A campaign fronted by doctors and celebrities to persuade European governments, including the UK, to vaccinate all young girls against cervical cancer is being entirely funded by the drug company that markets the vaccine.

Sanofi Pasteur MSD, which markets Gardasil in Europe on behalf of the drug giant Merck, spent millions on what was billed as the "first global summit against cervical cancer", held in Paris on Thursday with doctors and patient organisations from across Europe.

The revelation comes as public health experts express disquiet about the promotion of a vaccine that is only effective in young girls - possibly at the expense of screening programmes that are essential to protect adults. They also worry that the long-term effects of the vaccine are not known. The vaccine protects against the most common strains of the sexually-transmitted human papilloma virus (HPV) which causes cervical cancer.

Diane Harper, a professor at Dartmouth medical school in New Hampshire, who led two vaccine trials, said the vaccine would not protect against all strains of the virus, and that nobody knows whether vaccinated 10-year-old girls would still be protected in 10 years' time, when they are sexually active and at risk. Mass vaccination programmes, she said, would be "a great big public health experiment".

The Paris summit was believed to be the brainchild of Professor David Khayat, a Paris-based specialist in cancer treatment - not vaccines - who has in the past declared consultancy and lecture fees from Merck. The organisers were named as the Club Européen de la Santé, an institution that promotes public health, but its president, Dominique Dupont, told the Guardian she agreed to participate only on condition that Sanofi Pasteur paid.

Celebrities, doctors and journalists were shipped in from across Europe and the United States by PR agencies working for Sanofi. The summit, which resembled a political rally, called for country-wide vaccination programmes.