NEW YORK (NewsNation Now) — New York state Monday confirmed its first case of the new coronavirus variant in a 60-year old man with no known travel history. The discovery adds a new urgency as the Empire State works to vaccinate its 20 million residents.

That effort is falling behind and fueling a debate governments are having around the globe: Should they be focused on giving one shot or two?

Given a less than speedy vaccine rollout by Operation Warp Speed, some experts suggest delaying the booster and putting a single dose in as many arms as possible to give more Americans at least some level of immunity. Depending on the study, that level looks quite acceptable.

British regulators believe a single shot of the Moderna vaccine is 80 to 90% effective and say the Pfizer/BioNTech shot is 70% effective after one dose and 95% effective after two.

Other experts argue that since it’s a novel virus being attacked with new medications, the data may be incomplete.

“If I was told all of a sudden, ‘You’re gonna get half a dose,’ I would sort of scratch my head and wonder why that changed,” OhioHealth’s Dr. Joseph Gastaldo told NewsNation affiliate WCMH.

On Monday evening, the Food and Drug Administration released a statement on following the authorized dosage and schedule for COVID-19 vaccines:

“Two different mRNA vaccines have now shown remarkable effectiveness of about 95% in preventing COVID-19 infection in adults. As the first round of vaccine recipients become eligible to receive their second dose, we want to remind the public about the importance of receiving COVID-19 vaccines according to how they’ve been authorized by the FDA in order to safely receive the level of protection observed in the large randomized trials supporting their effectiveness.

We have been following the discussions and news reports about reducing the number of doses, extending the length of time between doses, changing the dose (half-dose), or mixing and matching vaccines in order to immunize more people against COVID-19. These are all reasonable questions to consider and evaluate in clinical trials. However, at this time, suggesting changes to the FDA-authorized dosing or schedules of these vaccines is premature and not rooted solidly in the available evidence. 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.

The available data continue to support the use of two specified doses of each authorized vaccine at specified intervals. For the Pfizer-BioNTech COVID-19 vaccine, the interval is 21 days between the first and second dose. And for the Moderna COVID-19 vaccine, the interval is 28 days between the first and second dose.

What we have seen is that the data in the firms’ submissions regarding the first dose is commonly being misinterpreted. In the phase 3 trials, 98% of participants in the Pfizer-BioNTech trial and 92% of participants in the Moderna trial received two doses of the vaccine at either a three- or four-week interval, respectively. Those participants who did not receive two vaccine doses at either a three-or four-week interval were generally only followed for a short period of time, such that we cannot conclude anything definitive about the depth or duration of protection after a single dose of vaccine from the single dose percentages reported by the companies.

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. If people do not truly know how protective a vaccine is, there is the potential for harm because they may assume that they are fully protected when they are not, and accordingly, alter their behavior to take unnecessary risks.

We know that some of these discussions about changing the dosing schedule or dose are based on a belief that changing the dose or dosing schedule can help get more vaccine to the public faster. However, making such changes that are not supported by adequate scientific evidence may ultimately be counterproductive to public health.

We have committed time and time again to make decisions based on data and science. Until vaccine manufacturers have data and science supporting a change, we continue to strongly recommend that health care providers follow the FDA-authorized dosing schedule for each COVID-19 vaccine.

The FDA, an agency within the U.S. Department of Health and Human Services, protects the public health by assuring the safety, effectiveness, and security of human and veterinary drugs, vaccines and other biological products for human use, and medical devices. The agency also is responsible for the safety and security of our nation’s food supply, cosmetics, dietary supplements, products that give off electronic radiation, and for regulating tobacco products.”

NewsNation’s Marni Hughes talks with one of the leading experts on coronavirus vaccines, Dr. Steven Thomas, OF Upstate University Hospital in NEW YORK

At Long Island Jewish Medical Center in Queens, critical care nurse Sandra Lindsay, the first in America to receive the COVID-19 vaccine, is now among the first to be fully-vaccinated; she got her second dose on Monday.

“I know that we’re not out of the woods yet – we don’t have that herd immunity yet but the burden feels definitely much lighter today,” said Sandra Lindsay.

Like major cities around the globe, there is growing concern in New York over the relatively small number of people who’ve received their first dose of the COVID-19 vaccine. Just over 100,000 in a city of 8 million.

The initial rollout has been slow as health care workers familiarize themselves with how to store and administer the shots. The city’s mayor says the time for training is over.

 “Now— from this point on— 7 days a week, 24/7 has to be the attitude and the approach,” said Bill De Blasio.

While the U.K. works to give a single dose to more people, it’s relying to some degree on science that’s not yet complete, a fact that worries the top infectious disease expert in America.

Dr. Anthony Fauci told NBC’s ‘Face the Nation’ on Sunday that the stakes are too high not to stick to the plan.

“Go into the trenches, go into the hospitals, go into the intensive care units and see what is happening. Those are real numbers, real people and real deaths,” said Dr. Fauci.

Over the weekend, New York State surpassed 1 million confirmed coronavirus cases— the fourth state to hit that milestone, according to Johns Hopkins data, after Texas, California and Florida.