Billionaire investor Bill Ackman called the US rollout of the COVID-19 vaccines a "failure of logistics and mismanagement during the transition" in tweets on Tuesday.

There was no logistical excuse for botching the vaccinations, Ackman, CEO of the hedge fund Pershing Square, wrote in a follow-up tweet.

"If Elon Musk can deliver 500k Teslas and Jeff Bezos can provide same-hour delivery, we can vaccinate every American. The time is now!" he tweeted, referring to the CEOs of Tesla and Amazon.

Moreover, Ackman also commented that the mismanagement of the vaccine "seems like genocide" of the elderly.

"We are killing the Greatest Generation ... If the virus killed mostly children rather than the aged, would we sit back and allow this to happen?" he wrote, referring to ageism.

US COVID-19 deaths surpassed 360,000 on Wednesday, according to the Center for Systems Science and Engineering at Johns Hopkins University.

As of Monday, fewer than five million people in the US had been vaccinated.

Ackman's Pershing Square fund posted a 70 percent return last year, much of which was realized from the firm's anticipation of the virus's devastating effects on business early in the year through credit-default swaps, according to Business Insider.