuesday, the CDC reported more than 98,000 new cases. The true number is almost certainly higher. “There’s so much less visibility about what’s happening,” said Rick Bright, a virologist and CEO of the Rockefeller Foundation’s Pandemic Prevention Institute.Experts say that it’s difficult to know what the next few months will bring. While vaccines are still doing a good job at keeping most people out of the hospital, the virus is not behaving the same way it has in the past and the majority of the country is living like the pandemic is over. In December and January, during the first wave of omicron infections, case levels skyrocketed before dropping almost as quickly. That’s because widespread infections at the start of the outbreak soon gave the virus fewer people to infect. Public health measures, like masking, also helped reduce the spread. That may not be what happens this time.

“It’s likely that we won’t see the same fast downturn of cases we’ve seen in other surges,” said Bob Wachter, chief of medicine at the University of California, San Francisco.Early evidence suggests omicron has not only made Covid reinfection more likely, but also shortened the window in which a past infection provides protection against the virus. There was hope that the hundreds of thousands of omicron infections this past winter would help bolster population immunity and protect against future surges in coming months. According to CDC data, about a third of the country had caught Covid prior to the omicron wave, a figure that has since increased to more than half. But how effective those antibodies are is now dependent on what variant a person gets.

Delta immunity, for example, doesn’t hold up well against other variants, according to a study recently published in Nature. And there is now evidence that some omicron subvariants can even evade the immune defenses imparted by omicron variants that came before them. One 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 get past the defenses of immunity from 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.There are just too many holes in the data to be able to judge the state of the pandemic accurately. It’s unclear how frequently reinfections are occurring or which variants people are getting reinfected with. The CDC’s last update on reinfections was in January. The agency has not indicated whether it is tracking the cases and does not make such data available to the public.A handful of state health departments, though, have taken to diligently monitoring the repeat cases. That data suggests reinfections are now happening more frequently.The Colorado State Health Department, for example, has recorded more than 44,000 reinfections throughout the pandemic — 82% of which have occurred since omicron became the dominant variant in December. Reinfections are more common among the unvaccinated, but more than a third have happened to people who have completed their initial two-dose vaccine series, according to the data. Over 16% of reinfections in Colorado have been in people with at least one booster dose.Data from the North Carolina Department of Health and Human Services show reinfections in the state have been increasing since late March. Reinfections currently make up 8% of the state’s total infections for the week ending April 30. Repeat infections have been on the rise in Indiana, too, according to data, 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 report from Washington state published Wednesday shows that some reinfections are also leading to hospitalization. The age group most likely to get reinfected is 18 to 34 year olds, but people 65 and older are the most likely to get hospitalized after reinfection, the data show.“It feels 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 getting Covid,” said Wachter, at University of California, San Francisco. “We’re unquestionably in a surge.”