The White House on Tuesday announced that the Biden administration plans to purchase an extra 200 million doses of the United States' currently authorized Covid-19 vaccines, which Biden says would give the country enough doses to fully vaccinate 300 million Americans by the end of this summer.

Related: The U.S. Covid-19 vaccination scenario planning guide

Biden aims to increase America's Covid-19 vaccine supply

The announcement comes as the administration looks to accelerate the United States' slower-than-expected rollout of America's two authorized, two-dose Covid-19 vaccines, which are manufactured by Pfizer and BioNTech, as well as Moderna. CDC data shows that, as of Tuesday morning, the federal government had distributed about 41.4 million doses of those vaccines, and about 23.5 million doses had been administered to Americans. Of those, about 20 million Americans had received "one or more doses," according to the data, and about 3.5 million had received both doses of the vaccines.

For weeks, President Biden and his advisers have raised concerns about the country's current limited supply of the vaccines, saying the supply limitations would be one of the biggest obstacles to quickly vaccinating a large share of Americans against Covid-19. To address that issue, the White House on Tuesday said the Biden administration is working on agreements with Pfizer and Moderna to purchase an additional 100 million doses of each of the companies' authorized Covid-19 vaccines.

According to a White House fact sheet, those additional 200 million doses will increase America's total vaccine order by 50%, from 400 million doses to 600 million doses. The administration expects to receive the additional doses this summer, which would ensure the United States has "enough vaccine to fully vaccinate 300 million Americans by the end of this summer," the White House said.

In addition, the White House said the Biden administration for the next three weeks will increase by 16% the number of weekly vaccine doses the federal government ships to states, tribes, and territories. That will increase the weekly minimum supply level shipped to states from a total of 8.6 million doses to 10 million doses for at least the next three weeks, according to the fact sheet. The White House said, "This increase of 1.4 million doses per week will allow millions more Americans to get vaccinated sooner than previously anticipated."

Further, Biden said his administration will begin giving states three weeks' notice of how many vaccine doses they will receive, instead of the one-week notices states received under former President Donald Trump' administration. According to Inside Health Policy, state and local officials have called for earlier and more information about their impending vaccine allocations.

"Until now we've had to guess how much vaccine to expect for the next week, and that's what the governors had to do: 'How much am I getting next week?'" Biden said, adding, "This is unacceptable. Lives are at stake here."

Will the extra doses accelerate America's vaccine rollout?

Many observers applauded the Biden administration's decision to secure more vaccine doses and ramp up distribution to states, though some noted that, at least in the short-term, demand for the vaccines likely will continue to outpace supply.

"Every governor in America faces the same obstacle: The extremely limited supply of vaccines produced and allocated is only a tiny fraction of what our citizens desperately need," Maryland Gov. Larry Hogan (R) said in a statement. "We appreciate the administration stating that it will provide states with slightly higher allocations for the next few weeks, but we are going to need much more supply."

In addition, some observers questioned whether the Biden administration's moves will actually increase America's anticipated vaccine supply, because officials already had expected the country's vaccine supply would increase over time as manufacturing of the vaccines ramped up, under agreements forged by the Trump's administration. According to STAT News, it's unclear whether the Biden administration started new negotiations with the drugmakers to buy the extra doses or if the administration simply is purchasing doses already agreed to under arrangements made by the Trump administration, which allowed the federal government to purchase up to 400 million additional doses from Pfizer and 300 million additional doses from Moderna.

However, observers said the country's vaccine supply may still be larger than expected in the summer if FDA in the coming months issues emergency use authorizations (EUAs) for other promising Covid-19 vaccine candidates, such as Johnson & Johnson's (J&J) experimental single-dose Covid-19 vaccine. On Tuesday, J&J said it expects to release by early next week positive results from a 45,000-person clinical trial on its single-dose Covid-19 vaccine candidate. If FDA ultimately grants an EUA for the experimental vaccine's use in the United States, J&J could deliver 100 million vaccine doses for distribution in the United States by the end of June, the drugmaker said.

America continues to grapple with high rates of new coronavirus cases, hospitalizations, and deaths

The vaccine news comes as America continues to report persistently high rates of new coronavirus cases, hospitalizations, and deaths—and as the country races to vaccinate as many Americans as possible in light of new coronavirus variants that appear to be more transmissible than the original novel virus.

According to data compiled by the New York Times, U.S. officials on Tuesday reported about 151,616 new cases of the novel coronavirus. As of Wednesday morning, officials had reported a total of about 25.4 million cases of the virus since America's epidemic began—up from about 25.3 million cases reported as of Tuesday morning.

According to the Times, the United States' average daily number of newly reported coronavirus cases over the past week was 167,651—which is down by 33% when compared with the average from two weeks ago, when the United States was seeing its worst peak yet in newly reported cases.

As of Wednesday morning, data from the Times showed that the rates of newly reported coronavirus cases were "staying high" in five states that have had a daily average of at least 15 newly reported cases per 100,000 people over the past week. Those states are Maine, New Hampshire, North Dakota, South Carolina, and Virginia.

The Times' data also showed that, as of Wednesday morning, the daily average of newly reported cases over the past seven days was "going down" in Puerto Rico; Washington D.C.; and the remaining 44 states (except Hawaii), which all had been seeing comparatively higher rates of coronavirus transmission.

In Guam, Hawaii, and the U.S. Virgin Islands, meanwhile, rates of newly reported coronavirus cases were "staying low" as of Wednesday morning, the Times' data shows.

U.S. hospitalizations for Covid-19, the disease caused by the novel coronavirus, remained high as of Tuesday, though the number of Americans hospitalized with Covid-19 has decreased significantly from the high of more than 132,400 hospitalizations reported earlier this month. According to data from The Atlantic's COVID Tracking Project, there were 108,957 Americans with Covid-19 hospitalized for treatment on Tuesday, including 20,573 who were receiving care in an ICU and 6,832 who were on a ventilator.

According to data from the Times, U.S. officials also reported about 4,205 new deaths linked to the novel coronavirus on Tuesday. As of Wednesday morning, officials had reported a total of about 425,208 U.S. deaths linked to the virus since the country's epidemic began, up from about 421,003 deaths reported as of Tuesday morning.

(Florko, STAT News, 1/26; Gay Stolberg et. al, New York Times, 1/27; Wang, Inside Health Policy, 1/26 [subscription required]; Rummler, Axios, 1/26; Loftus/Grossman, Wall Street Journal, 1/26; White House fact sheet, 1/26; New York Times, 1/27; "The COVID Tracking Project," The Atlantic, accessed 1/27; CDC data, updated 1/26).