Category Archives: Genetic Medicine

MedicalResearch.com Interview with:David Gurwitz, PhDAssociate ProfessorDepartment of Human Molecular Genetics and BiochemistrySackler Faculty of MedicineTel-Aviv University, Tel-Aviv Israel

MedicalResearch.com: What is the background for this study?

Response: We closely followed the news on COVID-19 epidemiology since it was declared a pandemic, and were puzzled by the low fatality rates reported in nearly all East Asian countries, even that clearly this was in part due to fast response; for example, Taiwan remains the best example for combatting the pandemic.

My past research on serpins (serine protease inhibitors) made me wonder if ethnic differences in some of them are in part related to the relatively low COVID-19 morbidities and fatalities, as serine proteases, in particular TMPPRSS2, are strongly implicated in the SARS-CoV-2 respiratory track cell entry and infection.

Additionally, serine proteases such as neutrophil elastase are highly implicated in inflammatory tissue damage. Guy Shapira, a graduate student of my colleague Professor Noam Shomron, examined mutation records in different ethnic groups for the entire human serpin gene family. He came up with the findings we report regarding a close correlation between national records of the frequencies of the two mutations PiZ and PiS, underlying alpha-1 antitrypsin deficiency, in 67 countries on the global scale, and the current COVID-19 fatalities in the same 67 countries.

MedicalResearch.com: What should readers take away from your report?

Response: Our message is clearly summarized in our closing statements. We urge the biomedical community to study our hypothesis so that it can be validated or refuted. If validated, it has far-reaching consequences for protecting individuals likely to have severe COVID-19 outcomes, including fatal outcomes.

MedicalResearch.com: What recommendations do you have for future research as a result of this work?

Response: If validated by clinical studies, as we state in our article, population-wide screening efforts should be considered for identifying individuals who are carriers of the PiZ or PiS mutations (the most common mutations causing alpha-1 antitrypsin deficiency).

Next, such individuals should be advised to observe strict social distancing, until a vaccine is approved. Once a vaccine becomes available, they should be among those prioritized to be offered a vaccine, while explaining to them that they might be at higher risk than the general population in their country.

We are aware that some people will object a vaccine due to fears of side effects, or fears of conspiracy theories circulated on social media. Therefore, the risk should be assessed, and if found true, should be explained with the highest possible transparency by national healthcare providers

MedicalResearch.com: Is there anything else you would like to add?

Response: We do not have any conflict of interest. We are driven by the wish to reduce the high health and economic burden of COVID-19.

We are also concerned that even once a COVID-19 vaccine is approved, the global supply will not be able to meet the global demand, and in low income countries, and poor people in any country without national health insurance, may be left behind.

Citation:

Shapira, G,Shomron, N,Gurwitz, D.Ethnic differences in alpha1 antitrypsin deficiency allele frequencies may partially explain national differences in COVID19 fatality rates.The FASEB Journal.2020;00:16.https://doi.org/10.1096/fj.202002097

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COVID-19: Genetics Helps Explain National Differences in Infection Rate, Severity and Mortality - MedicalResearch.com

As the global race to produce a vaccine against COVID-19 continues to heat up, researchers from the Peter Doherty Institute for Infection and Immunity and the Monash Institute for Pharmaceutical Sciences have developed two vaccine candidates that are providing encouraging results in preclinical testing.

The results have attracted almost $3 million in funding from the Commonwealth governments Medical Research Future Fund (MRFF).

The approach focuses on the golf tee-shaped protein spikes that dot the surface of the SARS-Cov-2 virus.

The tip of the spike protein is known as the receptor binding domain (RBD), and is considered the most important target for antibodies produced by our immune systems, because this is the part of the virus that attaches to human cells.

In effect, if you can block the attachment, you block the infection.

One of the vaccines isolates the molecular form of the RBD to focus the immune response on this critical region. The other includes messenger RNA (mRNA) to represent the genetic sequence of the virus, effectively tricking the immune system into thinking a virus is present so that it will make the antibodies.

Here, Monash Universitys Professor Colin Pouton, who's working on the vaccine research projects, takes us behind the scenes ofthe process, and explains the importance of collaboration.

Were delivering messenger RNA (mRNA) in common with some of the leading commercial programs. The mRNA contains the genetic code that allows our own cells to make part of the coronavirus spike protein. When our cells make the protein, our immune cells can recognise the protein as foreign, and this leads to production of antibodies.

The goal is to produce antibodies that bind to the virus and prevent infection. This is a new technology for vaccine development, but has a number of important advantages. mRNA can be produced quickly and, if the virus mutates, modified sequences can be produced rapidly. A cocktail of mRNA molecules could be used to hit several strains.

We started working with virologists at the Doherty to analyse the quality of the immune response after vaccination of mice. The Doherty scientists can work with live virus, and can test whether our mouse antisera prevent infection using a cell culture infection model.

The Monash Institute of Pharmaceutical Sciences[MIPS]group includes specialists in mRNA production and formulation, but we dont have specialised handling facilities to study viral infection and the immune responses to vaccines.

Later, we realised that the two groups shared an interest in producing vaccines focused on vaccinating with the receptor binding domain [RBD]. This is a small part of the spike protein, but neutralising antibodies need to bind to the RBD. So were now collaborating by investigating a protein developed by the Doherty group, as well as the mRNA developed by the MIPS group.

The two vaccines RBD protein from the Doherty, and mRNA encoding RBD from MIPS offer an unusual opportunity to compare the attributes of the two delivery approaches head-to-head. We expect theyll result in different responses.

Knowledge of how the vaccines differ will be valuable when designing the response to future emerging viruses.

Collaborations work best when the individual parties bring different and complementary skills that make the case for collaboration compelling. The collaboration with the Doherty group is a good example. Competition between the institutions is not an option, because neither has all the required attributes.

In addition, I think the urgent need to respond to the COVID-19 pandemic has increased the willingness to collaborate.

The laboratory researchers have been able to work throughout the pandemic, but have been restricted by social distancing, reduced occupancy of the labs, and the need to wear masks all day. But the motivation is high, and the huge interest in vaccine development has been inspiring.

Read more:From Baghdad to Melbourne: Dr Harry Al-Wassiti's remarkable journey

The MIPS team is small. Harry Al-Wassiti has done much of the work, assisted by Estelle Suys and two PhD students, Asuka Takanashi and Tom Payne.

Certainly the proof that the mRNA vaccines we designed produced neutralising antibodies in mice was a key moment.

Virologists in Melbourne have been sequencing large numbers of viral isolates greater than 5000 samples. There are lots of mutations as would be expected for a RNA virus but many of the mutations havent changed the threat of the virus.

Some mutations are significant. Theres been at least one mutation circulating in Victoria that binds more strongly to the known receptor (ACE2). This suggests that the vaccine design might need to adapt to mutations, and may need to be given in a seasonal manner. mRNA is particularly adaptable in this respect.

The leading commercial programs will complete their phase three trials within two to three months. If theyre safe and effective, the vaccines could be in use early in 2021.

The availability of vaccines in Australia will depend on the international capacity to produce doses, and whether they can be produced in Australia under licence. The Australian vaccines, if successful, will follow later and the ability to take them forward into efficacy studies will depend on commercial partners and funding.

I arrived in Melbourne in 2001, and Ive always found the environment to be highly collaborative. Proximity of the various universities and institutes in a large city is part of the reason. Also, theres a lot of shared equipment, which fosters collaboration.

The novel coronavirus is very closely related to other coronaviruses, and in particular to the SARS virus. Considering how close they are, there are surprising differences in how contagious each virus is, and how severe the disease caused.

It seems that severe coronavirus infections will be a continuing problem in the future. The pandemic has inspired a huge amount of research just take a look at the BioRxiv platform for disseminating manuscripts prior to peer review. The number of relevant papers that have been published in six months is overwhelming 8762 up to 17 September.

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COVID-19 vaccines, spike proteins, and blocking the deadly virus - Monash Lens

Supreme Court justice Ruth Bader Ginsburg has died at age 87. Ginsburg is most noted for her lifelong fight for equality for women. USA TODAY

Supreme Court Associate Justice Ruth Bader Ginsburg, who died Friday evening,had overcome four bouts with pancreatic, lung and colon cancer dating back two decades.

Ginsburg, 87,could not beat the most recent spread to her liver and died from complications of metastatic pancreatic cancer.

In January, she announcedshe was cancer-free, sayinga periodic scan and biopsy revealed lesions on her liver but that chemotherapy treatment that began in May was "yielding positive results." But by July,Ginsburg said she wasbattling cancer againand was undergoing chemotherapy after a lesion was found on her liver.

"It's fairly uncommon to have so many cancers successfully treated and then to be able to live through them, certainly as long as she did and to tolerate the treatment of these in her 80s, it's a testament to her," said Dr.Kiran Turaga, director of theSurgical Gastrointestinal Cancer Program at the University of Chicago Medicine.

Ginsburg had her first bout of cancer in 1999, when doctors discovered colon cancer at an early stage by accident due to an unrelated abdominal infection. A decade later, when Ginsburg was undergoing regular screenings, doctors discovered pancreatic cancer and removed parts of herpancreas, along with her spleen. In 2018, shehad two cancerous growths removed from her lungs again discovered by chance after she fell and broke several ribs. And last year, Ginsburgwas treatedfor a malignant tumor on her pancreas.

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Ginsburg had yet to graduate high school when her mother,Celia Bader, died from cervical cancer. Years later, her husband, Martin Ginsburg, was diagnosed with testicular cancer and underwent two surgeries. He died in 2010 of complications from metastatic cancer. The two had been married 56 years.

"Like too many Americans, Justice Ginsburg had an extensive history with cancer having lost her mother and husband to the disease," Gary M. Reedy, CEO of the American Cancer Society, said in a statement Friday. "Her personal health history and active survivorship made her an inspiration for many patients and survivors and helped inform her deep commitment to public health policy."

Compared to colon cancer, pancreatic cancer is less common but more deadly. About 57,000 people will be diagnosed with pancreatic cancer this year, and about 47,000 people will die from it, according to the American Cancer Society. While pancreatic cancer accounts for about 3% of all cancers in the U.S., it accounts for about 7% of all cancer deaths.

"It has remained one of the most, if not the most difficult cancer for us to treat," said Dr. Brian Wolpin, director of the Gastrointestinal Cancer Center and Hale Family Center for Pancreatic Cancer Research at Dana-Farber Cancer Institute. "It does tend to present late, and there are not many specific symptoms for pancreatic cancer. They tend to be things like abdominal discomfort or weight loss."

The cancer also tends to be more aggressive,Wolpin said. It grows faster than other types of cancer and is less responsive to treatment.Less than 10% of patientssurvive five years or more after diagnosis, Wolpin said.

"She lived 10 years with this disease. She beat the odds, and it was a remarkable fight," saidDr. Timothy Donahue, chief of surgical oncology at UCLAs Jonsson Comprehensive Cancer Center. "But its not uncommon for this disease to have a long latency period and then come back are recur even more than 10 years later, so we continue to surveil these patients years after their diagnosis."

Pancreatic cancer can be painful because the pancreas is located near many nerve endings, Donahue said. It often causes back pain, he said.

"Not only is it painful, its very difficult to live with because of the weight loss and the extremely poor energy levels," Donahuesaid. "Theres something particular about this tumor that causes many issues for these patients much more so than other comparable cancers."

There are two compartments of the pancreas, andtwo larger categories of pancreatic cancer, Donahue said. Steve Jobs, for example, died from complications of a rare form of pancreatic cancer that is less aggressive.

There's no colonoscopy or mammogram equivalent for pancreatic cancer, and it's often discovered incidentally, experts say.

"We don't have a good detection. You can have a tiny little cancer, and you can operate on it, but it still has a high risk of coming back,"said Dr. Mary Mulcahy, oncologist at Lurie Cancer Center at Northwestern Memorial Hospital.

But researchers are looking into how blood-based tests may be used to screen for pancreatic cancer.

"These are still reasonably early days. Theres no standard blood test that we use yet," Wolpin said. "How we would then apply that in a large population would be hard to figure out."

Others are investigating the role of a specific cancer-causing genetic mutation, known as KRAS, which is implicated in nearly all pancreatic cancer cases, according to Donahue. There's a campaign underway to encourage all patients newly diagnosed with pancreatic cancer to get their genes sequenced so researchers can learn more about the genetics of the disease, Donahue said.

"Universal genetic testing is important not only because it might influence some of the treatments they receive for their own cancer, but also whether their immediate family members need to speak with a genetic counselor about receiving a genetic test themselves," saidAnirban Maitra, a pancreatic cancer researcher at MD Anderson Cancer Center.

'RGB': How 'Notorious' Ruth Bader Ginsburg became a pop-culture icon

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While pancreatic cancer typically effects people who are older, colon canceris increasingly affecting young Americans.Deaths from colon and rectal cancers have been declining for several decades due to improved screening and treatment measures, but deaths among young people have been increasing slightly in recent years, according to researchers.

Late last month, actor Chadwick Bosemandied from colon cancerat just 43.

But science is making huge strides. In the U.S., the five-year survival rate for all cancers combined has increased substantially since the early 1960s, from 39% to 70% among white people and from 27% to 64% among Black people, according to the American Cancer Society.

"Even today, people think cancer is a death diagnosis," Turaga said. "But in the last three years, there are so many new years of treating cancers. We're making so much progress."

Contributing: Richard Wolf, Ken Alltucker, Kristine Phillips

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Ginsburg v. cancer was a 'remarkable fight': RBG battled five bouts of cancer over two decades - USA TODAY

This study, published last Thursday in the Journal of Medical Internet Research, found a statistically significant uptick in clinic and hospital visits by patients who reported respiratory illnesses as early as the week of December 22.

The researchers noticed this trend by looking through nearly 10 million medical records from the UCLA Health system, including three hospitals and 180 clinics.

Elmore and her colleagues noticed the spike in respiratory cases by searching the field in medical records that lists why someone came to the clinic and searched for the symptom "cough." They looked at the records for the month of December 2019 through February 2020 and compared their findings to records from the five prior years.

"With the outpatients, I found a 50% increase in the percentage of patients coming in complaining of a cough. It came out to over 1,000 extra patients above the average of what we would typically see," Elmore said.

The number of patient visits to the ER for respiratory complaints, as well as the number of people hospitalized with acute respiratory failure between December 2019 and February 2020, showed a similar increase compared to records from the past five years. The uptick in cases started in the final week of December.

"Some of these cases could have been due to the flu, some could be for other reasons, but to see these kinds of higher numbers even in the outpatient setting is notable," Elmore said.

While scientists may never know for sure if these excess patients were early Covid-19 cases, Elmore doesn't think it's out of the question.

"Our world is so interconnected. There are about 500 flights from China a month to LAX, so you could easily have one or two cases from that travel and it could get into the community," Elmore said.

Elmore hopes this research shows that real time data collected on diseases like this could potentially help public health experts identify and track emerging outbreaks much earlier and potentially slow or stop the spread of disease.

"Based on what we know of a few other studies and now this one, I think definitely this could be something," Hoyen said. "It's certainly something that needs to be considered."

Hoyen said the bigger takeaway from this study for her was that it points to the possibility that data like this could augment some of the disease surveillance the CDC is already doing for diseases like flu.

"Is there a way to mine the data in other ways that may have picked up on some of the other symptoms that people were presenting with, so we had a better understanding of disease sooner?" Hoyen asked. "Then maybe instead of a month into it, like when we were seeing a lot of patients complaining of loss of taste and smell, if we had analyzed the data beforehand, we may have picked up those kinds of symptoms much sooner."

"We know from the SARS-CoV-2 genetic data that the pandemic started in late November / early December in China so there's absolutely no way the virus could have been spreading widely in December 2019. From the same genetic data we know that widespread transmission didn't start in the United States until (around) February 2020," Andersen said in an email.

"The paper is picking up spurious signals and the hospitalizations are more likely from flu or other respiratory diseases," Andersen wrote. "Again, the genomic data clearly shows that there was no widespread transmission of SARS-CoV-2 in the United States in December of last year - there may have been a few sporadic cases, but that's it and certainly not something that would have been seen in 'excess hospitalizations.'"

"If we had more precise genetic phylogenetic data of the spread of the virus, I think that could be very interesting, but in the absence of that, you can do a lot of work by inferring some preexisting patterns from these types of analyses," said Marrazzo, the director of the division of infectious diseases at the University of Alabama at Birmingham School of Medicine. "Primary care data like this is useful and we really need to pay attention to it."

"When you compare these numbers to previous years, there's no good explanation in my mind why all of the sudden you would see that dramatic increase in the records, except for Covid," Marrazzo said. "Just the strength of the numbers of information, when you include the outpatient, it shows a pattern."

Neither the CDC nor the WHO responded to CNN's request for perspective on the research or on the official time line of the pandemic.

Marrazzo said she and infectious disease colleagues across the country have been discussing how often they were seeing patients with what we now know as Covid-19 symptoms earlier than the official timeline. Because of the sharp restrictions the CDC placed on testing early in the pandemic, it was difficult to confirm if respiratory cases they were seeing were caused by coronavirus.

"I have no doubt that we all missed cases in the early part of the pandemic," Marrazzo said. "This study offers a really interesting window into what might actually have been happening."

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Study hints Covid-19 may have been in the US as early as December - CNN

PORTSMOUTH Influenza and COVID-19 resemble each other in symptoms, and it is possible for people to contract both illnesses at the same time, so the medical community is urging everyone to get a flu vaccine to help minimize what could be a terrible season.

While there is no preventive measure yet for COVID-19, doctors say getting a flu shot has taken on an even stronger importance this year.

"We know the season will be bad," said Dr. Travis Harker, chief medical officer at Appledore Medical Group in Portsmouth, and a family practice physician. "One thing we know for sure is that COVID-19 is most deadly when the system is overwhelmed. If we do not do all we can, our hospitals are going to be filled with cases of both illnesses."

Dr. Kasra Djalayer, an internist with Greater Seacoast Community Health, which includes Families First and Goodwin Health, said the overlap of coronavirus and flu is concerning to many epidemiologists.

"Both can cause severe epidemic and can cause death," said Djalayer. "That causes a double burden on the health care system. The risk of co-infections gets higher when two viruses are circulating in the same region. Anybody can get co-infected at the exact same time. Whatever happens, there is one important step people can take that may change the trajectory of either epidemic: Get the flu vaccine."

"Even before the COVID-19 pandemic, receiving a flu vaccine each flu season has been highly recommended," said Dr. Irene P. Rupp Hodge, an infectious disease doctor, and the medical director of Frisbie Memorial Hospitals Center for Wound Care and Hyperbaric Medicine. "This certainly will remain the case for the upcoming flu season. By wearing masks, avoiding contact with people when sick, and utilizing the flu vaccine as recommended, this should reduce the spread of influenza this season, which will be a benefit to the public's health in general and will free up resources to continue to combat the COVID-19 pandemic."

Djalayer said influenza occurs in epidemics nearly every year. According to the Centers for Disease Control and Prevention, during the 2017-2018 flu season, 61,000 Americans died.

"Influenza virus is capable of changing its structure and genetic composition in a process called mutation," said Djalayer. "Due to the high rate of mutation, it compromises our immune system to fight against the new virus. For this reason, new vaccines are produced every year in order to stimulate our immune system to fight against the influenza virus with new genetic composition. We need to vaccinate people every year because the immunity slowly vanishes during the year."

Harker said the precautions being taken against COVID-19, masking, good hand hygiene and social distancing should help, even in preventing some flu cases, but he said he hopes people take the extra step and get the flu vaccination.

"One thing we know for sure is that the vaccination can help minimize the impact of influenza," said Harker. "That might also help minimize the COVID impact."

Martha Wassell, MPH, director of infection prevention at Wentworth-Douglass Hospital, said that even those people who might not have gotten the flu shot in past years should do so now.

"For whatever reason you didnt in the past, now is the time to change your behavior," said Wassell. "Its the right thing to do for you and for those around you, especially if we do encounter the perfect storm of both illnesses striking at once."

Wassell said to her knowledge a person with both viruses has not yet been seen, but she imagines it will be, and it will be bad.

"I would dread that day," said Wassell. "I would assume this would overwhelm the person who is host to both illnesses."

While the two illnesses can look very similar, Harker said testing can determine which illness a person is experiencing.

"We have set up protocols to manage both illnesses and do the testing for diagnosis," said Harker. "Schools are going to pose a unique challenge this season and will have a low threshold for sending people home during this uncertain time."

"They will need to use good judgment. Its challenging, especially with young elementary school-aged children, who may not really understand the need for the precautions that are necessary. I have been impressed in my practice, seeing children as young as two, wearing a mask because they do not want to bring the illness home to grandma."

Harker said Black and Latino populations are seeing five times the amount of COVID-19 cases as other populations.

"Black people represent four times the death rate, and Latinos, two times the death rate," said Harker. "I think part of the answer is systemic racism, housing, and education opportunities, but thats not the only reason. These populations are having a higher risk of comorbidities like diabetes and high blood pressure. COVID-19 is spread through the respiratory system, but it also attacks the blood vessels, so these comorbidities put them at a higher risk."

Harker said its not too early to get the flu shot, and he said the shot is safe. It is too early to gauge the effectiveness of this years shot or how bad the season will be, according to Harker.

The CDCs Advisory Committee on Immunization Practices recommends influenza vaccination for all individuals 6 months of age and older, for all healthy non-pregnant adults less than 65 years of age as well as for individuals over or at the age of 65. Patients with a history of Guillain-Barre Syndrome, who are pregnant or are immunocompromised, or have a history of egg allergy should consult their primary care doctor before getting the flu shot.

Harker said the population who cannot get a flu shot is small, but that if everyone else gets one, herd immunity may protect those people.

Djalayer noted flu shots are offered in many doctors offices, pharmacies, clinics, health departments as well as by many employers, and even in some schools.

"We need to be as ready as we can," said Harker. "If things go south, we may need to lock down again. If we take the right steps up front, we may be able to avoid that and we can get through this upcoming very challenging season. If most people do the right thing, we should be OK."

One more very important point, raised by Wassell, is people getting the flu shot and doing what they can to protect themselves and others could have an added bonus.

"It could help protect valuable resources we may need to deal with both illnesses," said Wassell. "It can preserve space, beds, resources and staff we may need soon. If we can directly reduce the percentage of people getting the flu, we will be better able to handle whatever does come down the road."

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Overlap of flu and COVID-19 this winter worries Seacoast medical community - Foster's Daily Democrat

Bernat Armangue/Associated Press

The concept of herd immunity is at the heart of global vaccination efforts and discussions about next steps in fighting the Covid-19 pandemic and bringing back economies.

For the pandemic to stop, the coronavirus has to run out of susceptible hosts to infect. Herd immunity occurs when enough people in a population develop an immune response, either through previous infection or vaccination, so that the virus cant spread easily and even those who arent immune have protection.

To reach herd immunity for Covid-19, public-health authorities estimate that around 60% to 70% of a given population would need to develop an immune response to the virus. Some epidemiologists and mathematicians now say herd effects might start to kick in before that point, at perhaps closer to 50%, suggesting potential protection could be achieved sooner.

Still, infectious-disease experts adamantly warn against the notion of trying to reach herd immunity to the coronavirus without a vaccine, as the costs on human life would be staggering and it likely wouldnt happen soon, if at all.

Even with a vaccine, there will still be barriers to achieving herd immunity.Its a continuous process, said Saad Omer, director of the Yale Institute for Global Health. You could start seeing [an effect] before that threshold, but the other issue is there might still be outbreaks at a smaller level.

Its not like when herd immunity is achieved, were not going to have Covid-19,he said.

Estimates vary widely for where the herd-immunity threshold lies because researchers use a variety of statistical techniques to account for differences in individuals likelihood of spreading the virus.

The herd-immunity threshold is mathematically dependent on the infectiousness of the virus, or how many individuals each infected person goes on to infectcalled the basic reproductive number, or R0. Scientists calculate the herd threshold using that number and an equation formulated almost 100 years ago by two pioneering Scottish epidemiologists.

Measles, for example, is extremely contagious. It has a basic reproductive number between 12 and 18 and a herd threshold of 90% to 95%. For SARS-CoV-2, the basic reproductive number is estimated at around 2.5 to 3, implying a herd threshold of 60% to 70%.

But the classic equation makes an assumptionthat everyone is equally susceptible to infection and has the same chance of bumping into every other person, like molecules of gas in a bag, said Justin Lessler, associate professor of epidemiology at Johns Hopkins Bloomberg School of Public Health.

Which of course is ridiculous. Its not how the world works, Dr. Lessler said. The equation gives you a good target for vaccine coverage, but it doesnt capture the dynamics of an epidemic moving naturally from person to person, he said.

In reality, people live in clusters, interacting only with certain individuals. Age, job, social network and even individual biological responses to infection all affect a persons place in the spidery web of disease transmission.

Essential workers, for instance, are more likely to get infected than people able to limit interactions with others. If those who are more likely to transmit the virus developed immunity early on, whether through infection or vaccine, it would be possible to start seeing a reduction in transmission earlier, epidemiologists say.

Reflecting these real-world effects in disease models can shift the estimated herd immunity boundary. One group of researchers estimated that threshold for Covid-19 could be as low as 10% to 20%, though many epidemiologists say that is unlikely. Other modelers have estimated it at around 40% to 50%. Christopher Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington, said his group estimates the herd-immunity threshold at between 50% and 80%.

If lower estimates for herd immunity are correct, then governments should consider policies to shield the elderly and other at-risk groups from the virus while relaxing restrictions on everybody else, said Paul McKeigue, professor of genetic epidemiology and statistical genetics at the University of Edinburgh, in Scotland.

But most infectious-disease experts strongly advise against that, as it isnt clear how governments would shield more vulnerable people from the easily spread pathogen. Those in lower-risk groups can become seriously ill and, on rare occasions, die as a result of the disease. Doctors are just beginning to understand long-term health effects.

If were talking about letting the disease run its course [and] infect large numbers of people, essentially what were saying is the public-health system has failed to do its job, said Nadia Abuelezam, an infectious-disease epidemiologist at Boston College. Well have a lot of death, and well have a lot of morbidity.

Communities, including some neighborhoods in New York, and even individual families that have been hard-hit by the virus likely do have an elevated level of protection. But its a dangerous thing to base your strategy on, said Dr. Omer. Theres still enough tinder to be burned.

Most places arent likely near the point where everyone is protected, even as confirmed global infections surpass 30 million and deaths top 950,000.

And even if subpopulations do develop a level of protective immunity, the virus can easily jump to unexposed pockets, especially if restrictions are relaxed and people potentially start to socialize and travel more, epidemiologists say.

In places where cases have slowed, behavioral changes such as mask-wearing and social-distancing are the more likely explanations for reduced transmission, said Natalie Dean, a biostatistician who specializes in infectious diseases at the University of Florida.

Sweden, for instance, which didnt implement an aggressive lockdown, still has bans on gatherings of more than 50 people, among other restrictions and voluntary guidelines.

A preliminary survey from the Swedish Public Health Agency in May showed that only 6.7% of people from ages 20 to 64 and 2.7% of those from ages 65 to 95 had antibodies. Sweden also has the highest per capita death rate of its Nordic neighbors.

At this point, I would not bank on herd immunity in most areas on this planet, Florian Krammer, a professor in vaccinology at the Icahn School of Medicine at Mount Sinai in New York, said during a panel recently at the online Aspen Ideas health festival.

Another wrinkle: Infectious-disease experts arent sure how long immunity to the virus might last, or how often re-infections might occur. Past exposure to other coronaviruses might provide some protection, though any effects of that are unclear.

For diseases such as measles, mumps and polio, herd immunity was achieved through vaccination campaigns. Many say the Food and Drug Administration could authorize a Covid-19 vaccine by year-end, but the rollout will likely be staggered well into 2021, incrementally reducing the susceptibility of the population and building up resistance.

And even when one does potentially become available, there are growing concerns that some Americans wont want it.

How much of the population needs to get vaccinated to help achieve herd immunity also depends on a potential vaccines effectiveness. The FDA has said it would authorize a vaccine with 50% efficacy or better. Some vaccines could require more than one dose to build up a robust response.

The coronavirus is unlikely to disappear completely, public-health experts say. More likely, there will be outbreaks in vulnerable pockets that authorities will work to control, similar to measles, or it could circulate similarly to influenza.

But public-health precautions such as mask-wearing can beat back the virus and, coupled with widely administered vaccines, safely help a level of normalcy return, health authorities say.

With a combination of a good vaccine together with good public-health measures, we may be able to put this coronavirus outbreak behind us, Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told The Wall Street Journals CEO Council on Wednesday. There will be an end to this, and we will be able to get back to normal.

Write to Brianna Abbott at brianna.abbott@wsj.com and Jason Douglas at jason.douglas@wsj.com

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What It Would Take for Herd Immunity to Stop the Coronavirus Pandemic - msnNOW