Daily Archives: February 21, 2021

For much of the past year, life in Western Australia has been coronavirus-free. Friends gathered in pubs; people kissed and hugged their relatives; children went to school without temperature checks or wearing masks. The state maintained this enviable position only by placing heavy restrictions on travel and imposing lockdownssome regions entered a snap lockdown at the beginning of the year after a security guard at a hotel where visitors were quarantined tested positive for the virus. But the experience in Western Australia has provided a glimpse into a life free from the SARS-CoV-2 coronavirus. If other regions, aided by vaccines, aimed for a similar zero-COVID strategy, then could the world hope to rid itself of the virus?

Its a beautiful dream but most scientists think its improbable. In January,Natureasked more than 100 immunologists, infectious-disease researchers and virologists working on the coronavirus whether it could be eradicated. Almost 90% of respondents think that the coronavirus will become endemicmeaning that it will continue to circulate in pockets of the global population for years to come (see 'Endemic future').

Eradicating this virus right now from the world is a lot like trying to plan the construction of a stepping-stone pathway to the Moon. Its unrealistic, says Michael Osterholm, an epidemiologist at the University of Minnesota in Minneapolis.

But failure to eradicate the virus does not mean that death, illness or social isolation will continue on the scales seen so far. The future will depend heavily on the type of immunity people acquire through infection or vaccination and how the virus evolves. Influenza and the four human coronaviruses that cause common colds are also endemic: but a combination of annual vaccines and acquired immunity means that societies tolerate the seasonal deaths and illnesses they bring without requiring lockdowns, masks and social distancing.

More than one-third of the respondents toNatures survey thought that it would be possible to eliminate SARS-CoV-2 from some regions while it continued to circulate in others. In zero-COVID regions there would be a continual risk of disease outbreaks, but they could be quenched quickly by herd immunity if most people had been vaccinated. I guess COVID will be eliminated from some countries, but with a continuing (and maybe seasonal) risk of reintroduction from places where vaccine coverage and public-health measures have not been good enough, says Christopher Dye, an epidemiologist at the University of Oxford, UK.

The virus becoming endemic is likely, but the pattern that it will take is hard to predict, says Angela Rasmussen, a virologist from Georgetown University, who is based in Seattle, Washington. This will determine the societal costs of SARS-CoV-2 for 5, 10 or even 50 years in the future (see Coronavirus: here to stay?).

Five years from now, when childcare centres call parents to tell them that their child has a runny nose and a fever, the COVID-19 pandemic might seem a distant memory. But theres a chance the virus that killed more than 1.5 million people in 2020 alone will be the culprit.

This is one scenario that scientists foresee for SARS-CoV-2. The virus sticks around, but once people develop some immunity to iteither through natural infection or vaccinationthey wont come down with severe symptoms. The virus would become a foe first encountered in early childhood, when it typically causes mild infection or none at all, says Jennie Lavine, an infectious-disease researcher at Emory University in Atlanta, Georgia.

Scientists consider this possible because thats how the four endemic coronaviruses, called OC43, 229E, NL63 and HKU1, behave. At least three of these viruses have probably been circulating in human populations for hundreds of years; two of them are responsible for roughly 15% of respiratory infections. Using data from previous studies, Lavine and her colleagues developed a model that shows how most children first come down with these viruses before the age of 6 and develop immunity to them. That defence wanes pretty quickly so it is not sufficient to block reinfection entirely, but it seems to protect adults from getting sick, says Lavine. Even in children, the first infection is relatively mild.

Whether immunity to SARS-CoV-2 will behave in the same way is so far unclear. A large study of people who have had COVID-19 suggests that their levels of neutralizing antibodieswhich help to block reinfectionstart to decline after around six to eight months. But their bodies also make memory B cells, which can manufacture antibodies if a new infection arises, andT cells that can eliminate virus-infected cells, says Daniela Weiskopf, an immunologist at the La Jolla Institute for Immunology in California, who co-authored the study. Its yet to be established if this immune memory can block viral reinfectionalthough cases of reinfection have been recorded, and new viral variants might make them more likely, they are still considered rare.

Weiskopf and her colleagues are still tracking the immune memory of people infected with COVID-19 to see if it persists. If most people develop life-long immunity to the virus, either through natural infection or vaccination, then the virus is unlikely to become endemic, she says. But immunity might wane after a year or twoand alreadythere are hints that the virus can evolve to escape it. More than half the scientists who responded toNatures survey think waning immunity will be one of the main drivers of the virus becoming endemic.

Because the virus has spread around the world, it might seem that it could already be classed as endemic. But because infections continue to increase worldwide, and with so many people still susceptible, scientists still technically class it as in a pandemic phase. In the endemic phase, the number of infections becomes relatively constant across years, allowing for occasional flare-ups, says Lavine.

To reach this steady state could take a few years or decades, depending on how quickly populations develop immunity, says Lavine. Allowing the virus to spread unchecked would be the fastest way to get to that pointbut that would result in many millions of deaths. That path has some huge costs, she says. The most palatable path is through vaccination.

Countries that have begun distributing COVID-19 vaccines soon expect to see a reduction in severe illness. But it will take longer to see how effectively vaccines can reduce transmission. Data from clinical trials suggest that vaccines that prevent symptomatic infection might also stop a person from passing on the virus.

If vaccines do block transmissionand if they remain effective against newer variants of the virusit might be possible to eliminate the virus in regions where enough people are vaccinated so that they can protect those who are not, contributing to herd immunity. A vaccine that is 90% effective at blocking transmission will need to reach at least 55% of the population to achieve temporary herd immunity as long as some social distancing measuressuch as face masks and many people working from homeremain in place to keep transmission in check, according to a modeldeveloped by Alexandra Hogan at Imperial College London and her colleagues. (A vaccine would need to reach almost 67% of people to provide herd immunity if all social distancing measures were lifted.) But if the rate of transmission increases because of a new variant, or if a vaccine is less effective than 90% at blocking transmission, vaccine coverage will need to be greater to blunt circulation.

Vaccinating even 55% of the population will be challenging in many countries. The virus will stick around if parts of the world dont get vaccinated, says Jeffrey Shaman, an infectious-disease researcher at Columbia University in New York City.

Even if the virus remains endemic in many regions, global travel will probably resume when severe infections are reduced to levels that health services can cope with, and when a high proportion of people who are vulnerable to severe illness have been vaccinated, says Dye.

The 1918 influenza pandemic, which killed more than 50 million people, is the yardstick by which all other pandemics are measured. It was sparked by a type of virus known as influenza A, which originated in birds. Almost all cases of influenza A since then, and all subsequent flu pandemics, have been caused by descendants of the 1918 virus. These descendants circulate the globe, infecting millions of people each year. Flu pandemics occur when populations are naive to a virus; by the time a pandemic virus becomes seasonal, much of the population has some immunity to it. Seasonal flu still has a significant toll globally, claiming roughly 650,000 lives per year.

Jesse Bloom, an evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle, thinks the coronavirus might follow a similar path. I do think SARS-CoV-2 will become a less serious problem and something like flu, he says. Shaman and others say the virus could also settle into a seasonal pattern of annual winter outbreaks similar to flu.

Flu seems to evolve much faster than SARS-CoV-2, allowing it to sneak past the immune systems defences. This feature is why flu vaccines need to be reformulated each year; that might not be needed for SARS-CoV-2.

Still, the coronavirus might be able to dodge immunity acquired by infection, and possibly outsmart vaccines. Already, laboratory studies show that neutralizing antibodies in the blood of people who have had COVID-19 are less capable of recognizing a viral variant first identified in South Africa (called 501Y.V2), than variants that circulated earlier in the pandemic. That is probably because of mutations in the viruss spike protein, which vaccines target. Trial results suggest thatsome vaccines might be less effective against 501Y.V2than against other variants, andsome vaccine makers are exploring redesigns of their products.

Still, the immune system has lots of tricks up its sleeve, and can respond to many features of the virus, not just spike, says Lavine. The virus is probably going to have to go through lots of mutations to make a vaccine ineffective, she says.Preliminary trial resultsalso suggest that vaccinescan protect people with 501Y.V2against severe disease, says Rasmussen.

More than 70% of the researchers surveyed byNaturethink that immune escape will be another driver of the viruss continuing circulation (see 'Driving factors'). This would not be a first for a human coronavirus. In a studyyet to be peer reviewed, Bloom and his colleagues show that the endemic coronavirus 229E has evolved so that neutralizing antibodies in the blood of people infected with the viral variant circulating in the late 1980s and early 1990s are much less effective against more recent variants. People are reinfected with 229E over their lifetime, and Bloom suspects that it might be harder to stave off the variants that have evolved to escape previous immunity. But scientists dont know whether these reinfections are associated with worse symptoms. I would expect that over many years, accumulated mutations to SARS-CoV-2 will more completely erode neutralizing antibody immunity as we saw for CoV-229E, although I cant say for sure how the rates will compare among the two coronaviruses, says Bloom.

Bloom thinks its probable that SARS-CoV-2 vaccines will need to be updated, possibly every year. But even then, immunity from either past vaccination or infection will probably blunt serious disease, he says. And Lavine notes that even if people are reinfected, this might not be a big deal. With the endemic coronaviruses, frequent reinfections seem to boost immunity against related variants and typically people experience only mild symptoms, she says. But it is possible that vaccines wont stop some people developing severe symptoms, in which case the virus will continue to be a significant burden on society, says Shaman.

If SARS-CoV-2 vaccines block infection and transmission for life, the virus might become something akin to measles. Its probably less likely [than other scenarios] but its still possible, says Shaman.

With a highly effective measles vaccinetwo doses and a person is protected for lifethe measles virus has been eliminated in many parts of the world. Before a vaccine was developed in 1963, major epidemics killed about 2.6 million people, mostly children, a year. Unlike flu vaccines, the immunization for measles has never needed to be updated because the virus has yet to evolve in ways that evade the immune system.

Measles is still endemic in parts of the world with insufficient immunization. In 2018, aglobal resurgence killed more than 140,000 people. A similar situation could emerge with SARS-CoV-2 if people decline vaccines. A survey of more than 1,600 US citizens found that more than one-quarter would definitely or probably decline a COVID-19 vaccine, even if it were free and deemed safe (seego.nature.com/3a9b44s). How successful we are at addressing those concerns will determine how many people get the vaccine and how many remain susceptible, says Rasmussen.

The future of SARS-CoV-2 will also depend on whether it establishes itself in a wild animal population. Several diseases brought under control persist because animal reservoirs, such as insects, provide chances for pathogens to spill back into people. These include yellow fever, Ebola and chikungunya virus.

SARS-CoV-2 probably originated in bats, but it might have passed to people through an intermediate host. The virus can readily infect many animals, including cats, rabbits and hamsters. It is particularly infectious in mink, andmass outbreaks on mink farmsin Denmark and the Netherlands have led to huge animal culls. The virus has also passed between minks and people. If it became established in a wild-animal population and could spill back into people, it would be very difficult to control, says Osterholm. There is no disease in the history of humankind that has disappeared from the face of the Earth when zoonotic disease was such an important part of, or played a role in, the transmission, he says.

The path that SARS-CoV-2 might take to become an endemic virus is challenging to predict, but society does have some control over it. In the next year or two, countries can reduce transmission with control measures until enough people have been vaccinated either to achieve herd immunity or to drastically reduce the severity of infections. That would significantly reduce deaths and severe disease, says Osterholm. But if countries abandon strategies to reduce spread and let the virus reign unchecked then the darkest days of the pandemic are still ahead of us, he says.

This article is reproduced with permission and wasfirst publishedon February 16 2021.

Originally posted here:

The Coronavirus is Here to StayHere's What That Means - Scientific American

Like every other virus before it, SARS-CoV-2 has only one goal: to survive.

The longer an outbreak rages, the more people contract but survive the infection, leaving the virus with a dwindling number of vulnerable bodies to infect.

Its best chance of longevity is to evolve.

In doing so, the virus has to strike the right balance. If it becomes too deadly, it risks killing its host before finding another.

So the trick is to become more transmissible, but less deadly, vastly increasing the virus's chances to spread and persist.

We may never know exactly how the UK variant came to be, but it seems likely that about six months into the pandemic, the virus found the perfect body in which to perform this transformation.

From this single infection, a new form of coronavirus emerged, and it's carved a deadly path across the world.

As the end of 2020 approached, UK health advisers became increasingly worried about a second wave gripping the country.

In September, they noticed that the coronavirus was spreading at a faster rate. And with winter on the way, cases were only expected to increase.

As experts discussed the need for more action, the government moved to a higher alert level.

"This country now faces a tipping point in its response and it is vital everybody plays their part now to stop the spread of the virus and protect lives," British Health Secretary Matt Hancock warned at the time.

But already a new variant had emerged. In the space of a few months, it would take over the country.

Referred to by an innocuous string of letters and numbers, VUI-202012/01 or variant B117, it was first identified in the county of Kent on September 20.

Its existence wasn't confirmed by the UK government until December 14. By then, the strain was already spreading with dangerous efficiency, causing a huge spike in cases in south-east England and London.

At the time, UK officials warned it could be 70 per cent more transmissible. Further studies have suggested it could be anywhere from 36 to 71 per cent more infectious than the original Wuhan virus.

Either way, the variant had changed the course of the pandemic in the UK.

And just a month later, its tentacles were stretching around the globe.

It's now in 80 countries, including Australia, and triggered swift lockdowns in Queensland, Victoria and WA.

The exact circumstances of the UK variant's birth may forever remain a mystery.

But most scientists agree it probably evolved in just one person whose infected body was plagued by the virus for a longer time than the average 14-day incubation period.

That patient may have had a long-term, chronic COVID-19 infection, according to University of Queensland virologist Kirsty Short.

"Perhaps [it was] an individual who's immunocompromised," she said.

When influenza infects a person with a chronic medical condition, their immune system takes longer to fight off the virus.

"They can be infected with influenza for months [and are] actually more likely to generate these viral variants than an individual who has a short and acute infection," Dr Short said.

"So, let's imagine that the virus mutates once every time it replicates. If you have an individual in whom the virus has replicated 500 times, there's going to be more mutations than in the individual in whom the virus is replicated five times."

The one silver lining of this pandemic that scientists had identified early on was that coronaviruses mutate far slower than influenza or HIV.

Previous studies have found SARS-CoV-2 usually shows no more than a few mutations, and these can build at a relatively consistent rate over time.

One estimate suggested circulating SARS-CoV-2 lineages accumulate at a rate of about one to two mutations per month.

The UK variant, however, is different.

It has 23 mutations compared with the original virus discovered in Wuhan, 17 of which have appeared since the virus diverged from its most recent version.

Damian Purcell was at his Melbourne lab in late 2020 when he came across a "big surprise" in an online database of global SARS-CoV-2 genome sequences.

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The head of the molecular virology laboratory at The Peter Doherty Institute for Infection and Immunity in Melbourne was looking at the details of the new UK variant.

"We were really surprised, actually, we looked at this and said, 'Wow, look, look how many mutations this virus has got, and look where they are, there's so many in the spike protein'."

A spike protein is found on the outside of the virus and is what fits to the receptors inside our bodies and allows the virus to infect us.

It essentially acts like a key unlocking our body to the coronavirus infection.

"That's the protein that we're most interested in, in terms of understanding the efficacy of vaccines that we're involved in testing," Professor Purcell said.

The UK variant's strange features swiftly earned it a nickname.

"We actually initially called this virus Frankenstein," Professor Purcell said.

"Essentially it was made up of many different parts, it has mutations that we've seen in individual viruses here and there, but they're all popping up in the one virus. So it was a big surprise."

Countries in the grip of soaring infections have a higher chance of producing these variants as the virus seeks out more hosts.

But there is a possibility that the UK strain may have started elsewhere, entering the country through an unsuspecting overseas traveller.

Professor Purcell said the discovery of the strain may have been made possible by the fact the UK studies more genome sequences of positive COVID cases than most other countries.

"So the UK may have seen it because they were looking for it. And if you don't look, you don't find it," he said.

But while they may have had the tools to identify new strains, UK authorities were still playing catch-up as this seemingly fast-spreading variant raged around the country.

By November 2020, around a quarter of cases in London were identified as having the new variant. By mid-December, it had reached 60 per cent.

The UK health system was nearing breaking point and public health experts warned of a deadly winter like no other.

With few options left, Prime Minister Boris Johnson soon delivered the Christmas message no-one wanted to hear.

"It is with a very heavy heart I must tell you we cannot continue with Christmas as planned," Mr Johnson said on December 19.

"I sincerely believe there is no alternative open to me."

The UK strain is not the first time a variant of SARS-CoV-2 has emerged. There could be thousands of different versions of the virus currently circulating the world.

More often than not, a variant doesn't have much impact on an outbreak, and many disappear.

But now and then a virus has a breakthrough. A new strain finds a way to infect more hosts and in rare cases, becomes the dominant force in a pandemic.

While more recently the focus has been on the UK variant, other experts are closely monitoring a potential new strain identified in the US state of California.

But if there's one mutation above all others that scares scientists, it's one called E484K.

"We give many of the virus strains little names, pet names in the lab. There's another one mutation associated with B1.351, which is also known as a South African virus," Professor Purcell said.

"It's got this mutation known as E484K. That's been dubbed 'Eek', because of its potential to escape antibody immunity."

E484K can make it harder for the immune system to recognise and fight the virus, even if the body supposedly learned how to fight the virus from a vaccine.

What worries experts is how this could impact the rollout of COVID-19 vaccines, which may not be as effective against emerging variants.

Earlier this month, South Africa paused its rollout of the AstraZeneca COVID-19 vaccine after a small study suggested it offered minimal protection against mild and moderate infection from its coronavirus strain.

It sent the Oxford team scrambling for a fix. But the reality is these kinds of setbacks are to be expected in vaccine development, especially as more strains surface.

The perfect COVID-19 vaccine may never exist, according to Larisa Labzin from the Institute for Molecular Bioscience at the University of Queensland.

"When I say that, I mean one that would essentially help us eradicate the virus altogether," she said.

"It would stop transmission, it would work against all potential variants, it would mean that we could go back to pre-COVID times immediately."

But the existing vaccines on the market may be able to prevent severe cases of COVID-19 associated with the South African variant.

"I think the evidence is still that the Oxford-AstraZeneca vaccine is going to be able to do that. And we're going to be able to reach more people more quickly with that," Dr Labzin said.

"It can be just a stopgap it'll give us the time to manufacture potentially those other vaccines that are more effective.

"And we'll be able to update the vaccines to reflect the new variants as well."

The emergence of new variants shows us that the threat posed by the coronavirus isn't going away, even with vaccines rolling out in some countries.

Instead, following public health advice wearing masks, maintaining social distancing, hand washing and avoiding mass gatherings remains more important than ever.

"These strains have got a small leg-up. They're not Superman compared to the original," Professor Purcell said.

"They were a little bit more aggressive, more successful, but those measures still work equally well against them."

Still, he believes our safest way out of the crisis still rests on the worldwide rollout of vaccines.

"[It's] going to be crucial in squashing the opportunity for the virus to spit out these freaks, these unlucky mutations that are successful and break vaccine immunity," he said.

"So the more people we can vaccinate and the sooner we can vaccinate, the better."

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UK coronavirus variant spreading rapidly around the world likely emerged from a single infection - ABC News

As coronavirus cases plummet nationwide and vaccinations total 1.7 million Americans a day and rising, health experts are increasingly striking a new tone in their pandemic assessments: optimism.

I could be wrong, but I dont think were going to see a big fourth surge, said Dr. Paul Offit, a vaccine expert at Childrens Hospital of Philadelphia. I think weve 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 replay the nightmare of last year.

The arrival of spring will likely aid the ongoing precipitous drop in coronavirus cases, as warmer weather allows people to spend more time outdoors and creates a less hospitable environment for the virus, experts say.

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

While 12% of Americans have received at least one dose of the COVID-19 vaccine, far more people approximately 35% of the nations population have already been infected with the coronavirus, Offit estimated. Studies have found that people who survive COVID-19 have immunity for several months, though it likely lasts even longer.

UC San Francisco epidemiologist Dr. George Rutherford said one of the reasons why cases are dropping so fast in California is because of naturally acquired immunity, mostly in Southern California. He estimated that 50% of Los Angeles County residents have been infected with the virus at some point.

Were really talking something starting to sound and look like herd immunity although that true herd immunity is a ways off in the future, Rutherford said recently.

Herd immunity is reached when so many people have immunity that a virus cannot find new hosts and stops spreading, resulting in community-wide protection. Scientists believe that in the case of the coronavirus, the threshold could be as high as 90%. The United States has not met this threshold but each step toward it slows transmission, experts say.

The effects may be greatest in places that endured the worst COVID-19 surges, including Los Angeles. After a horrific autumn and winter wave that has killed more than 12,000 people, an estimated 33% to 55% of county residents have already been infected with the coronavirus, according to USC researchers.

Those past infections have blunted transmission of the coronavirus so significantly that they have changed the current trajectory of the outbreak in L.A. County, where new daily cases have been falling for five weeks, said Dr. Roger Lewis, director of COVID-19 hospital demand modeling for the L.A. County Department of Health Services.

If you had the exact same behavior and type of virus circulating that we have right now, but we were at the beginning of the pandemic and no one was immune yet ... wed be in the midst of an ongoing surge, he said. The fact that cases are going down right now, as opposed to going up, is because approximately a third of everybody in Los Angeles County is immune to COVID.

But experts caution that the battle is not yet won.

New coronavirus variants could undermine these projections, either by proving more resistant to existing vaccines or by finding a way to spread more easily. Shifts in behavior could also render this good news moot, as it holds only if people stick to the precautions they have been taking thus far, experts say.

I dont want to provide a false sense of assurance here, said L.A. County chief science officer Dr. Paul Simon, who pointed out that 60% of Angelenos would remain vulnerable even if more than a third have already been infected with the coronavirus. Unless theyve had vaccination, they continue to be susceptible. I think we need to continue to be vigilant.

Nationwide, coronavirus cases have dropped to levels not seen since late October, according to federal officials. In California, approximately 7,000 people are testing positive for the coronavirus each day, compared with 45,000 at the peak of the states winter surge.

In L.A. County, officials currently estimate the R value a measure of how many people a person with the virus goes on to infect to be around 0.8. Anything below 1 means an outbreak is shrinking, and anything above 1 means its growing.

If so many people in the county werent already immune, the R value would be about a third higher, or just above 1, Lewis said. Even that slight increase has major consequences for a virus prone to spreading exponentially.

The fact that the virus only has two-thirds as many people to jump to as it did early on slows it down, Lewis said.

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

The large number of infections has come at a high cost. The nations death toll is approaching 500,000, far greater than any country in the world, and even more have survived but continue to suffer lingering effects of their illnesses, some of them severe. Allowing COVID-19 to run rampant to quickly achieve herd immunity, as some had promoted early in the pandemic, would have led to even more deaths and chronic health problems, experts say.

It remains unclear exactly what the threshold for herd immunity is with this virus with some scientists estimating that herd immunity may be achieved when 50% of people are immune, while others believe the threshold is closer to 90%, said L.A. Countys Simon. The uneven geographical distribution of infections may also leave some pockets of the county more vulnerable than others, he said.

We dont know quite yet what level of vaccination and protection would be required to get herd immunity across the county, Simon said in briefing Friday. As we see the number of new cases drop dramatically that will be I think the best clue that were reaching herd immunity, particularly if we see it across the county.

The biggest obstacle to ending the pandemic is the proliferation of coronavirus variants, especially if they are more transmissible or less susceptible to vaccines. For instance, the B.1.1.7 variant that emerged in the United Kingdom is about 50% more contagious than its predecessors and could fuel outbreaks in places where large swaths of people remain vulnerable to disease.

Dr. Peter Hotez, dean of Baylor College of Medicines National School of Tropical Medicine, said he thinks that flying to visit friends and family will be normal and safe by August. But because of the variants he cautioned people to beware the Ides of March.

Thats, I think, the biggest crisis facing us right now in our COVID-19 pandemic, he said in a recent interview with the American Medical Assn. As bad as 2020 was, now were looking at version 2.0 of this pandemic from the variants.

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

That line hasnt been crossed, he said. You just want to keep people out of the hospital and it looks like to date theres not a variant that has escaped either disease- or vaccine-induced immunity.

At a UCSF Department of Medicine COVID seminar last week, Dr. Monica Gandhi, an infectious disease specialist, put it simply: Try not to worry about the variants.

Offit said he remains hopeful about the nations trajectory through the summer and as more people get vaccinated. What worries me a little bit is when you hit September, and then it gets colder again, and there may be a variant that emerges, and people stop wearing masks and physically distancing, Offit said.

Dr. Rochelle Walensky, director of the U.S. Centers for Disease Control and Prevention, cautioned against viewing the downward case trends as a reason to let up on masking and other safety precautions.

In an interview with the Journal of the American Medical Assn., Walensky said she hoped for the best, but also warned of a worst-case scenario that people will stop wearing masks and physically distancing too early and that many will prematurely declare theyve had enough of the pandemic and wont get vaccinated.

How this goes is going to depend on 330 million individuals, Walensky said. Because while I really am hopeful for what could happen in March and April, I really do know this could go bad so fast. And we saw it in November. We saw it in December. We saw what can happen.

Dr. Annabelle de St. Maurice, a pediatric infectious disease specialist at UCLA, said she sympathizes with officials trying to walk a fine line between keeping morale up and not making people feel so optimistic that they led their guard down.

In L.A. in particular, the numbers have improved drastically, she said, but they remain almost as high as they were during the deadly summer surge.

It is reason to celebrate, and you want people to celebrate it, but you want them to do that physically distanced while wearing a mask, she said.

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COVID-19 surge is now helping to create herd immunity - Los Angeles Times

SIOUX FALLS, S.D. (KELO) Active cases of coronavirus dipped below 2,000 for the first time since August 26, 2020 as 147 new cases were reported in Saturdays update from the South Dakota Department of Health.

Active cases are now at 1,997, down from Friday (2,028).

According to the latest update, 147 new total coronavirus cases were announced bringing the states total case count to 111,165, up from Friday (111,018).

Total recovered cases are now at 107,309, from Friday (107,137).

The South Dakota Department of Health reported six new deaths due to COVID-19 in Saturdays update. The death toll is now at 1,859. The new deaths listed include three men and three women in the following age ranges: 30-39 (1), 40-49 (1), 60-69 (1), 70-79 (1), 80+ (2).

Current hospitalizations are at 95, up from Friday (91). Total hospitalizations are at 6,509.

Total persons negative is now at 306,170, up from Friday (305,524).

There were 793 new persons tested reported on Saturday. Saturdays new person-tested positivity rate is 18.3%.

The latest seven-day all test positivity rate reported by the DOH is 7.6%. The DOH calculates that based on the results of the PCR test results but doesnt release total numbers for how many PCR tests are done daily. The latest one-day PCR test positivity rate is 4.9%.

As of Saturday, 85,042 doses of the Pfizer vaccine and 95,254 doses of the Moderna vaccine have been administered to 119,896 total persons.

According to the South Dakota Department of Health, 31,781 people have received the second dose of the Moderna vaccine, 28,619 people have completed the Pfizer vaccine series.

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COVID-19 in South Dakota: 147 total new cases; Death toll rises to 1,859; Active cases at 1,997 - KELOLAND.com

LONDON (Reuters) - All adults in Britain will be offered a first shot of a COVID-19 vaccine by the end of July, Prime Minister Boris Johnson said on Saturday ahead of a planned announcement on the cautious reopening of the economy from lockdown.

FILE PHOTO: A woman receives an Oxford-AstraZeneca coronavirus disease (COVID-19) vaccine at a COVID-19 vaccination centre at Cwmbran Stadium in Cwmbran, South Wales, Britain February 17, 2021. Geoff Caddick/Pool via REUTERS/File Photo

Johnson will set out a roadmap to ease Englands third national lockdown on Monday, having met a target to vaccinate 15 million Britons from higher-risk categories by mid-February.

Britain now aims to give a first dose to all over-50s by April 15, the government said, having previously indicated it wished them to receive the shot by May.

If all adults receive a dose by the end of July, it will be well ahead of a previous target that they would receive a vaccine by autumn.

After suffering the worlds fifth-worst official COVID-19 death toll and a series of mishaps in its pandemic response, Johnsons government moved faster than much of the West to secure vaccine supplies, giving it a head start.

Johnson cautioned that there was a need to avoid complacency, adding that lockdown would only be lifted slowly.

We will now aim to offer a jab to every adult by the end of July, helping us the most vulnerable sooner, and take further steps to ease some of the restrictions in place, Johnson said in a statement.

But there should be no doubt - the route out of lockdown will be cautious and phased, as we all continue to protect ourselves and those around us.

So far, he United Kingdom has given a first dose of vaccine to 17.2 million people, over a quarter of its 67 million population and behind only Israel and the United Arab Emirates in vaccines per head of population.

Two vaccines - one made by Pfizer and BioNTech, and another developed by the University of Oxford and AstraZeneca - are being rolled out, and UK officials have advised that there can be a 12 week gap between doses.

Reporting by Alistair Smout; Editing by Ros Russell

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Britain to offer all adults a COVID-19 vaccine by end of July - Reuters