Sixty percent of Americans, including 75 percent of children, had been infected with the coronavirus by February, federal health officials said Tuesday, another milestone in the pandemic that continues to confuse expectations.
The highly contagious version of Omicron was responsible for much of the fee. In December 2021, when the variant began to spread, only half of the people had antibodies showing a previous infection, according to a new study from the Centers for Disease Control and Prevention.
Although the numbers came as a shock to many Americans, some researchers said they expected the numbers to be even higher, given the contagious variants that have passed through the nation over the past two years.
There may be good news in the data, some experts said. Increasing immunity for the whole population may offer at least partial protection against future waves. And this trend may explain why the wave that is now raging in China and many countries in Europe has been silenced in the United States.
The high rate of previous infections may also mean that there are now fewer cases of life-threatening illness or death than infections. “We will see fewer serious illnesses and more and more changes to clinically mild illnesses,” said Florian Kramer, an immunologist at Icahn Medical School in Mount Sinai, New York.
“It will be increasingly difficult for the virus to cause serious damage,” he added.
Administration officials also believe the data portends a new phase of the pandemic, in which infections may be common at times but cause less harm.
Speaking at a news briefing on Tuesday, Dr Ashish Ja, the new Covid White House coordinator, said stopping the infections “is not even a political goal. The aim of our policy must be: obviously to minimize infections where possible, but to ensure that people do not become seriously ill.
The average number of confirmed new cases per day in the United States – more than 49,000 as of Monday, according to the New York Times – is comparable to the levels last seen in late July, even when cases rose more than 50 percent in the last two weeks, a trend that infectious disease experts attribute to new sub-variants of Omicron.
Dr Ja and other officials warned of complacency and called on Americans to continue receiving vaccinations and booster vaccines, saying antibodies from previous infections did not guarantee protection against the virus.
During the Omicron surge, infections rose sharply among children and adolescents, according to a new study. Previous infections have increased the least among adults aged 65 and over who have the highest vaccination rates and are more likely to take precautions.
“Evidence of previous Covid-19 infections has increased significantly in each age group,” Dr Christy Clark, the agency’s researcher leading the new study, told a briefing Tuesday.
Widespread infection raises alarming prospects: a potential increase in cases of prolonged Covid, a poorly understood constellation of long-term symptoms.
Up to 30 percent of people infected with the coronavirus may have persistent symptoms, including disturbing changes in the brain and heart. Vaccination is thought to reduce the chances of long-term Covid, although it is not clear by how much.
“The long-term effects on health are not clear, but they are certainly worth taking very seriously, as some people will struggle with the consequences for a long time,” said Bill Hanaj, an epidemiologist at Harvard TH Chan School of Public. Health.
Even a very small percentage of infected or vaccinated people who develop long-term Covid would translate into millions across the country.
Although the focus is often on preventing the health care system from distorting in the leap, “we must also be concerned that our health care system will be overwhelmed by the current health care needs of the long-term Covid population,” said Zoe McLaren, a health expert. policy at the University of Maryland, Baltimore County.
There are still tens of millions of Americans without immunity to the virus, and they remain vulnerable to both the short-term and long-term effects of the infection, said Dr. Tom Inglesby, director of the Johns Hopkins Bloomberg School of Public Health’s Center for Public Safety.
Updated
April 27, 2022, 10:22 pm ET
“Betting that you’re in your 60s is a big gamble,” he said. “For anyone who has not been vaccinated and reinforced, I would take this new data as a direct message to do so, or I expect the virus to probably catch up with you if it hasn’t already.
Although the number of cases is increasing again, especially in the north-east, the increase in hospitalizations is minimal and the number of deaths is still decreasing. According to the agency’s latest criteria, more than 98 percent of Americans live in low- or medium-risk communities.
Even among those hospitalized, “we see less oxygen use, less intensive care, and fortunately we haven’t seen an increase in related deaths,” said CDC Director Dr. Rochelle Valensky. . “We hope that the positive trends will continue.”
The country has seen about a five-fold drop in PCR tests for the virus since the peak of Omicron, making it difficult to track new cases. But the number is far smaller, about 70 times lower, said Dr. Valenski, reflecting “a real and reliable decline in our common cases.”
Omicron’s new sub-variants, called BA.2 and BA.2.12.1, replaced the previous iteration, BA.1, which began circulating in the country in late November and sent cases to record highs in a matter of weeks.
“Of course, they are even more infected now, because BA.2 will have infected some who have avoided it so far,” said Dr. Hanaj.
By February, three out of four children and adolescents in the country were already infected with the virus, up from a third of the elderly, according to a new study.
The fact that so many children carry antibodies can offer comfort to parents aged 5 and under who do not qualify for vaccination, as many of them may have acquired at least some immunity through infection.
But Dr. Clark called on parents to immunize eligible children as soon as regulators approve a vaccine for them, regardless of their previous infection. Among children hospitalized with the virus, up to 30 percent may need intensive care, she said.
Although many of these children have other medical conditions, about 70 percent of cases of multisystem inflammatory disease, a rare consequence of Covid-19 infection, occur in otherwise healthy children.
“As a pediatrician and parent, I would absolutely recommend that children be vaccinated, even if they have been infected,” said Dr. Clark.
Some experts said they were concerned about the long-term consequences, even in children with mild symptoms.
“Given the very high rate of infection in children and adults earlier this year, I am concerned about the increase in long-term Covid cases as a result,” said Akiko Iwazaki, an immunologist at Yale University who is studying the condition. .
To measure the percentage of the population infected with the virus, the study relied on the presence of antibodies produced in response to infection.
CDC researchers began assessing human antibody levels in 10 places at the start of the pandemic and have since expanded their efforts to all 50 states, the District of Columbia and Puerto Rico. The researchers used a test sensitive enough to identify previously infected people for at least one to two years after exposure.
The researchers analyzed blood samples collected from September 2021 to February 2022 for antibodies to the virus, and then analyzed data by age, sex and geographical location. The researchers looked for a specific type of antibody produced after infection but not after vaccination.
Between September and December 2021, the prevalence of antibodies in the samples steadily increased by one to two percentage points every four weeks. But it jumped sharply after December, increasing by nearly 25 points by February 2022.
The percentage of antibody samples increased from about 45 percent among children 11 years of age and younger and among adolescents 12 to 17 years of age to about 75 percent in both age groups.
By February 2022, approximately 64% of adults aged 18 to 49, about 50% of those aged 50 to 64 and about 33% of older people were infected, according to the study.
Despite record highs during Omicron’s jump, reported statistics may not have captured all infections, as some people have few or no symptoms, may not have chosen testing, or may have been tested at home.
According to an upcoming CDC study, there may be more than three infections in each reported case, Dr. Clark said.
Noah Wayland contributed to a report from Washington.
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