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Advice is evolving along with the coronavirus. Here's the latest from staff and wire reports.

Where can I see Minnesota's COVID-19 numbers?

Check our COVID tracker.

What is the new omicron COVID variant?

It's unclear where the omicron variant, named B.1.1.529,actually arose. It has popped up in several countries, including the United States, as well as in Minnesota.

Much remains unknown, including whether the new variant is more contagious, as some health authorities suspect, whether it makes people more seriously ill, and whether it can thwart the vaccine.

How did the new omicron variant get its name?

The omicron variant was named after the 15th letter of the Greek alphabet. The naming system, announced by the World Health Organization in May, makes public communication about variants easier and less confusing, the agency and experts said.

There are now seven "variants of interest" or "variants of concern," and they each have a Greek letter, according to a WHO tracking page. Read more here.

Where can I get a vaccine?

Check the state of Minnesota's Vaccine Connector or the national Vaccine Spotter.

How can I make a COVID-19 vaccine appointment for kids in Minnesota?

Minnesota has launched a webpage (mn.gov/vaxforkids) to help parents and guardians find a vaccine and answer questions.

More than 1,100 Minnesota providers, including pediatricians, pharmacies, local public health agencies and schools, are able to provide vaccines to children. Read more here.

What do federal regulators say about vaccines for kids?

The CDC on Nov. 3 cleared kid-size doses of Pfizer's COVID-19 vaccine for children ages 5 to 11. Pfizer has additional studies underway in those younger than 5.

U.S. regulators are delaying their decision on Moderna's COVID-19 vaccine for 12- to 17-year-olds while they study the rare risk of heart inflammation. The company also said it will delay filing a request for emergency-use authorization of a lower dose of the vaccine for 6- to 11-year-olds.

How often do COVID vaccines cause heart problems in kids?

While the COVID-19 vaccines made by Pfizer-BioNTech and Moderna do seem to be associated with an increased risk of myocarditis, the latest data indicate that the absolute risk remains very small and that most cases are mild and resolve quickly.Read more here.

Is travel safe during the pandemic this holiday season?

The U.S. Centers for Disease Control and Prevention says not to travel if you're sick, or if you tested positive for COVID-19 and your isolation period isn't over yet — even if you're fully vaccinated. Unvaccinated people who decide to travel should get a COVID-19 test one to three days before travel and three to five days after returning.

All travelers must still wear masks on trains, planes and other indoor public transportation areas, the agency says. Read more here.

Is there a decline in the effectiveness of COVID-19 vaccines over time?

As the delta variant became the dominant strain across the United States, all three COVID-19 vaccines available to Americans lost some of their protective power, according to a study published Nov. 4 in the journal Science.

Researchers who scoured the records of nearly 800,000 U.S. veterans found that in early March, the three vaccines were roughly equal in their ability to prevent infections.

By the end of September, Moderna's two-dose COVID-19 vaccine, measured as 89% effective in March, was only 58% effective.

The effectiveness of shots made by Pfizer and BioNTech vaccine, which also employed two doses, fell from 87% to 45% in the same period.

And most strikingly, the protective power of Johnson & Johnson's single-dose vaccine plunged from 86% to just 13% over those six months.

What about booster shots?

The CDC is now recommending booster shots for all vaccinated people 18 and older.

Anyone 18 or older can choose a Pfizer or Moderna booster six months after their last dose. For anyone who got the single-dose Johnson & Johnson vaccine, the wait already was just two months. And people can mix-and-match boosters from any company.

The CDC said older Americans and people with risks such as obesity, diabetes or other health problems should try to get a booster before the holidays.

Experts agree that getting a booster too soon can reduce the benefit.

Should you mix or match your COVID-19 vaccine booster shot?

Public health officials have declined to recommend a specific shot, leaving it up to individuals to decide. Here's a look at the science behind mix-and-match boosters and some advice from the experts to help you decide.

Am I fully vaccinated without a COVID-19 vaccine booster?

Yes. The CDC says you're fully vaccinated two weeks after receiving a second dose of the Pfizer or Moderna vaccine, or one dose of the Johnson & Johnson.

Where can I get tested?

Minnesota has several free COVID-19 testing sites that offer saliva and/or rapid tests. Minnesotans may alsoorder a free test through the state's at-home COVID-19 testing program. Health care providers and some pharmacies also offer testing. You may find home rapid tests at pharmacies including Walgreens and CVS, although supplies are sometimes limited.

Must the swab go that far up your nose to test for COVID-19?

Wariness about the test may arise from a simple fact: Most people cannot stand having something shoved so far up their nose.

Pain enters the picture when the swab — a tuft of nylon attached to a lollipop-like stick — is administered at the wrong angle, said Dr. Yuka Manabe, a professor of medicine specializing in infectious diseases at Johns Hopkins University School of Medicine. Read more here.

Is there a federal vaccine mandate?

It's on hold indefinitely because of legal challenges, but employers can still require the shots.

President Joe Biden said businesses with 100 or more employees would need to require COVID-19 vaccination or have workers get tested weekly for the virus. The rule was to take effect Jan. 4, affecting about 84 million workers nationwide.

But soon after the rule was issued by the U.S. Occupational Safety and Health Administration, it faced legal challenges from businesses, conservative groups and Republican attorneys general that said the agency doesn't have the authority to mandate vaccines.

On Nov. 6, a federal appeals court in New Orleans put the rule on hold, saying it was "a one-size fits-all sledgehammer" that was too broad. Ten days later, all challenges to the requirement were consolidated in another appeals court in Cincinnati.

A federal judge on Dec. 7 blocked the administration from enforcing a vaccine mandate for employees of federal contractors.

What would the mandate mean for Minnesota employers?

In Minnesota, the new orders would affect about 4,800 businesses that employ about 1.4 million Minnesotans. That is about half of the state's total workforce.

Can I get a vaccine incentive?

Gov. Tim Walz unveiled a $100 incentive for vaccine recipients at select clinics and health centers in communities hit hardest by the pandemic. The incentives will total $100 in value but could range from Visa gift cards to grocery store vouchers.

Ramsey County announced a $100 Visa gift card program for people who get their first shot at a clinic operated by theSt. Paul-Ramsey County Public Health Department. The program is open to everyone, regardless of county residence.

Hennepin County is offering $50 Visa gift cards per shot to anyone who gets vaccinated at a Hennepin County vaccine clinic or event, while supplies last.

Is it a cold, the flu or COVID-19?

The illnesses come from distinct viruses but often have similar symptoms. Some of the signs that COVID-19 and the flu share include fever, cough and chills. The common cold is usually milder than the flu, with a runny or stuffy nose more likely.

The loss of taste or smell - a possible COVID-19 symptom - can help set it apart, although people with allergies or stuffy noses might find it harder to smell, too. Those with coronavirus can also take more time to show symptoms and be contagious for longer than people with flu infections. Read more here.

Is the coronavirus getting better at airborne transmission?

Newer variants of the coronavirus such as alpha and delta are highly contagious, infecting far more people than the original virus. Two new studies offer a possible explanation: The virus is evolving to spread more efficiently through air. Read more here.

What is a COVID-19 vaccine "breakthrough" case?

It's when a fully vaccinated person gets infected with the coronavirus. While the vaccines are very good at protecting us, it's still possible to get infected with mild or no symptoms, or even to get very sick. If you do end up getting sick despite vaccination, experts say the shots help reduce the severity of the illness. But one question that remains unanswered is: Can the vaccinated develop so-called long COVID?

How can I tell if I have a breakthrough infection?

Most people will struggle to know for sure based on symptoms alone, without a nose swab to rule out the coronavirus. And if vaccinated people test less often, COVID infections could get dismissed as mild colds or go unnoticed.

British scientist Tim Spector, a founder of the ZOE app that tracks coronavirus symptoms, has said that people thinking they have colds when they really have COVID-19 could help fuel the pandemic. Read more here.

What is the breakthrough rate in Minnesota?

Minnesota on Nov. 29 reported a total of 94,671 coronavirus infections in fully vaccinated people, including 655 people who died of COVID-19. Although the breakthrough total represents only 2.9% of Minnesota's 3.3 million fully vaccinated individuals, the rate has been increasing.

Vaccinated people with COVID-19 are taking up more hospital beds, but data from the Allina Health and HealthPartners hospital systems show that they often have milder illnesses that don't require intensive care.

Do I still need to get a flu shot?

Many officials and experts are urging the public: Do not dismiss the danger of the flu, and seek a flu vaccine. "This year we are guaranteed to have the flu, and we are going to have some version of a twindemic," said Dr. William Schaffner, medical director for the National Foundation for Infectious Diseases. Read more here.

Are the vaccines approved by the FDA?

The U.S. gave full approval to Pfizer's vaccine on Aug. 23. The formula, jointly developed with Germany's BioNTech, will be marketed under the brand name Comirnaty.

Moderna has also applied to the FDA for full approval of its vaccine. Johnson & Johnson, maker of the third option in the U.S., said it hopes to do so later this year.

Are the vaccines safe?

A review of 6.2 million vaccine recipients in Minnesota and seven other U.S. regions found no significantly elevated rates of conditions such as stroke or heart attack immediately following COVID-19 vaccination. Bloomington-based HealthPartners participated in the study, which looked for elevated rates of 23 potential side effects in the first three weeks after people received Pfizer or Moderna COVID-19 vaccines.

Who qualifies for an extra shot?

Federal officials approved a third dose for those undergoing cancer treatment, who've received organ transplants or had other conditions that depress the body's immune system. These doses are not considered to be boosters.

Can kids get "long COVID" after coronavirus infections?

Yes, but studies indicate they're less likely than adults to be affected by symptoms that persist, recur or begin a month or more after infection.

A recently published U.K. study found about 4% of young children and teens had symptoms more than a month after getting infected. Fatigue, headaches and loss of smell were among the most common complaints and most were gone by two months. Coughing, chest pain and brain fog are among other long-term symptoms sometimes found in kids, and can occur even after mild infections or no initial symptoms.

Some studies have found higher rates of persisting symptoms than in the U.K. study.

Experts aren't sure what causes the long-term symptoms. In some cases, it could reflect organ damage caused by the initial infection. Or it could be a result of the virus and inflammation lingering in the body.

Kids can develop other rare problems after a coronavirus infection, including heart inflammation or a condition known as multisystem inflammatory syndrome. Because of the potential for long-term consequences, the American Academy of Pediatrics recommends follow-up doctor visits after children recover from an initial coronavirus infection.

What about adults and long COVID?

About 30% of adult COVID-19 patients develop long-term symptoms, according to some estimates.

A new study of Long Beach residents found that one in three people who survived COVID-19 suffered from long COVID. There were higher rates among people 40 or older, women, people with preexisting health conditions and Black residents. Fatigue was reported by 17%; difficulty breathing and loss of taste or smell were reported by 13%; and muscle or joint pain was reported by 11%.

What does the CDC say about masks?

The Centers for Disease Control and Prevention (CDC) recommends that even fully vaccinated people wear masks in areas with high or substantial levels of viral transmission.

Unvaccinated people are urged to wear masks in indoor public settings, social engagements and crowded outdoor settings.

When can we stop wearing masks?

Many Americans are wondering when masks might finally come off. That time has not yet come, experts said. It will be safer to ease mask requirements early next year, scientists said, after more children have been fully vaccinated and the holiday travel season has passed. And voluntary mask-wearing will continue to be helpful in certain circumstances, as well as in future cold and flu seasons, they noted. Read more here.

Do masks work?

Ordinary surgical and paper masks work when worn properly, said Chris Hogan, a University of Minnesota researcher who has studied mask effectiveness and is editor of the Journal of Aerosol Science.

Generally, the CDC says masks should have two or more layers of "washable, breathable fabric" that completely covers your nose and mouth.They should "fit snugly against the sides of your face" with no gaps and have a wire that bends over your nose to prevent air leakage out the top.

The CDC says you should avoid masks made of fabric that makes it hard to breathe, that have exhalation valves or vents and N95s labeled as "surgical" or "medical" masks to prioritize them for health care workers.

If you decide to keep wearing your multi-layer homemade or cloth mask, experts advise washing them every day. But proceed with caution. Read more here.

How do Pfizer and Moderna vaccines compare?

In a half-dozen studies published over the past few weeks, Moderna's vaccine appeared to be more protective over the long term than the Pfizer-BioNTech vaccine.

What is the Docket app?

Minnesota introduced the Docket app for viewing personal immunization records in response to rising demand — largely because of more COVID-19 vaccination requirements by employers and organizations. State leaders said this is not a prelude toward a COVID-19 vaccine passport or government vaccination requirement.

How prevalent is the delta variant?

The extremely transmissible delta variant of the coronavirus, which overtook all other variants in the United States just a few months ago, now represents more than 99% of cases tracked in the country, according to the data from the CDC.

Where do I need to wear a mask?

Minnesota required mask wearing for its workers in state government buildings, a day after St. Paul, Minneapolis, Hennepin County and Ramsey County required masks for workers and visitors in their buildings.

Minneapolis and St. Paul mayors encouraged people in the Twin Cities, regardless of their vaccination status, to wear them indoors.

Anybody 2 years old and over in Brooklyn Center must now wear a mask in city facilities and city schools. The suburb also enacted a health emergency, allowing it to enact pandemic emergency plans if needed, which will remain in effect until the City Council takes action to end it.

Target, Cub Foods and other retailers require masks for employees and encourage them for customers in areas with high coronavirus transmission levels.

Some businesses such as Juut Salon Spa, as well as employers such as Wells Fargo and the Star Tribune, are requiring visitors and workers to wear masks again. U.S. Bancorp requires masks for unvaccinated employees and "strongly" encourage them for the vaccinated. Starkey Hearing Technologies told all workers to wear masks in common areas and unvaccinated employees to also wear masks at their desks.

Amazon requires all of its 900,000 U.S. warehouse workers to wear masks indoors, regardless of their vaccination status.

The Minnesota Children's Museum requires masks for all visitors age 5 and up. Others requiring masks include the Minnesota Lynx, Guthrie Theater, Minnesota Orchestra, Walker Art Center, History Theatre, Park Square Theatre, Shubert Club, Renegade Theater and the Arts Partnership — made up of the Minnesota Opera, the St. Paul Chamber Orchestra, the Ordway and Schubert Club. Hennepin Theatre Trust — which operates the Orpheum, State and Pantages theaters in downtown Minneapolis — requires guests to wear masks inside all the venues except when eating or drinking, as does the Dakota.

Can employers mandate the vaccine?

FDA approval for Pfizer's COVID-19 vaccine sets the stage for employers across Minnesota to push harder for workers to get immunized.

Even before the regulatory action, immunization mandates were possible, attorneys say, so long as companies, universities and local governments provided exemptions to workers with religious or medical objections.

Are employers mandating the vaccine?

Some workplace policies are making it more of a hassle for workers to resist the vaccine. Others culminate in unvaccinated employees losing their jobs.

Hennepin County will require its nearly 9,000 employees to get vaccinated against COVID-19. Ramsey County requires its 4,00 employees to provide proof of vaccination or submit to regular testing.

St. Paul Mayor Melvin Carter said nearly every city employee will be required to have their shots completed by the end of the year. St. Paul will make exceptions for those who qualify for medical accommodations or religious exemptions.

A spokesman for Minnetonka-based UnitedHealth Group said a vaccination requirement applies to a "significant portion" of the roughly 220,000 employees in the U.S., including about 18,000 in Minnesota. Workers must be vaccinated by Nov. 30 and may request exemptions for medical or religious reasons.

St. Paul Public Schools and Minneapolis Public Schools requires employees to be vaccinated or tested weekly beginning Oct. 15. Instead of showing proof upfront, St. Paul staff members will fill out a form and then be subject to potential audits later.

Intermediate School District 287, a cooperative serving about 1,000 high-needs kids in Hennepin County, said it will require staff members to participate in weekly COVID-19 testing or show proof of vaccination.

Minneapolis Mayor Jacob Frey signed anemergency regulationrequiring city employees to get vaccinated or get tested regularly.

The Star Tribune will require employees who report to work onsite or work with the public to be vaccinated, with an accommodation request process for medical or religious reasons.

Minnesota government employees returning to the office must prove they've been vaccinated or comply with at least weekly testing. The mandate applies to roughly 50,000 people who work under the umbrella of state government and on Minnesota State campuses.

Changes are prominent in health care. Mayo Clinic said workers throughout the Rochester-based health system must get vaccinated or go through an hourlong education session. Essentia Health will require all employees to be fully vaccinated by November. With few exceptions for medical and religious reasons, the mandate applies to all 13,000 of the Duluth-based health system's employees in Minnesota, Wisconsin and North Dakota. Sanford Health is requiring all workers to get shots by Nov. 1.The Fairview and Allina health systems announced vaccine requirements with some exceptions for their workers.

President Joe Biden said his administration will require that nursing home staff be vaccinated as a condition for those facilities to continue receiving federal Medicare and Medicaid funding.

The Federal Reserve Bank of Minneapolis said it would require its 1,100 employees to get vaccinated by the end of August. Minneapolis law firm Robins Kaplan also has a vaccine mandate.

The federal Health and Human Services Department is requiring employees who provide care or services for patients to get their shots. The order from Secretary Xavier Becerra will affect more than 25,000 clinicians, researchers, contractors, trainees and volunteers with the National Institutes of Health, the Indian Health Service and the U.S. Public Health Service Commissioned Corps. The VA ordered its health care workers to get vaccinated.

Walmart is requiring that all workers at its headquarters as well as its managers who travel within the U.S. be vaccinated against COVID-19 by Oct. 4.

Delta Air Lines employees on Delta's health plan who haven't been fully vaccinated will incur a $200 monthly surcharge, deducted from paychecks beginning in November. Unvaccinated employees will immediately be required to mask up at indoor Delta facilities. And beginning Sept. 30, COVID-19 pay protection applies to fully vaccinated employees who suffer a breakthrough infection. The new policies don't apply to regional airline partners, including Minneapolis-based Endeavor Air, that operate under the Delta Connection name.

United, Hawaiian and Frontier airlines said all employees must soon be vaccinated, with certain exemptions available. Twin Cities-based Sun Country doesn't require its employees to be vaccinated, "but we are encouraging it," a spokeswoman said.

Medtronic, which has its operational headquarters in Fridley, said workers need to be vaccinated or have a recent negative test result to enter U.S. offices.

Members of the U.S. military were required to get the COVID-19 vaccine beginning in September, as were employees of the Pentagon.

What about entertainment venues?

Audience members have to show proof of full COVID-19 vaccination or negative test results to get into a show at First Avenue or any of its sister venues, the Dakota, the Cedar Cultural Center, the Ordway, the Guthrie Theater, Minnesota Orchestra, Walker Art Center, History Theatre, Park Square Theatre, Shubert Club and Hennepin Theatre Trust's Orpheum, State and Pantages in downtown Minneapolis. Renegade Theater Company will require proof of full vaccination or a recent negative test to attend its performances at Zeitgeist Teatro Zuccone in Duluth

Promoter Live Nation is also enforcing a vaccine/test requirement at all its indoor venues, including the Fillmore and Varsity Theater in Minneapolis, as is the Uptown VFW aka the James Ballentine VFW Post 246.

The Armory in Minneapolis does not have a standard policy. Attendees are being told to checkarmorymn.comto find out whether each show has rules in place.

Which Twin Cities area restaurants require proof of vaccination?

A small but growing number of restaurants including the Dakota and Hark! Cafe in downtown Minneapolis and W.A. Frost in St. Paul are asking indoor patrons to show proof of vaccination or a negative COVID tests. Check out our updating list here.

What if I'm going to Canada?

The Canadian government requires travelers to be vaccinated.

What are Minnesota K-12 schools doing?

The CDC recommended that people wear masks in K-12 schools and in counties with high or substantial levels of viral transmission.

State health and education officials are recommending — but not requiring — that Minnesota school districts mandate indoor mask wearing for all students and teachers this fall, whether or not they have received a COVID-19 vaccine.

Because Gov. Tim Walz no longer retains the emergency powers that allowed the state to mandate mask wearing earlier in the pandemic, decisions about masking, social distancing and other precautionary measures will be left to local school districts. Only two statewide requirements remain: Schools must report all confirmed COVID-19 cases to the state, and students and staff must wear masks while on school buses, in line with federal guidelines for public transportation.

Free COVID-19testing kitswill be offered to schools as will grant money to help with supplies and staffing support, state officials said.

The Minneapolis School District has become what's believed to be the first in the state to require unvaccinated high school athletes to be tested weekly for COVID-19.

Anoka-Hennepin, the state's largest district, has mandated masksfor staff and students in kindergarten through sixth grade when county health department data reaches a particular threshold: at least 15 cases per 10,000 residents. Masks will be recommended, but not required, for students in grades 7 to 12 and staff and visitors working with those students.

A growing number of Minnesota districts, including St. Paul, Minneapolis, Brooklyn Center, Osseo, Roseville, Duluth, St. Cloud and Edina, are requiring masks for everyone inside all school buildings. Others are requiring masks only for grade levels with students too young to qualify for a COVID-19 vaccine. That includes Mankato, Minnetonka and South Washington County schools.

Albert Lea Area Schools required masks for grades 6-12 after 36 cases of COVID-19 and 290 students in quarantine just five days after classes started on Aug. 19.

St. Paul Public Schools said a new online school initially designed for high schoolers will now include students from kindergarten through grade 12.

The Elk River district said in mid-July that masks would not be required, and did not make any specific recommendations. Wayzata's current back-to-school plan says masks are optional, but district officials said they are reviewing the new recommendations and will update families of any changes.

Other districts have specific plans for students too young to be vaccinated. In Rochester, school board members voted to require people under age 12 to wear masks. Mask wearing is recommended for older students and adults there, regardless of their vaccine status.

What are Minnesota colleges and universities doing about masks and vaccinations?

The University of Minnesota, University of St. Thomas, Hamline University, St. Catherine University, Macalester College, Augsburg University, Carleton College, St. Olaf College, the College of St. Benedict, St. John's University, Gustavus Adolphus College and the Mitchell Hamline School of Law will require vaccinations for students, joining hundreds of schools nationwide.

The University of Minnesota said all students, employees and visitors at its five campuses are required to wear masks indoors. Minnesota State Chancellor Devinder Malhotra told presidents of the system's 37 colleges and universities they should reinstate indoor mask mandates if they are located in counties with high virus transmission. The system will require certain students — such as those living in dorms or on sports teams — to be vaccinated or tested regularly.

Are Minnesota employers bringing workers back to the office?

With vaccinations rising, Twin Cities employers are starting to usher thousands of workers back into the office. Read more here.

Best Buy and U.S. Bank are among those enacting back-to-office plans. Graco, Ameriprise and Abbott Laboratories brought workers back, starting in the summer. On Nov. 22, several hundred of Ernst & Young's 800 Minneapolis workers showed up for their first day inside the accounting firm's space in the Dayton's Project building on Nicollet Mall.

Target is creating "flex floors" at its Minneapolis and Brooklyn Park campuses and opening a new Eagan site for workers who want a transitional space to do in-person or virtual work.

Companies with sizable downtown offices such as Target, Thrivent, Ernst & Young and Fredrikson & Byron say they have embraced a hybrid work model that will allow many office workers to return to the office part time and work remotely from home some days a week even after the pandemic ends.

Who can make you get a COVID vaccine?

A growing number of employers, universities and businesses are now issuing some form of a vaccine requirement. (Here's a look at who could ask you to get the vaccine.)

Under many of these orders, those who remain unvaccinated, including people who can't get a vaccine because of a disability or conflicting religious beliefs, will instead have to follow strict guidelines like regular COVID testing, masking and social distancing.

"I think probably what these companies are thinking — for those individuals — requiring them to be masked, or constantly tested, is a reasonable accommodation," Joel Friedman, a law professor at Tulane University, said. "And that's probably correct."

Do people who've had COVID-19 still need to get vaccinated?

Even people who have recovered from COVID-19 are urged to get vaccinated. A new study shows survivors who ignored that advice were more than twice as likely to get reinfected.

The CDC study adds to growing laboratory evidence that people who had one bout of COVID-19 get a dramatic boost in virus-fighting immune cells — and a bonus of broader protection against new mutants — when they're vaccinated.

Should pregnant women get the vaccine?

The CDC urged all pregnant women to get the COVID-19 vaccine as hospitals in hot spots around the U.S. see disturbing numbers of unvaccinated mothers-to-be seriously ill with the virus. Expectant women run a higher risk of severe illness and pregnancy complications from the coronavirus, including perhaps miscarriages and stillbirths.

A research study based on data from Bloomington-based HealthPartners and medical centers across the country finds that pregnant women who received COVID-19 vaccines did not experience an increased risk of miscarriage.

If you're thinking of getting pregnant, there's no evidence that any vaccines, including COVID-19 vaccines, influence your chances of getting pregnant despite a myth suggesting otherwise.

Do pregnant women who get vaccinated pass the protection to their babies?

Pregnant women who get mRNA vaccines pass high levels of antibodies to their babies, according to a study published in American Journal of Obstetrics & Gynecology - Maternal Fetal Medicine on Sept. 22.

The study — one of the first to measure antibody levels in umbilical cord blood to distinguish whether immunity is from infection or vaccines — found that 36 newborns all had antibodies to protect against COVID-19 after their mothers were vaccinated with shots from Pfizer-BioNTech or Moderna.

Will people need vaccine passports to do fun things?

In parts of the U.S., you might have to carry your COVID-19 vaccine card or a digital copy to get into restaurants, bars, nightclubs and outdoor music festivals. Enough venues are starting to ask for digital passes to worry some privacy advocates, who fear the trend could habituate consumers to constant tracking.

Is the delta variant more contagious?

Scientists who studied a big COVID-19 outbreak in Massachusetts concluded that vaccinated people who got so-called breakthrough infections carried about the same amount of the coronavirus as those who did not get the shots.

The research was key in the decision by the Centers for Disease Control and Prevention (CDC) to recommend that vaccinated people return to wearing masks indoors in parts of the U.S. where the delta variant is fueling infection surges.

Previously, vaccinated people who got infected were thought to have low levels of virus and to be unlikely to pass it to others. But the new data shows that is not the case with the delta variant.

The delta variant, first detected in India, causes infections that are more contagious than the common cold, flu, smallpox and the Ebola virus, and it is as infectious as chickenpox, according to the documents, which mentioned the Provincetown cases.

Delta has kept some of the most successful mutations found in earlier variants, but also contains new genetic changes that enable it to spread twice as fast. It has an incubation period of four days, rather than six, making people contagious sooner.

The delta variant was the main reason that people decided to get vaccinated against COVID-19 this summer and why most say they will get boosters when eligible, according to the latest monthly survey on vaccine attitudes by the Kaiser Family Foundation, released on Sept. 28.

The delta variant is sending more children to the hospital. Are they sicker, too?

Most children with COVID-19 have mild symptoms, and there is not yet enough evidence to conclude that delta causes more severe disease in children than other variants do, scientists said.

What is clear is that a confluence of factors — including delta's contagiousness and the fact that people under 12 are not yet eligible to be vaccinated — is sending more children to the hospital, especially in areas of the country where the virus is surging.

Is the delta variant making young adults sicker?

Physicians working in COVID-19 hot spots across the nation say the patients in their hospitals are not like the patients they saw last year. Almost always unvaccinated, the new arrivals tend to be younger, many in their 20s or 30s. And they seem sicker than younger patients were last year, deteriorating more rapidly.

Doctors have coined a new phrase to describe them: "younger, sicker, quicker." Many physicians treating them suspect that the delta variant of the coronavirus, which now accounts for more than 80% of new infections nationwide, is playing a role.

There is no definitive data showing that the new variant is somehow worse for young adults. Some experts believe the shift in patient demographics is strictly a result of lower vaccination rates in this group.

"Our sense is that younger, healthier people are more susceptible to the delta variant than those that were circulating earlier," said Dr. Cam Patterson, chancellor of the University of Arkansas for Medical Sciences.

What does the delta variant mean for herd immunity?

Herd immunity is based on the idea that when a certain percentage of the population has been vaccinated against the virus or gains immunity by a previous infection, it helps protect the broader population and reduce transmission.

The spread of the delta coronavirus variant has pushed the threshold for herd immunity to well over 80% and potentially approaching 90%, according to an Infectious Diseases Society of America briefing.

Dr. Gregory Poland with Mayo Clinic said recently he thinks that the high transmissibility of the delta variant could mean that even 95% coverage may not be enough.

What's the mu variant?

Since being discovered in Colombia in January, the mu variant has spread to nearly four dozen countries. Health officials believe mu is even more transmissible than the delta variant and has the potential to resist vaccines.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said that health officials were maintaining a "close eye" on the mu variant despite it being "not at all even close" to becoming the dominant COVID-19 strain in the U.S.

The U.S. saw its peak of mu variant cases in mid-July.

Correction: Previous versions of this story incorrectly described the Ramsey County Deputies’ Federation’s stance on a proposed COVID-19 vaccine mandate for county employees. Previous versions of this story incorrectly stated the Capella Building requires masks.