The novel coronavirus (COVID) has infected 94% of people, with the result that the population is now more immune than it was a year ago

It is estimated that 94% of people in the United States have been infected with the COVID-19 virus at least once, according to a new paper from researchers at the Harvard School of Public Health.

What is the main reason behind the sudden increase? The omicron variant case rates broke records early this year and the average boost rates didn’t quite do what the experts had hoped to see.

While this isn’t good news, there is a silver lining: As of early November, the percentage of people with some protection against new infections and severe disease was “much higher than it was in December 2021,” according to the authors.

“Going forward, we’re probably in better shape than we have been,” said Dr. Peter Chen Hong, a professor of medicine at the University of California San Francisco who specializes in infectious diseases and was not involved in the study. But that doesn’t mean that COVID is less prevalent than before or that you are less likely to catch it. In fact, cases are on the rise again, public health officials warn.

A preliminary version of the paper, which has not been peer-reviewed, was published this week on a website called MedRxiv. The results contain uncertainties because they are based on a CDC statistical analysis of reported diagnoses, hospitalizations and vaccinations, rather than antibody testing of a representative sample of Americans.

The team estimated that 29.1% of Americans have been vaccinated and infected, 55.7% have been vaccinated and re-infected, 2.4% are not vaccinated and infected, and 7% are not vaccinated and infected. Of those who have never been infected, 3.5% are vaccinated and 2.1% are not.

Protect populations from infection and severe disease from the Omicron variant in the US population between December 1, 2021, and November 9, 2022, depending on exposure status and regression scenario.
Protect populations from infection and severe disease from the Omicron variant in the US population between December 1, 2021, and November 9, 2022, depending on exposure status and regression scenario.

Researchers from Harvard, Yale and Stanford set out to understand how immunity to the virus has changed since December 2021. The calculations examined the “competing effects” of vaccines, new infections and diminished immunity from them.

They compared the situation from November 2022 to 11 months before that and took into account the fluctuating spread of COVID over time and geography, the extent and speed of fading immunity, re-infection, vaccination status, and the effectiveness of those shots.

In December 2021, 59.2% of people had the COVID-19 virus, by their estimates.

Between December 1, 2021, and November 9, 2022, protection against new omicron infections increased from 22% to 63% nationwide, and protection against omicron infections leading to severe disease increased from 61% to 89%. Analysis found.

The authors warn that “despite the high level of protection at the beginning of winter 2022-2023, the risk of reinfection and subsequent severe disease remains”. They warn that the introduction of “a more transmissible (sub)immune variant or evasion, changes in (human) behavior, or continued waning of immunity” could alter the calculations.

The study estimated that in less than a year there were 116 million first infections in the country and 209 million infections, almost all of them sub-variants of Omicron.

Graph showing the number of people in the United States who have different levels of immunity to COVID, comparing December 2021 to November 2022.

As the virus mutates, so does our understanding of how population immunity affects the spread of COVID.

The researchers found that during each year of the pandemic, the largest spikes occurred in California during the winter holidays, but the fact that so many people contracted the coronavirus earlier this year means fewer people may be at risk this holiday season. At the beginning of this year, Omicron’s first wave broke all previous case records, sickening millions, but also raising the population’s immunity level, at least for a while.

Even with high levels of immunity, COVID is still a deadly virus.

“We still have an incredible number of deaths per day in the United States,” Chen Hong said, “which is even more impressive considering that this is ‘quiet.’”

California’s weekly deaths from COVID have remained below 200 deaths each week so far this month, a far cry from the more than 3,779 deaths reported in one week in early January 2021.

It’s a significant improvement, but “there’s nothing to celebrate about,” Chen Hong said, noting that the virus remains a leading cause of death in the country. “We can do better.”

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