(Photo : Graeme Jennings- Pool/Getty Images)
Anthony Fauci, director of National Institute of Allergy and Infectious Diseases at NIH, looks on before testifying at a Senate Health, Education, and Labor and Pensions Committee on Capitol Hill, on September 23, 2020 in Washington, DC.

Dr. Anthony Fauci said Monday the U.S. could reach "herd immunity" by late spring or early summer next year as a COVID-19 vaccine starts rollout.

Fauci-director of the National Institute of Allergy and Infectious Diseases-made his assumptions based on a scenario where the general population will get vaccinated by late March, paving the way for herd immunity.

"The real bottom line is when do you get the overwhelming majority of the population vaccinated so that you can get that umbrella of herd immunity?" Fauci told MSNBC's Hallie Jackson.

He added that herd immunity will still depend on the "efficiency of the rollout" of vaccines, reported NBC News.

He predicted that Americans without underlying condition could get inoculated by the end of March or the beginning of April.

Previously, Fauci said 75 to 80 percent of the country's population would need to be vaccinated before the U.S. could reach herd immunity in summer, noted New York Post.

But with vaccine deliveries underway, Fauci said immunity would start being a large-scale

However, with the first rounds of COVID-19 vaccine deliveries now underway, Fauci said the U.S. could realize large-scale, indirect immunity several months earlier, said a report from Newsweek.

Related Story: First COVID-19 Vaccine Shipments Reach Distribution Sites, Inoculations to Start Monday

Pfizer's COVID-19 vaccine, now approved by the Food and Drug Administration, began shipping out Sunday. The first patient in the nation to receive the shot was a critical care nurse in New York City.

Fauci Predicts Normalcy by Fall

With the help of widespread vaccination, Fauci hoped life could start going back to normal by fall.

He said there will be some "degree of relief" by that time where infection will be slow.

He reminded that public health measures such as mask usage, event cancellations and enhanced hygiene protocols are still likely going to continue "until the second half and beyond of 2021."

For the public health measures to be pulled back, he said the best indicator is if the level of infection in society is "so low that it's no longer a public health threat."

Fauci to Get Publicly Inoculated

As a form of encouragement to the public, Fauci said he'd be willing to be vaccinated publicly as soon as possible.

He assured that if his turn to get inoculated comes up, which he said will be "very soon", he'll do it publicly "so that people can see that I feel strongly that this is something we should do."

Read also: Depression Among Children Skyrocket Under COVID-19 Lockdown, Study Says

Even with a vaccine on the ready, Fauci urged Americans not to let their guard down and continue meeting public health measures, reported US News & World Report.

He reminded the public that a vaccine is not a substitute for "the normal standard public health measures" that people have been encouraged to meet since the start of the pandemic.

"It's not a substitute. It complements it," Fauci said.

His predictions come as the coronavirus death toll in the country surpassed 300,000 and broke record daily death tolls with the highest reported at over 3,300 on December 11, according to data from Johns Hopkins University.