The 75-year-old was speaking on the final leg of his History Tour of Florida and Texas, alongside former Fox News presenter Bill O'Reilly.
Addressing a crowd of mostly unmasked supporters at the American Airlines Centre in Dallas, Texas, Mr Trump described the Covid vaccine as lifesaving.
"Look, we did something that was historic, we saved tens of millions of lives worldwide when we, together, all of us, we got a vaccine done," he said.
“This was going to ravage the country far beyond what it is right now, take credit for it... it’s great, what we’ve done is historic. Don’t let them take it away", he added.
The 45th President of the United States also told supporters they "shouldn't be forced" to get vaccinated if they don't want to.
The jeers came after political commentator Bill O'Reilly told the crowd "both the president and I are vaxxed."
Some Trump supporters booed when the former president revealed he had received his third Covid jab
When the pair then confirmed they had both had their third dose of the Covid vaccine, some in the crowd started booing.
The Republican then urged his supporters to quiet down, and dismissed the booing as coming from a small section of the crowd.
"Don’t, don’t, don’t... that’s alright, it’s a very tiny group up there", he said.
Mr Trump was booed earlier this year when he told supporters he had received the Pfizer vaccine.
At a rally in Alabama in August, the former president told fans the jab was working.
"I recommend taking the vaccine, I did it, it's good... you've got your freedoms but I happened to take the vaccine. If it doesn't work, you'll be the first to know."
Mr Trump - who is from New York - spent the weekend in hospital after testing positive for Covid in October 2020, a month before losing the presidential election to Joe Biden.