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Get ready to roll up your sleeve for a COVID-19 shot.

As many as 20 million Americans could be inoculated against the coronavirus before the end of the year — and the number jumps to 80 million by March — if the government hits the target deadlines of the vaccine campaign’s top scientist, Moncef Slaoui.

Slaoui’s schedule put the number of monthly vaccines at 25 million to 30 million a month, starting in January. At that pace, roughly a fourth of the population could be vaccinated before spring, Business Insider reported.

Earlier predictions by two other top government officials, Dr. Anthony Fauci and Health and Human Services Secretary Alex Azar, had set April as the rollout date.

First in line will be healthcare workers and those highest at risk, such as seniors with pre-existing conditions. An advisory panel to the Centers for Disease Control and Prevention will determine the specifics of the allocation plan.

Hitting the target dates is only possible if regulators approve two vaccines in the works by pharmaceutical giants Pfizer and Moderna. Slaoui told reporters that he expected both companies to ask the Food and Drug Administration for emergency use authorization by early December.