Here’s a subject for a PhD thesis: religion interpreted through the genre of the musical. There’s already a fair bit to study: The Sound of Music, Godspell, Jesus Christ Superstar, Joseph and the Amazing Technicolor Dreamcoat. If you want some fun, add in Sister Act.

Now there’s a new musical that would require a chapter of its own in that doctoral thesis about religious visions. And if Bernadette de Lourdes takes off, it won’t just be filling theatre seats but could draw more visitors, restoring the economic fortunes of the French pilgrimage centre.

Created by the producer Roberto Ciurleo, whose previous work was about Robin Hood, it has just opened in Lourdes and tells the story of the town’s most famous daughter: Bernadette Soubirous, who in 1858 saw a series of 18 apparitions of the Virgin Mary.

When religious musicals work, they explore the magnetism of the lead character and conflicts to be faced. Bernadette’s is a gripping tale. She was an ill-educated peasant girl who, despite enormous pressure to recant, stubbornly stuck to her story of the visions of the beautiful lady who had urged her to dig for a spring – the lady was the Virgin Mary, and the spring became the healing waters of the grotto of Lourdes. It still attracts pilgrims: this week, in which the feast of the assumption of Mary is celebrated, will see a surge in numbers. But there aren’t enough year-round visitors any more. And as their numbers have declined, so have the fortunes of hotels, restaurants and souvenir shops. Even the main basilica has suffered: donations have been falling for nearly a decade.

This might be due to a decline in Christianity, or to Lourdes becoming as much a shrine to tat as to the Virgin Mary. It’s certainly put me off. All those souvenir shops selling tourist kitsch, from plastic Virgin Marys filled with water from the grotto, to plaster statues, rosary beads and prayer cards. Even Pope Francis has taken action, recently appointing a bishop to try to accentuate the spiritual values of Lourdes again above the financial.

And those values are certainly there – and it’s those that cause me to regret not making a pilgrimage. For at its best Lourdes is an antidote to a Love Island culture where physical perfection, beauty, sexiness, celebrity and material wealth are the top priorities. It’s not the miraculous cures that are said to happen at Lourdes that attract me. The more I hear about it from people who have ventured there and what I’ve read about it, I realise that Lourdes stands for something that is often lacking in everyday life. It is a place where the first are last and the last first.

The true miracle at Lourdes is the way in which sick people take centre stage. Lourdes functions because of the many volunteers who help look after the sick, with their chairs and stretchers, and take them down into the baths to the healing waters. There are specialist medical staff available but the volunteers, many of whom use their annual leave to do this work, ensure that those who are ill or disabled are the top priority. Many of them are young and say the encounter with people with illness and disabilities has changed their approach to life and helped them make friends with people they would otherwise never have met. As one of them said: “Lourdes teaches us that we are all equal in God’s eyes.” It’s rare to have that sense of people’s equal worth endorsed elsewhere. Bodies certainly matter in Lourdes, but so does the soul. In our culture, we pamper the body, whether through food or beauty products, but spirits seem to be withering from neglect; depression and anxiety are rife.

‘Donations have been falling for nearly a decade. This might be due to a decline in Christianity, or it might be due to Lourdes becoming as much a shrine to tat as to the Virgin Mary.’ Photograph: Pascal Pavani/AFP/Getty Images

The new musical is not the first attempt at dramatising what happened to the young peasant girl. The Song of Bernadette, filmed in 1943 and starring Jennifer Jones, was a saccharine effort. But the book it was based on is quite different and that it was written at all is remarkable. Franz Werfel, a German-speaking Jew and his wife, Alma, the widow of the composer Gustav Mahler, were refugees who in 1940 fled first to Paris and then to the Pyrenees. Various Catholic peasant families took it in turns to hide them in their homes. There they were told about Bernadette by people whose grandparents were alive at the time of her visions.

Werfel pledged to write a book about her if he lived. In it he told the story of the young peasant, whose near-destitute family lived in a disused prison cell, and who was to the town’s bourgeoisie the unlikeliest of people to receive a vision of the mother of God. But with integrity and courage she stood by her visions when the town authorities and the church belittled her. Eventually those same sceptics became the cynics who turned Lourdes into a tourist trap as much as a pilgrimage site and, just 26 years after Bernadette’s visions, Emile Zola wrote a blistering denunciation of Lourdes’ commercialism.

Not that Lourdes is unique in combining God and mammon. Tourism in the west owes its origins to Christian pilgrimage, to places such as Canterbury, where Thomas Becket was murdered in the cathedral in 1170, to Assisi and to Santiago de Compostela. These places prospered by offering food, shelter and souvenirs. Yet they all still offer something else: a crossingpoint between the materialism of this world and the yearning of people for a connection with something quite different.

The huge basilica above the shrine at Lourdes is a symbol of the wealth and power of the Catholic church. But it is the grotto and the baths that visitors remember, which represent something much more powerful: a faith that cannot be fully contained by institutions but is expressed through a communal experience that so many people today seek but often do not find.

• Catherine Pepinster is a former editor of the Tablet and author of The Keys and the Kingdom: the British and the Papacy