Nuns danced in conga lines. Teenagers bounced up and down to the rhythm of bongo drums​. And thousands sang ​along as singers and bands alternated sets on the huge stage built just last month in a Roman suburb for a youth festival that has become known as the Catholic Woodstock.​

“This is the youth of the pope!” many chanted.

Christina Mertens, who works for the Roman Catholic Diocese of Orange County, in California, was among the hundreds of thousands of people who converged on Rome over the past week for the six-day event, which ends on Sunday.

Back home, she said, she didn’t see many young adults at church, “I think a lot people are busy with other priorities,” she said. But on Saturday, at the concert, she felt invigorated. “Being here I was realizing, wow, this is exactly what we need to see for the church.”

World Youth Day, as it is known, is held every two or three years in various locations around the world. This year, it coincided with the Roman Catholic Jubilee — a holy year that usually takes place every 25 years — and kicked off with a gathering of hundreds of mostly young Catholics from 70 countries who promote their faith online.

That reflects the Vatican’s growing recognition of the importance of Catholic social media influencers in its efforts to engage more young people.

“It was right that the Church recognized this new type of evangelization and supported it” in an official manner, said Nicola Campo, 19, a popular Italian TikTok influencer. He attended the two-day Jubilee of Digital Missionaries and Catholic Influencers, and on Friday, met with Cardinal Pietro Parolin, the Vatican’s secretary of state.

The week’s events also included an opening Mass at St. Peter’s Square, confession stations set up at the Circus Maximus, and other concerts and seminars as well as prayers in churches and basilicas.

St. John Paul II created World Youth Day in 1985 to tap into what he saw as a reservoir of authentic faith among young people. Some four million youths participated in the event in Manila in 1995, which is still a record. During the 2000 celebration, also held in Rome, two million people attended. This year the turnout was expected to be about 500,000.

The reason for the drop in attendance this year is not clear. But studies by universities, think-tanks and research centers show that, especially in the West, many young people, even if they identify as spiritual, express skepticism of traditional religious institutions. Studies also show that there has been an increase in people with no religious affiliation at all.

“We see that young people are searching for something spiritual,” said the Reverend José María Díaz-Dorronsoro, of the Pontificia Università della Santa Croce in Rome. But, he added, “this doesn’t mean that they are turning to a traditional religion” or going to Mass. The university is one of seven that participated in a study of young people’s attitudes toward faith and religion, presented at a seminar in Rome last month.

He noted many possible reasons, including disagreement with some of the church’s stance on moral issues, including contraception, acceptance of gay marriage and abortion, as surveys of young Christians in the United States show. There is also frayed trust caused by the clerical abuse scandal, he said.

At the same time, there is a risk of growing “religious illiteracy” within the family, said Rita Bichi, a sociologist at the University Cattolica del Sacro Cuore who studies youth participation in religion.

The reason, she said, is that some women, who traditionally transmit the faith in their families, have been leaving the church in part because they feel excluded. The need to better include women in decision-making positions in the church has repeatedly emerged as a priority of Catholics worldwide.

For many young people, being Catholic is difficult in today’s world with all its distractions, especially going to Mass and participating in the Church, said Andres Maria Rodriguez, 20, a first-year engineering student from Chiapas, Mexico, who attended the festival. He said being there was a jolt of positive energy. “It’s been insane, a once in a lifetime experience,” he said.

The Church has long been trying to expand its appeal to young people; for years the Vatican has run an account for the pope on social media. In September, the Vatican will canonize the first millennial saint, Carlo Acutis, who died of leukemia in 2006 at age 15. He had created a website on eucharistic miracles, and his youth and deep faith spread his appeal among young Catholics after his death. Some call him “God’s influencer.”

Thousands of young people this week thronged to a church in downtown Rome to pray before a relic of Acutis.

Katie Prejean McGrady, who hosts a show on Sirius FM, was one of several hundred Catholics who participated in the gathering of digital influencers.

“It was a joyous celebration of this group of people doing this particular kind of work,” she said. And then the church saying, “we’re supporting you in this,” she said.

Brett Robinson a professor who studies the digital world from the University of Notre Dame, also attended. He said outreach online was “a very effective route to evangelization.” But he and others also discussed what they consider the dangers of using a medium that focuses on personalities who often turn into brands.

But those concerns did not dampen the enthusiasm of those attending Saturday’s concert.

In a moment when “it’s so easy to feel like faith is dying,” said Vanessa Garlepp, 24, a biomedical engineer, from Orange County, California, “it’s really beautiful to see just the unity and the energy of the young church. It gives a lot of hope.”