Pope Francis said getting the coronavirus vaccine was "an act of love" Wednesday, as the head of the world's 1.2 billion Catholics joined a campaign to boost confidence in Covid-19 jabs.

"Thanks to God and to the work of many, we now have vaccines to protect us from COVID-19," Francis said in a message for the US-based "It's Up to You" initiative.

"They grant us the hope of ending the pandemic, but only if they are available to all and if we work together," he said in the video, aimed at communities disproportionately affected by the virus in North, Central and South America.

"Being vaccinated... is an act of love," the 84-year old said.

"And contributing to ensure the majority of people are vaccinated is an act of love. Love for oneself, love for one’s family and friends, love for all people".

Coronavirus has killed at least 4,370,427 people since the outbreak emerged in China in December 2019, according to an AFP compilation of official data.

Despite mass vaccine campaigns, conspiracy theories and distrust of governments or pharmaceuticals are fuelling transmission of the virus.

In the US, the worst-affected country in terms of Covid-19 deaths, the vast majority of new fatalities and serious cases are among the unvaccinated.

Francis was joined by cardinals and archbishops from Brazil, El Salvador, Honduras, Mexico and Peru for the campaign by the Ad Council and COVID Collaborative and the Vatican's Dicastery for Integral Human Development.