Washington DC - More than 50% of American adults and 40% of the total US population are now fully vaccinated against Covid-19, according to the Centers for Disease Control and Prevention (CDC).

A total of 135 million people above 18 have received both doses of the coronavirus vaccine and are fully vaccinated as of Tuesday, the federal health agency's latest data shows.

It comes to 51.7% of the US adult population.

Meanwhile, 62.8% of the country's adults, or 168 million, have received one dose.

The CDC tally includes two-dose vaccines from Moderna and Pfizer/BioNTech, as well as Johnson & Johnson's one-shot vaccine.

The numbers are on track to reach President Joe Biden's goal of 70% of Americans to have gotten at least one jab by July 4.

Vermont continues to lead the nation in vaccinations. As per the latest numbers, "We're at 78.4% of the eligible population, just 8,708 away from our 80% goal, when remaining restrictions are lifted," the state's Governor Phil Scott said on Twitter.

"If 2,000 Vermonters get vaccinated a day, we will reopen on June 6," he tweeted.

Meanwhile, Dr. Melvin Sanicas, a vaccinologist and public health expert, said on Tuesday that immunity from natural coronavirus infection starts to decline after six to eight months, but that fully vaccinated people will still have good immunity after more than a year and most probably longer.

"Those who have been infected benefit from vaccination - it gives them a boost – strong, lasting immunity," he added in a tweet he posted on the CDC Twitter page.

However, some variants of the virus have continued to spread among those who are still not vaccinated.

The Springfield-Greene County Health Department has reported rising cases among unvaccinated residents. The Department confirmed cases of infection with the Indian variant B16172 in Springfield, Missouri.

"This is a more highly infectious variant, and early research indicates that the natural immunity resulting from having Covid-19 may be ineffective against this variant," the Health Department said in a press release.

On Tuesday, 12,976 new coronavirus cases were reported in the US, taking the national total to 34,136,738.

On the same day, 287 new deaths were reported in the country. With this, the Covid-19 death toll in the US increased to 610,436.

A total of 27,940,918 Americans have so far recovered from coronavirus infection, according to the latest data from Johns Hopkins University.

Amidst reopening strategies and dropping restrictions, the CDC has granted long-awaited approval to some cruise lines to resume operations from Florida ports as a step toward reinstating regular passenger service at the end of June.