The spread of COVID-19 is now helping to build herd immunity

The spread of COVID-19 is now helping to build herd immunity

With coronavirus cases nationwide declining and vaccinations totaling 1.7 million Americans daily and increasing, health experts are increasingly striking a new tone in their epidemiological assessments: optimism.

“I might be wrong, but I don’t think we’re going to see a fourth big boom,” said Dr. Paul Offitt, a vaccine expert at Children’s Hospital of Philadelphia. “I think we’ve seen the worst of it.”

Many epidemiologists and other scientists, while still cautious, say they feel increasingly hopeful that the rest of 2021 will not bring back last year’s nightmare.

The arrival of spring will likely help The sharp decline in the number of cases of coronavirus infection continuesBecause warmer weather allows people to spend more time outdoors and creates a less favorable environment for the virus, experts say.

But the biggest factor, paradoxically, is something the nation has spent the past year trying to prevent.

While 12% of Americans have received at least one dose of the COVID-19 vaccine, far more people – about 35% of the country’s population – have already contracted the coronavirus, according to Offit estimates. Studies have found that people who survive Covid-19 disease have immunity for several months, although it will likely last longer.

Dr. George Rutherford, an epidemiologist at the University of California, San Francisco, said that one of the reasons for the rapid decline in cases in California “is due to the naturally acquired immunity, mostly in Southern California.” It has been estimated that 50% of residents of Los Angeles County have contracted the virus at some point.

Rutherford recently said, “We’re really talking about something that’s starting to look like herd immunity – although this true herd immunity will be far into the future.”

Herd immunity is reached when so many people have immunity such that the virus is unable to find new hosts and stops spreading, thus protecting the entire community. Scientists believe that in the case of the Coronavirus, the threshold could reach 90%. Experts say that the United States has not met this threshold, but that every step towards it slows the transmission of infection.

The effects could be greater in places that endured the worst increases in COVID-19, including Los Angeles. After the horrific autumn and winter wave that killed more than 12,000 people, an estimated 33% to 55% of the county’s population has already contracted the coronavirus, according to University of Southern California researchers.

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Roger Lewis, director of the COVID-19 Hospital Application Form, said these previous infections had hampered transmission of the coronavirus so drastically that they altered the current course of the outbreak in Los Angeles County, where new daily cases decreased for five weeks. For the Los Angeles County Department of Health Services.

“If you had the same behavior and the type of circulating virus that we have now, but we were at the beginning of the epidemic and nobody was immune yet … we would be in the midst of a constant increase,” he said. “The fact that cases are declining at the moment, rather than rising, is because nearly a third of everyone in Los Angeles County is immune to COVID.”

But experts warn that the battle is not yet won.

New coronavirus variants could undermine these expectations, either through Demonstrate greater resistance to existing vaccines Or by finding a way to post more easily. Experts say shifts in behavior could make this good news moot, as it only applies if people stick to the precautions they have taken so far.

“I don’t want to present a false sense of reassurance here,” said Los Angeles County Chief Science Officer Dr. Paul Simon, who indicated that 60% of Angelenos would still be at risk even if more than a third of them were already infected with the virus. Corona Virus. “Unless they are vaccinated, they remain vulnerable to infection. I think we need to continue to be vigilant.”

Nationwide, coronavirus cases have fallen to levels not seen since late October, according to federal officials. In California, nearly 7,000 people tested positive for coronavirus daily, compared to 45,000 at the height of the state’s winter wave.

In Los Angeles County, officials currently estimate the R-value – a measure of the number of people who contract the virus – at around 0.8. Anything less than 1 means the outbreak is shrinking, and anything higher than 1 means it’s growing.

If a lot of people in the county were not already immune, Lewis said, the R value would be about a third higher, or just over 1. Even this slight increase has severe consequences for a virus that is susceptible to exponentially spread.

“The fact that the virus has two-thirds of the number of people who can jump into it only as it did early on slows it down,” Lewis said.

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Since the start of the pandemic, nearly 30 million Americans have tested positive for the coronavirus, but the true number of people who have contracted the virus is likely three or four times higher due to low test levels and the fact that many infected people never show symptoms. Experts say.

The high number of casualties has come at a high cost. The country’s death toll is approaching 500,000, which is far more than any country in the world, and many more have survived but continue to suffer from the lingering effects of their illnesses, some of which are severe. Experts say allowing COVID-19 to spread rapidly to achieve herd immunity, as some promoted early in the pandemic, would have resulted in more deaths and chronic health problems.

Simon from Los Angeles County said it remains unclear exactly what the threshold for herd immunity with this virus is, as some scientists estimate that herd immunity can be achieved when 50% of people are immune, while others believe the threshold is closer to 90%. He said that the uneven geographical distribution of the infection may make some pockets of the province more vulnerable than others.

Simon said in a press release on Friday: “We do not know yet exactly what level of vaccination and protection are required to obtain herd immunity throughout the province.” “Since we’re seeing the number of new cases dropping dramatically – I think that’s the best evidence that we’ve reached herd immunity, especially if we’re seeing it across the county.”

The biggest obstacle to ending the epidemic is the spread of coronavirus variants,
Especially if it is more transmissible or less susceptible to vaccines. For example, the B.1.1.7 variant that appeared in the United Kingdom is 50% more contagious than its predecessors and can lead to outbreaks in places where large sections of people remain vulnerable to disease.

Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, said he believes traveling to visit friends and family will be normal and safe by August. But due to the variables, people have been warned to “be wary of March’s thoughts”.

“I think this is the biggest crisis facing us right now in the COVID-19 pandemic,” he said in a recent interview. Interview with American Medical Assn. “As bad as 2020 was, we are now looking at version 2.0 of this pandemic of variants.”

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Others are more optimistic. Offit said he would be concerned if people who had already contracted COVID-19 or who had been vaccinated were being hospitalized due to infection caused by a new variant.

He said, “This line has not been crossed.” “You just want to keep people out of the hospital and it seems that up to now no variant has survived the immunity resulting from the disease or the vaccine.”

At a symposium on COVID for the Department of Medicine at the University of California, San Francisco, last week, Dr. Monica Gandhi, an infectious disease specialist, said it simply: “Try not to worry about the variables.”

Offit said he still hoped the nation’s path through the summer and as more people were vaccinated. Offit said, “What worries me a little bit is when you get to September, then it gets colder again, and there might be a variable appearing,” and people stop wearing masks and physical distancing.

Dr Rochelle Wallinski, director of the U.S. Centers for Disease Control and Prevention, cautioned against looking at downward-state trends as a reason to ditch the mask and other safety precautions.

In an interview with the Journal of the American Medical Assn. , Walinsky said she was hoping for the best, but also warned of the worst-case scenario – that people stop wearing masks and physical distancing too early and that many will announce prematurely that they have had enough of the pandemic and will not be vaccinated.

“How it will work will depend on 330 million people,” Wallinski said. “Because while I’m really optimistic about what could happen in March and April, I really know that could get worse – very quickly. And we saw that in November. We saw that in December. We saw what could happen.”

Dr. Annabelle de Saint-Maurice, a pediatric infectious disease specialist at the University of California, said she sympathized with officials trying to walk a fine line between preserving morale and not making people so optimistic that they drove their caution.

In Los Angeles especially, the numbers improved dramatically, she said, but remained nearly as high as they were during the fatal summer wave.

She said, “This is a cause for celebration, and you want people to celebrate, but you want them to do it away physically with a mask.”

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