The United States' effort to begin vaccinating millions of Americans against the novel coronavirus is off to a slower-than-expected and complicated start. And now, faced with cases of a new and more-contagious variant of the virus in the United States and abroad, scientists and public health officials are weighing whether they should implement some largely untested changes to how they're rolling out the vaccines.

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US coronavirus vaccine roll out sees slow and bumpy start

Late last year, FDA issued emergency use authorizations for two vaccines against the novel coronavirus—one made by Pfizer and BioNTech and one made by Moderna—allowing the United States to begin doling out the inoculations. Currently, public health officials and health care providers are working to vaccinate frontline health care workers, as well as staff and residents of long-term care facilities. CDC has recommended that those individuals, who represent nearly 24 million people, should be the first in America to receive authorized vaccines against the novel coronavirus because they are at high risk for contracting the pathogen. CDC hasn't yet released official guidance recommending which Americans should be in the next priority group for receiving an authorized coronavirus vaccine.

Despite the United States' current vaccination effort focusing on a relatively small, targeted group of health care workers and patients, progress has been slower than expected. According to CDC data, the federal government had distributed about 15.4 million doses of the authorized coronavirus vaccines as of Monday morning, and about 4.5 million U.S. residents received their first doses of the two-shot vaccines.

In comparison, the Trump administration last year had said it would distribute at least 20 million doses of the vaccine by 2020's end, the Washington Post reports. Moncef Slaoui—the scientific adviser of Operation Warp Speed, the Trump administration's coronavirus vaccine initiative—on Wednesday acknowledged that the number of Americans who had received their first dose of a coronavirus vaccine so far was "lower than what [the administration] hoped for."

According to the Post, coronavirus vaccine distribution "has been marked by chaos and confusion" in some areas of the country. For instance, the Post reports, "[m]any medical workers who believe they should have priority access are finding that inoculation remains elusive. And most states moved into the third week of immunization not yet beginning to get shots to long-term care facilities, which have been epicenters of infection."

Experts say there are many reasons for the slow and bumpy roll out, including chronic underfunding at public health departments, staffing shortages, a lack of centralized communication and guidance on how to distribute and prioritize vaccine doses, and difficulties coordinating vaccine signups and eligibility. And at the current rate, vaccinating enough Americans to reach heard immunity against the novel coronavirus could "take years," as opposed to the hoped-for timeline of several months, the Post reports.

Faced with more contagious coronavirus variant, officials consider ways to speed up vaccinations

Public health experts say America's lagging coronavirus vaccine rollout is troubling on its own, given the country's persistently high rates of new coronavirus cases, hospitalizations, and deaths. However, experts are particularly worried about the delay because of a newly identified variant of the coronavirus that is more contagious and is circulating in at least 33 countries—including the United States.

So far, public health officials haven't announced any evidence showing that the new coronavirus variant causes more severe cases of or higher mortality from Covid-19, the disease caused by the virus. But evidence suggests the new variant is more infectious, meaning it could worsen America's coronavirus epidemic. As Ashish Jha, a general internist and professor of global health at the Harvard T.H. Chan School of Public Health, and Robert Wachter, chair of the department of medicine at the University of California-San Francisco, wrote in an opinion piece in the Post, "A more infectious virus means more cases, which means more hospitalizations and deaths."

In light of that threat, some scientists and public health officials are weighing largely untested changes to their vaccine distribution plans that are aimed at getting as many people vaccinated—at least partially—as soon as possible.

For example, the New York Times reports that scientists are considering whether it's safe and effective to delay a person's second dose of the authorized coronavirus vaccines, which currently require that patients receive their first and second doses about one month apart. Doing so could allow more Americans to receive at least one dose of a vaccine, which might provide some level of protection against the virus, according to preliminary data from some vaccines' clinical trials. According to the Times, officials in Britain have moved to delay second doses of coronavirus vaccines made by AstraZeneca and Pfizer in an effort to distribute the vaccines more widely and potentially give people partial protection against the virus.

But it's not yet clear how robust that protection could be or how long it could last, experts say. And because of those uncertainties, Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, during a CNN interview on Friday said he "would not be in favor of that" for the United States. "We're going to keep doing what we're doing" in terms of how the United States' authorized coronavirus vaccines are administered, he said.

Separately, Slaoui suggested a different approach for America. During an interview on CBS' "Face the Nation," Slaoui suggested giving people two half-doses of Moderna's coronavirus vaccine. Slaoui said while there's no or little data supporting the efficacy of delaying doses, "injecting half the volume" of a dose of Moderna's vaccine might constitute "a more responsible approach that will be based on facts and data to immunize more people."

But some experts say the United States doesn't need to focus on stretching the number of vaccine doses it has available. Instead, it needs to focus on administering the number of doses it already has to Americans.

"We have an issue with distribution, not the number of doses," Saad Omer, a vaccine expert at Yale University, said. "Doubling the number of doses doesn't double your capacity to give doses," Omer added.

Further, Shweta Bansal, a mathematical biologist at Georgetown University, said delaying doses could decrease the likelihood that Americans would get fully vaccinated against the novel coronavirus. "The longer the duration between doses, the more likely people are to forget to come back. … Or people may not remember which vaccine that they got, and we don't know what a mix and match might do," she said.

For AstraZeneca's part, Menelas Pangalos, EVP of biopharmaceuticals research and development at the company, said when it comes AstraZeneca's vaccine (which hasn't been authorized for use in the United States), extending the time between doses "gives you a lot of flexibility for how you administer your vaccines, dependent on the supply that you have." Pangalos added the delaying people's second doses of the vaccine could help countries to get "in very good shape for immunizing large swaths of their populations to protect them quickly."

Steven Danehy, a spokesperson for Pfizer, was more cautious regarding Pfizer's vaccine. "Although partial protection from the vaccine appears to begin as early as 12 days after the first dose, two doses of the vaccine are required to provide the maximum protection against the disease, a vaccine efficacy of 95%," he said. "There are no data to demonstrate that protection after the first dose is sustained after 21 days," Danehy added.

And Ray Jordan, a spokesperson for Moderna, told the Times that the company could not comment on changing its dosing plans at this time.

FDA pushes back against suggestions to reduce, delay vaccine dosage

In response to proposals to reduce or delay vaccine does, FDA Commissioner Stephen Hahn and Peter Marks, director of FDA's Center for Biologics Evaluation and Research, in a statement released Monday said while the ideas "are all reasonable questions to consider and evaluate in clinical trials," the suggested changes "to the FDA-authorized dosing or schedules of these vaccines is premature and not rooted solidly in the available evidence."

The officials added, "Without appropriate data supporting such changes in vaccine administration, we run a significant risk of placing public health at risk, undermining the historic vaccination efforts to protect the population from Covid-19." They continued, "Using a single dose regimen and/or administering less than the dose studied in the clinical trials without understanding the nature of the depth and duration of protection that it provides is concerning, as there is some indication that the depth of the immune response is associated with the duration of protection provided" (FDA release, 1/4; Owens, "Vitals," Axios, 1/5; Stanley-Becker, Washington Post, 12/30/20; Wu/Robbins, New York Times, 1/4; O'Donnell/Spalding, Reuters, 12/31/20; Caina Calvan/Kunzelman, Associated Press, 12/31/20; Robbins et al., New York Times, 12/31/20; Wachter/Jha, Washington Post, 1/3; New York Times, 1/4).