COVID-19 vaccines are set to begin in the U.S. as deaths approach the 300,000 mark. The head of the government's vaccine drive said as much as 80% of the population might be inoculated by summer.

Thousands of vials of the vaccine are set to arrive in 50 U.S. states Monday, as top health experts express optimism that front-line health care workers can start giving the shots soon, CNN reported.

Good vehicles carrying suitcase-sized containers of vaccines departed Pfizer's manufacturing facility in Kalamazoo, Michigan late Sunday  kicking off the biggest and most extensive vaccine distribution.

The Centers for Disease Control and Prevention signed off on U.S. immunizations against the virus to begin as early as Monday - saying the objective is to help "restore some normalcy to our lives and our country."

The U.S. hopes to vaccinate around 100 million people by the end of March, Operation Warp Speed chief adviser Dr. Moncef Slaoui told Fox News in an interview Sunday.

Slaoui said the U.S. expects to have around 40 million doses of vaccine allocated by the end of this month - which would include the just approved treatments from Pfizer. One from Moderna is expected to be authorized for emergency use in the coming days, Reuters reported.

Another 400 boxes containing around 390,000 vials were expected to arrive Tuesday. Pfizer said there were five doses of vaccine per vial.

As the virus continues to spread across much of the U.S., health officials said as much as 80% of the country's population could be immunized by next summer, putting the so-called "herd immunity" within reach.

Meanwhile, a $908 billion bipartisan pandemic relief plan expected to be introduced in the U.S. House of Representatives as early as Monday will be divided into two tranches in an attempt to gain Congressional authorization, a source with knowledge of the matter disclosed.

For months, House legislators have been trying to reach an accord on a new COVID stimulus measure, after Congress gave the green light for a $3 trillion relief package earlier this year.