专家：德尔塔变异可能是冠病最后一个变种

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专家：德尔塔变异可能是冠病最后一个变种

文 / 林煇智

10/07/2021

美国国家科学院院士库宁称，德尔塔在很短的一段时间内成为主要流行的毒株，无疑是一个稳定的毒株。（彭博社）

（早报讯）有专家认为，目前全球主要流行的德尔塔毒株是冠病病毒疫情发展的高峰，很可能成为该病毒的最后一个变种。

中通社报道，美国国家科学院院士库宁（Eugene Koonin）在出席新西伯利亚科尔佐沃科学城举行的生物技术论坛OpenBio时称，德尔塔在很短的一段时间内成为主要流行的毒株，无疑是一个稳定的毒株。

至于这种毒株是否会被另一种毒株取代，或是最后一种毒株，库宁解释说，在众多人群接种疫苗的情况下，病毒很难突破已形成的免疫防御——在保持很高的能力与受体产生联系的同时“逃避”抗体。他指出：“这种德尔塔产生能逃避抗体突变的机会不是很大。”

库宁坦言，他不确定病毒是否会发展到一个新的水平，但上述因素表明，情况幷没有那么糟糕。

当前，冠病病毒变种毒株德尔塔仍在全球肆虐。世卫组织周二（5日）发布的每周流行病学报告显示，目前已有192个国家和地区出现德尔塔变异株感染者。

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Could delta be the variant to end the pandemic? Experts say maybe

BY ERIN BILLUPS

10/07/2021

*Courtesy: The Centers for Disease Control and Prevention*

A return to normal — meaning life without social distancing and masks — seemed within reach at the end of spring.

When Spectrum News spoke with Dr. Monica Gandhi in early June, the infectious disease physician was urging schools to consider allowing children to return in the fall sans masks, saying all that was needed was for the adults around them to be vaccinated.

Then came the highly contagious delta variant, and the realization that many adults weren’t getting inoculated.

Now, Dr. Gandhi, a professor at the University of California, San Francisco School of Medicine, says before we’ll see “normal” again, kids will need to be vaccinated too, and must continue masking until that happens.

“Unfortunately, delta, I think, really changed the equation for children and for the country, and it’s just so much more highly transmissible that we didn’t have the levels of immunity in our population to keep others safe. Meaning we need higher and higher levels,” Dr. Gandhi said.

What You Need To Know

Experts say they do not anticipate another devastating wave like we saw with the highly contagious delta variant
The immunity induced by a COVID infection offers strong protection to some, and may help us reach herd immunity
Experts say that it is still important to get vaccinated, even if you had the virus
COVID will likely never disappear, but will become more manageable

But Dr. Gandhi says a return to normal is now finally in sight, in part because the FDA may soon authorize a COVID-19 vaccine for younger children – and because the delta variant is essentially forcing higher levels of immunity throughout the population.

Although ‘normal’ is nearly here, she says, it is at a much higher cost than anyone wanted to pay.

“I think delta will be the variant to end them all.”

“The most painful way to get immunity is natural infection, the painful and unfortunately sometimes deadly way. But [even] if we don’t get our vaccination rates up, I think by the end of this year we will have enough immunity in our population, either through vaccination and natural infection,” Dr. Gandhi said. “I think delta will be the variant to end them all.”

Particularly because history shows that disruptive viruses eventually peter out. “Usually, if you develop too many mutations, the virus actually becomes weaker as opposed to stronger. It’s sort of evolutionary biology,” Dr. Gandhi added.

Again, these are predictions, if we’ve learned anything from the coronavirus pandemic – it’s that anything can happen.

Has the U.S. reached ‘herd immunity’?

Herd immunity is when a sufficient amount of the population is immune or protected against a disease. After a 20-month roller coaster of surging and ebbing coronavirus transmission, and more than 65 percent of those 12 and older fully vaccinated, many are asking the question, aren’t we there yet?

While Gandhi and other experts we spoke to say the country is nearly there, the nation’s leaders tasked with guiding the country out of the pandemic won’t answer the question.

“You know when you are at herd immunity when the virus doesn’t have an opportunity to go from person to person. But right now, we don’t know what that number is,” Dr. Anthony Fauci, the nation’s top infectious disease expert, said during a White House COVID-19 Response Team briefing last week.

“And when you don’t know what the number is, what do you do? You vaccinate as many people as you possibly can, as quickly and as expeditiously as you possibly can. That’s what we should be concentrating on, not any particular number,” Dr. Fauci added.

Vaccines have proven very effective in offering protection. Even among those who were infected after vaccination, referred to as so-called “breakthrough” cases, the vast majority are protected against serious illness and death. But some research is showing that the protection offered through natural immunity shouldn’t be disregarded.

A study of workforce screenings that took place before the delta variant took hold, released coronavirus testing company Curative, found that those who recovered from natural SARS-CoV-2 infections produced decent protection against reinfection.

Researchers say there was no significant difference in the incidence of infection between those who were previously infected and people who were vaccinated.

In fact, there were zero reinfections among the 254 patients who had prior infections, compared with four “breakthrough” cases in the vaccinated group of 739 patients. Researchers concluded that their findings “should provide increased confidence that those previously infected are at very low risk for repeat infections.”

Those previously infected should still get vaccinated

Yale Medicine Immunologist Akiko Iwasaki says natural immunity to coronavirus must be included in the overall picture of whether a population is protected. To get past delta specifically, Iwasaki agrees, a very high level of immunity is needed. “With the delta, you need like 90% of the people immune to establish herd immunity.”

But a recent study she led – soon to be published in a peer reviewed journal – makes the case for vaccinating even if you’ve been previously infected. The Yale researchers found that those with prior infections who were vaccinated, had the greatest protection against coronavirus and its variants.

“Naturally acquired immunity is pretty good at preventing infection and disease,” Iwasaki said. “But there is a huge variation between people as to how much immunity they generate with an infection. So with very mild disease, we have very little antibodies and very little T-cell immunity, whereas people who had more severe disease, they do generate more antibodies and T-cells.”

The caveat, though, is that the immune response triggered is different in each person.

“Because of this variability, we just want to make sure everybody gets protected and a vaccine can do that,” Iwasaki said. “Even if you may have very good immunity already with the master infection, that can also wane over time.”

“Secondly, the vaccines work. As our research has shown, the vaccine will elevate that level even further,” Iwasaki added. “So why not be protected even further if you have that opportunity?”

From pandemic to endemic

New York University Population Health Epidemiologist Anna Bershteyn, who has been modeling out the pandemic for New York City., says with natural infection and vaccinations the city is now at about 83% immunity.

The goal to get past delta and back to normal, she says, is anywhere between 85 and 90 percent.

“When we get close to herd immunity, we’re going to be able to peel some of those layers off. And we have to make smart decisions about which of those layers are the first that get to be peeled off. The faster we make progress with vaccination, the sooner we can get there,” Bershteyn said.

Dr. Gandhi says her home state of California has reached a necessary level of population immunity, with about 90 percent having some level of protection.

The infectious disease expert says coronavirus is here to stay despite efforts to eradicate it. Gandhi says it is time now to follow the lead of other countries that have largely put the pandemic behind them, viewing the virus instead as endemic, or regularly found in circulation.

“Living with an infectious disease is very manageable if we can get it to what we call control,” Gandhi said. “That is another word for a low level. It becomes endemic, but control means that it doesn’t disrupt our lives. We always will have to be vigilant, we keep on vaccinating and we keep on testing and we keep on treating people if we need to.”

It’s time, she says, for the nation’s leaders to offer the public hope – that the pandemic is nearing its end.

“What’s the end game?” she asked. “We haven’t had that messaging here.”

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