A fourth vaccine is getting closer to a meeting with the FDA to ask for emergency approval as vaccine clinics expand and supplies of other vaccines remain tight.

AstraZenica is analyzing the date collected in the U.S. and will take their findings to the FDA soon.

“Within a month, maybe sooner than that,” said Dr. Robert Frenck.

Frenck is a researcher at Cincinnati Children’s Hospital. He led the research here on the Pfizer vaccine and worked on AstraZenica study more recently.

“They have to do the analysis. They have to have enough cases to say what the efficacy was but, assuming there’s a positive there, they would be submitting the information to the FDA,” Frenck said.

AstraZenica said results from studies in the UK, Brazil and South Africa have shown its vaccine is 100 percent effective against severe cases and hospitalizations. Overall effectiveness is 82 percent after two doses.

The U.S. results have not been made public yet.

AstraZenica emerges as concerns about variants continue to grow.

“The good news is that the vaccines have shown good efficacy against the variants so far. The other thing is that these platforms, the AstraZenica, the Johnson and Johnson, as well as the MRNA vaccines are ones that can be tweaked, really very quickly,” Frenck said.

FRANKFORT, Ky. — All Kentuckians 16 and older are now eligible to receive Pfizer's COVID-19 vaccine, the only vaccine authorized by the FDA for use in people under 18. Additionally, Kentuckians 18 and up qualify for the Moderna and Johnson & Johnson vaccines.

Young people are being hospitalized with COVID-19 at greater rates in recent weeks, Gov. Andy Beshear said, and health officials are concerned that mutated coronavirus variants are spreading faster. Kentucky has identified 83 cases of the B117 variant statewide, including 13 cases in Kenton County, eight in Campbell County and seven in Boone County.

For this reason and because more vaccine appointments become available, Kentucky expanded vaccine eligibility to younger people.

"We know this is our ticket out of this pandemic, and the faster we get people vaccinated, the safer we are, the more that we can do, the more likely we fully and finally defeat COVID-19," the governor said Monday.

MORE: Where to sign up for a COVID-19 vaccine in the Tri-State

Since doses first arrived in December, Kentucky has vaccinated more than 1.4 million individuals against COVID-19, just under one third of Kentucky's total population.

After new cases of COVID-19 had declined for 11 weeks, Kentucky is now seeing new cases plateau. Kentucky's test positivity rate has continued to decline and is now 2.9%.

"Is that good or bad news? First, it's not good news if we're no longer declining. We always want to be declining... It's good news, though, that we're not escalating. But remember, other states that were declining plateaued for a period, and then increased. So we need to be vigilant. We need to be a little bit concerned," Beshear said, adding that a fourth wave can be avoided if Kentuckians follow COVID-19 precautions like masking up and social distancing.

Kentucky recorded 110 new cases Monday, lower than any of the last three weeks, as well as eight new deaths, including four audit deaths from November. Beshear said these low numbers are likely due to lab closures over the Easter weekend.

Since March 2020, 429,511 Kentuckians have tested positive for COVID-19 and 6,171 have died of the virus. Currently, 353 Kentuckians are hospitalized for COVID-19, with 97 people in intensive care units and 46 on ventilators.

The governor cautioned that Kentucky must continue to use "common sense" practices to prevent the spread of COVID-19 as other states see case numbers rising. Beshear has also discouraged "non-essential travel" during spring break, especially for people who are not vaccinated. The CDC announced that fully vaccinated people can safely travel inside the U.S.

NKY Health reports 497 active coronavirus cases in Boone, Campbell, Grant and Kenton counties, and 40,030 people have recovered from the virus Monday. Since the pandemic began, 422 Northern Kentuckians have died from the virus. Track the spread on Kentucky's COVID-19 incidence rate map.

Watch a replay of the briefing below:

As the United States continues on a path to near pre-pandemic normalcy, experts remain concerned over low vaccination rates and the spread of variants, which could potentially exacerbate a pandemic that has upended life for more than a year and inflicted a damaging toll on Americans and the world.

New York and California, which were home to some of the nation's deadliest virus hotspots last year, are fully reopening in time for the summer as Sunday marks the 500th day since the first known COVID-19 death in the U.S.

California officials announced in April 2020 that a 57-year-old woman who died on Feb. 6 that year passed away from coronavirus complications, more than three weeks before what was previously believed to be the nation's first death in Washington state.

Since then, at least 601,740 Americans have died from COVID-19, according to the most recent data from Johns Hopkins University. Recent months brought overall fewer cases, hospitalizations and deaths — progress health experts attribute to vaccines.

With more than 300 million total vaccine doses administered as of this week, the U.S. has gone through major coronavirus milestones worthy of celebration: From reporting a current seven-day moving average of 13,997 daily new cases this week compared to the peak of 251,834 cases on January 10, to administering an average of more than 3 million vaccine doses per day in April, according to data from the Centers for Disease Control and Prevention.

But there's still a long way to go, CNN Medical Analyst Dr. Leana Wen warned Saturday evening.

"We certainly have to acknowledge that we have come a long way, and we're out of the worst of it. We're not going to see the massive surges that we saw over the holidays," said Wen, who is the former health commissioner for Baltimore.

"The problem, though, is that we should really be looking at the numbers for each community instead of looking at the U.S. as a whole because while the U.S. as a whole is doing so much better, and there are pockets of the country that have very high vaccination rates, we also have pockets of the country that are actually undergoing massive surges right now where their hospitals are getting full again," Wen said.

While health experts agree full vaccination offers protection against some variants of COVID-19, Wen added that it's unknown whether a variant resistant to vaccines will emerge.

"We just don't know. If it's anything that we've learned during COVID-19, it's how much we need to be humble in the face of this virus," she said.

She noted that it's "certain" new variants will develop, which could make vaccines slightly ineffective, but not entirely.

"This is another reason why those who are unvaccinated should be vaccinated as soon as possible," Wen said.

Vaccination lags continue in some states

As of Saturday, 44.9% of the total U.S. population was fully vaccinated against COVID-19, while 53.2% had received at least one dose.

Fourteen states have fully vaccinated more than half of their population, CDC data shows, and 16 states have accomplished President Joe Biden's goal to vaccinate 70% of adults with at least one dose by July 4.

Nationally, 65.3% of adults have received at least one dose, with the current pace of vaccinations at 1.3 million doses per day, according to CDC data Saturday.

Mississippi, one of the Southern states where vaccination rates are among the lowest in the country, has fully vaccinated 30% of its total population while 33% has received at least one dose, state health data published Friday shows.

Jackson, Mississippi, Mayor Chokwe Antar Lumumba told CNN on Saturday the state is so far behind in vaccinations in part because of "a dynamic of so many individuals who do not have primary health care physicians on a day-to-day basis, and this is another example of how this pandemic is highlighting the disparities in health care."

In Hinds County, where Jackson is located, 40% of the total population is at least partially vaccinated while 36% is fully inoculated, according to state data.

"If we see people who do not have primary health care physicians and we're asking them to get vaccinated, we're asking them to deviate from the norms that they have in every other fashion of their lives," Lumumba added. "People who have not been to the doctor in many years, and in some instances never, and now we're trying to encourage them to ... go get a shot in their arm."

Lumumba noted one way to encourage vaccination is "meeting people where they are," whether that's in barbershops or churches. He noted that vaccine accessibility and historical mistrust within Black and brown communities are contributing factors to the low vaccination rate in his city, whose population is about 85% Black.

Variants on the rise

Alabama, Louisiana, Arkansas, Tennessee and Wyoming join Mississippi in being among the states with the lowest vaccination rates. That's a problem because experts have been warning that emerging variants could cause serious illness for the unvaccinated.

The CDC has predicted the Delta variant, which was first identified in India, could become the dominant strain in the US.

The Delta variant, along with the Gamma or P.1 variant, have been deemed variants of concern by the CDC—meaning their danger comes from their ability to transmit more easily or cause more severe disease.

The Gamma variant, first identified in Brazil, has been detected in every U.S. state where the CDC has variant information.

Vaccination has been shown as the best way for the U.S. to get ahead of the variants. A recent study by Public Health England found that two doses of a coronavirus vaccine are "highly effective against hospitalization" caused by the Delta variant. The study found the Pfizer/BioNTech vaccine is 96% effective against hospitalization after two doses.

Surgeon General Vivek Murthy previously told CNN there isn't enough data to indicate the effectiveness of Johnson & Johnson's one-dose vaccine in regard to the Delta variant, but it has shown it can help prevent hospitalizations and deaths when people are infected with other strains.

"The key is get vaccinated, get both doses," Murthy said.

Steve Edwards, the CEO of CoxHealth, a system of hospitals and clinics based in Missouri, told CNN on Friday that the Delta variant is unlike others.

"We can't tell why one patient is doing poorly and one is doing well. There's just something different about how this variant is affecting the immune system of our patients," Edwards said.

He added along with low vaccination rates in Missouri, the Delta variant is playing a big role in the surge of cases at his hospitals.

"I think the Delta variant is what's fueling this," he said. "Much of the South, Midwest, much of the places that have low vaccination rates — if confronted with the Delta variant, will see a similar kind of surge of patients as we're beginning to see right now."

The coronavirus variant that first originated in the United Kingdom is now the dominant variant in the United States.

The B.1.1.7 variant of SARS-CoV-2 is present in all 50 U.S. states and is contributing to the surges of coronavirus infection, according to the Centers for Disease Control and Prevention. Not only does it appear to be more transmissible; some research also suggests it can cause more severe disease, which puts more people at risk for hospitalization and death.

What should people do to protect themselves against this more contagious variant? We asked CNN Medical Analyst Dr. Leana Wen, an emergency physician and visiting professor of health policy and management at the George Washington University Milken Institute School of Public Health. She's also the author of the forthcoming book "Lifelines: A Doctor's Journey in the Fight for Public Health."

CNN: What should we do differently now that the B.1.1.7 variant has become dominant in the United States?

Dr. Leana Wen: The B.1.1.7 variant is more transmissible than the previous strains, which means we need to be even more cautious. Some activities that we previously thought were low risk — such as going to the grocery store and taking public transportation — now have a higher risk for virus transmission. Those that were high risk before — such as going to indoor bars or gathering in large crowds — are now even higher risk.

We need to be even more on guard than before. For example, if you are going to eat outdoors at a restaurant, check to make sure that they are abiding by CDC guidelines and there is at least 6 feet of distancing between tables. Those not yet fully vaccinated should wait until they are vaccinated before dining in close proximity with someone else at their table.

That said, this variant is spread just like other variants. The same measures we used before to prevent coronavirus spread are still effective now. That means wearing a mask in public, practicing physical distancing and avoiding indoor gatherings with people not in your household.

It's even more critical than ever to be vaccinated as soon as it's your turn.

CNN: Do the vaccines work against this variant?

Wen: Yes — and this is a really important point. All currently authorized vaccines provide a good level of protection against B.1.1.7 (remember that no vaccine is 100% effective, but getting vaccinated against COVID-19 means that you are at far less risk for contracting the illness and becoming severely ill from it). There are other variants against which the vaccines may be a little bit less effective. However, vaccines are still the critical tool to prevent these other variants, too, and still other variants that may develop in the future.

Viruses mutate when they replicate. The best way to prevent viruses from mutating is to stop the spread. We help slow down and stop the spread when we get vaccinated.

CNN: What about this variant makes it particularly dangerous for young people?

Wen: In recent weeks, we are seeing that younger people are being infected in higher proportions. This includes teens as well people in their 20s, 30s and 40s. This likely is due to a combination of factors.

Older people are those who were vaccinated first and are more protected. Many younger people are not yet vaccinated, and given their increased level of activity, when there is a more contagious variant, they are likely to be infected more. There may also be something about B.1.1.7 that makes it more easily attach to the respiratory system and for people to harbor more virus, thus possibly sickening them more and making them more infectious to others, too.

All this suggests that it's not so much that the virus is somehow attacking younger people preferentially, but younger people are more vulnerable since many have not been vaccinated.

CNN: What should we do to avoid getting infected by this more transmissible variant?

Wen: For people who are not vaccinated, they should try to be vaccinated as soon as possible. That's the best defense against this variant — and others.

Until they can be vaccinated, they should double down on all the precautions. Again, that means wearing a mask in all public places. Studies have shown that it helps to wear two masks — a well-fitting cloth mask on top of a surgical mask. I'd wear two masks like this or an N95 mask in higher-risk settings, such as if you're using public transportation or attending an indoor church service with a lot of people around you.

Try to avoid the most high-risk settings where people don't have their masks on, such as indoor dining. Socialize outdoors only, with members of different households separated at least 6 feet apart.

CNN: The CDC has specifically singled out youth sports as a driver of infections. Should these stop?

Wen: It is true that in Michigan and Minnesota, among other places, there have been outbreaks associated with youth sports. With this more transmissible B.1.1.7 variant, and the fact that youth under 16 cannot yet be vaccinated, it is best to use caution.

Sports that can be played outdoors will be a lot safer than those played indoors. Contact sports like wrestling will be much higher risk than, say, soccer or lacrosse. Players should be wearing masks at all times when physical distancing can't be maintained. Regular surveillance testing of all players can help — for example, if everyone is tested twice a week to check for asymptomatic infection.

It's very important for parents to monitor informal settings just as much as formal settings. You wouldn't want all the precautions to be followed during organized sports, only to have transmission happen at the pizza party after the game. Or for the student-athletes to be letting down their guard and transmitting the virus in the locker room if everyone is gathering there, without masks, for long periods of time.

Ideally, these types of social interactions are limited for the time being, with strict precautions followed so as to prevent virus spread and to allow for as much of the actual sport — and in-person school — as possible.

CNN: What about people who are fully vaccinated — do they still have to be as careful?

Wen: The vaccines we have work very well against the B.1.1.7 variant. People who are fully vaccinated should know that they are very well protected against this strain. "Fully vaccinated" means that it's been at least two weeks after someone has received their vaccines.

Nothing is 100%. What people choose to do once fully vaccinated will depend on their values and their choices. After being vaccinated, activities that were once high risk are going to be lower risk, but there will still be some risk. That needs to be weighed against the benefit of these activities.

The CDC says that fully vaccinated people can see one another and that they can visit one other household with unvaccinated family members, as long as the unvaccinated people are not at high risk for severe outcomes from COVID-19 themselves. It's definitely necessary to wear masks in public places, even after being vaccinated, and to reduce time in high-risk settings like indoor crowded places with unvaccinated people.

I've advocated for thinking about a "coronavirus budget" — essentially, knowing that you can't do everything but should choose the things that are of the highest importance to you.

CNN: Even with a different variant, your bottom-line advice is to follow the same protective measures we're already following?

Wen: That's right. We need to keep in mind that the pandemic is not over. There is absolutely hope and hope is here, but we still need to exercise caution, especially because of this more contagious variant.

Please keep masking, physical distancing and avoiding indoor gatherings. Aim to get vaccinated as soon as possible. Getting vaccinated is the key to stopping this virus from continuing to spread and potentially sicken many more people.

CNN —

Video above: Moderna CEO discusses vaccine boosters, COVID-19 varriants

As experts grow concerned about a possible COVID-19 surge in the winter, the U.S. Centers for Disease Control and Prevention may roll out seasonal vaccine boosters.

"We want to hope for the best, and prepare for the worst," CDC director Dr. Rochelle Walensky told actress Jennifer Garner in an interview streamed on Instagram.

More than a third of the U.S. is fully vaccinated against coronavirus, but it's still short of the benchmark of 70% to 85% of the total population that needs to be immune -- through vaccination or previous infection -- to control its spread.

And many yet to receive the vaccine are those who have not decided whether they want it or have decided against it.

Meanwhile variants have been spreading, threatening to mutate to a point where current vaccines may not offer enough protection against them, experts warn.

Researchers at the CDC are looking into whether a booster specific to variants that are already in the U.S. will be needed as well as if protection from the virus fades over time, Walensky said.

"We are doing the studies on boosters to see if we will need them, and that is six months, one year, two years -- we don't really know," Walensky said. "But we want to be prepared for them should we need them."

If the U.S. does need them, officials have processes already in place to get them out.

"The vision would be that we would do it in the same way that we do flu vaccine," she said. "We hope we don't have to do it every season, but we're preparing in case we do."

Conflict over asking about vaccination status

Health experts have hailed vaccination as the ticket back to a sense of normalcy, but officials have come up against conflicts over who can monitor vaccination decisions.

Wyoming is the latest state to prohibit state agencies from asking people whether they have been vaccinated against COVID-19.

Under a directive signed Friday by Gov. Mark Gordon, the state boards and agencies are ordered to "provide full access to state spaces and state services, regardless of a constituent's COVID-19 vaccination status."

"Vaccine passport programs have the potential to politicize a decision that should not be politicized," Gordon said in a written statement. The press release notes that the governor has been vaccinated and encourages the residents of his state to voluntarily be vaccinated.

Unlike a similar order signed by the governor of Florida, the Wyoming directive is only mandatory for the state government.

However, it says local governments and private businesses "are encouraged" to follow Gordon's directive.

Florida's law prohibits businesses from asking whether employees or customers have been vaccinated.

The CEO of Norwegian Cruise Line Holdings Ltd. said Thursday it could cause the company to suspend Florida departures and move its ships elsewhere.

"At the end of the day, cruise ships have motors, propellers and rudders, and God forbid we can't operate in the state of Florida for whatever reason, then there are other states that we do operate from, and we can operate from the Caribbean for a ship that otherwise would have gone to Florida," CEO Frank Del Rio said during the company's quarterly earnings call.

"In Florida, your personal choice regarding vaccinations will be protected and no business or government entity will be able to deny you services based on your decision," Gov. Ron DeSantis said.

Expanding vaccine authorization

Meanwhile, vaccine manufacturers are preparing for the long haul.

Pfizer/BioNTech, whose vaccine currently has an emergency use authorization, announced the initiation of its application to the U.S. Food and Drug Administration for full FDA approval for people ages 16 and older.

This would be the first COVID-19 vaccine to be assessed for full approval from the FDA.

"We are proud of the tremendous progress we've made since December in delivering vaccines to millions of Americans, in collaboration with the U.S. Government," Albert Bourla, chairman and chief executive officer of Pfizer, said in a statement. "We look forward to working with the FDA to complete this rolling submission and support their review, with the goal of securing full regulatory approval of the vaccine in the coming months."

The FDA is already poised to authorize the company's vaccine in children and teens ages 12 to 15 by early next week, a federal government official told CNN.

The vaccine also has been undergoing a safety and efficacy study in children ages 6 months to 11 years, and the company said it expects to submit for FDA emergency use authorization for children ages 2 to 11 in September.

CDC warns of airborne risk

On Friday, the CDC updated it explanations on how coronavirus is transmitted to stress that inhalation is the main way the virus is spread and placing less emphasis on the risk of picking it up from surfaces.

"COVID-19 spreads when an infected person breathes out droplets and very small particles that contain the virus. These droplets and particles can be breathed in by other people or land on their eyes, noses, or mouth. In some circumstances, they may contaminate surfaces they touch. People who are closer than 6 feet from the infected person are most likely to get infected," the agency says on its updated website. The CDC also updated its scientific brief on how the virus spreads.

"This is not new guidance. This is the beginning of how, perhaps, guidance will begin to evolve," Dr. John Brooks, chief medical officer for the CDC's COVID-19 response, told CNN.

It doesn't change what people need to do, but might help the public better understand how the virus spreads, Brooks said.

The guidance remains the same -- wear a mask when near other people or inside and sharing air with others, keep a distance from others when possible and wash hands frequently.