All American adults now are eligible to get a Covid-19 vaccine, but some experts are worried that the shift to vaccinating all populations could leave behind some of the nation's most vulnerable residents.

Good? Bad? Ugly? We've updated our take on what's next for the epidemic.

All 50 states expand vaccine eligibility to all adults

In March, President Biden called on all states to make all American adults eligible for Covid-19 vaccines by May 1. However, Biden earlier this month moved up that date by two weeks to April 19.

Now, all 50 states and Washington D.C. have met Biden's deadline for opening vaccine eligibility to all adults. Hawaii, Massachusetts, New Jersey, Rhode Island, and Vermont on Monday were the last states to expand vaccine eligibility to all their residents ages 16 and older, ABC News reports.

"It's truly historic that we have already reached this milestone," said Nandita Mani, the associate medical director of infection prevention and control at the University of Washington Medical Center.

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In addition to expanding vaccine eligibility to all adults, 18 states and Puerto have lifted their residency requirements for vaccine appointments, NBC News reports.

The United States is now administering an average of 3.2 million vaccine doses per day, up from an average of about 2.5 million doses per day a month before, the New York Times reports. According to CDC data, more than 130 million American adults—or 50.7% of the country's total adult population—have received at least one dose of a Covid-19 vaccine. At this pace, the United States is expected to meet Biden's goal of administering 200 million Covid-19 vaccine doses within his first 100 days in office, which will be April 30, and to vaccinate 70% of its population by mid-June, the Times reports.

"We're making tremendous progress, but we're still in the race against this virus, and we need to vaccinate tens of millions more Americans," Biden said on Sunday. "We could have a safe and happy Fourth of July with your family and friends in small groups in your backyard. That's going to take everyone doing their part. Get vaccinated."

What expanded vaccine eligibility may mean for vulnerable American

Even though more than 80% of Americans ages 65 and older have received at least one vaccine dose, millions of older Americans have not yet received a single vaccine dose, Axios' "Vitals" reports. And although some public health officials and experts believe opening vaccine eligibility to all American adults will result in more Americans getting vaccinated more quickly, others are concerned the expanded eligibility will mean the most vulnerable Americans—including those ages 65 and older, who considered to be at risk of a severe case of Covid-19 and death—will have difficulty scheduling their vaccine appointments, the Times reports.

According to experts, there are many reasons why vulnerable Americans who have been eligible for a vaccine may have not yet been vaccinated. For example, Cindy Prins, an epidemiologist at the University of Florida, said, "There may be people who are not necessarily homebound, but maybe they don't drive." She added, "Maybe it's not easy and convenient for them to get somewhere to get vaccinated."

Supply shortages, confusing procedures for scheduling appointments, and vaccine hesitancy are among the other reasons Americans who have been eligible for vaccines may have not yet been vaccinated, the Times reports.

Prins said opening vaccine eligibility to all adults could make it even more challenging for these individuals to get vaccinated, particularly if states and counties shift their resources to mass vaccination sites, which may be intimidating or uncomfortable for people at risk of developing severe cases of Covid-19.

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"I think there are some folks who want to get the vaccine, but they're still very worried about getting exposed to other people," Prins said. "It's a little bit of a strange situation where we're like, 'Stay away from everyone, but please come here to our massive vaccine clinic.'" Prins said some older adults may wait to get vaccinated until their primary care providers can administer the vaccine.

Lisa Cooper, director of the Johns Hopkins Center for Health Equity, suggested that to counter the problem, health officials could encourage younger Americans who have recently become eligible for vaccines to help get the older people in their lives vaccinated. "We need to start asking the younger folks, 'Where's your mom? Your grandmother? Have they all gotten their vaccines yet? If not, we've got several slots and we want your whole family here,'" Cooper said.

Where America's coronavirus epidemic stands

Although the pace of America's vaccine rollout has accelerated, new coronavirus cases and hospitalizations are continuing to rise.

"More people in the United States are being vaccinated every single day at an accelerated pace," CDC Director Rochelle Walensky said during a White House Covid-19 briefing on Monday. "On the other hand, cases and hospitalizations are increasing in some areas of the country and cases among younger people who have not yet been vaccinated are also increasing."

Experts say the recent uptick in coronavirus cases likely stems from states easing coronavirus-related restrictions, the spread of more transmissible coronavirus variants, and pandemic fatigue, the Wall Street Journal reports.

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According to data compiled by the Times, the United States' average daily number of newly reported coronavirus cases over the past week was 67,175—up by 4% compared with the average from two weeks ago.

The Times' data showed that, as of Tuesday morning, the rates of newly reported coronavirus cases were "staying high" in Puerto Rico, Washington, D.C, and 22 states that have reported a daily average of at least 15 newly reported cases per 100,000 people over the past week. Those states are Colorado, Delaware, Florida, Illinois, Indiana, Maine, Maryland, Michigan, Minnesota, New Hampshire, North Carolina, North Dakota, Ohio, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Virginia, Washington, and West Virginia.

In addition, the rate of newly reported coronavirus cases was "going up" as of Tuesday morning in Louisiana, Mississippi, Nevada, and Wisconsin, which have had comparatively lower case rates, the Times reports. In the remaining states and U.S. territories, rates are "going down" or "staying low," according to the Times' analysis.

Meanwhile, data also shows hospitalizations are rising again. According to the Times' data, 44,411 Americans with Covid-19 were hospitalized on Monday—up by 10% compared with the average from two weeks ago.

Even as cases and hospitalizations are increasing, data shows deaths are continuing to decline. According to the Times' data, 483 new deaths were linked to the coronavirus on Monday, down 5% compared with the average two weeks ago.

(Schumaker, ABC News, 4/19; Anthes et al., New York Times, 4/19; Chiwaya, NBC News, 4/19; Ivory/Collins, New York Times, 4/19; Owens, "Vitals," Axios, 4/20; Maxouris, CNN, 4/20; West, Wall Street Journal, 4/19; New York Times, 4/20).