UPDATE 1-Pfizer partner BioNTech sees no role for its vaccine in UK challenge trial

(Adds comments by further companies, WHO)

FRANKFURT, Sept 24 (Reuters) - Pfizer’s German development partner BioNTech on Thursday joined other leading COVID-19 vaccine developers in ruling out participation in British plans to test experimental inoculations by deliberately infecting trial volunteers.

“BioNTech’s vaccine candidate is not part of this study,” a spokeswoman said.

Britain is planning to host so-called “challenge trials”, the Financial Times cited people involved in the project as saying. Britain said it was working with partners on the potential for human challenge trials without commenting on a specific plan.

AstraZeneca and Sanofi and Moderna , among the leading vaccine developers, have said their vaccine candidates were not involved in the programme.

U.S. biotech firm Inovio Pharmaceuticals also said it was not involved while Johnson & Johnson said it was evaluating the potential benefit of a human challenge trial but would not comment on the British plans.

The World Health Organisation was not involved in such studies, a spokesman said on Thursday.

In a paper here published in May, the WHO said challenge trials could be risky even if limited to young, healthy adults because too little is known about how COVID-19 progresses and there are no specific treatments apart from Gilead's remdesivir.

U.S.-based advocacy group 1Day Sooner, which is lining up volunteers and is lobbying for challenge trials, in a media briefing on Thursday said it did not have confirmation about which vaccines had been eyed for testing in Britain.

Leading vaccine makers have each recruited tens of thousands of volunteers in late-stage trials that rely on accidental infections to yield results on efficacy. (Additional reporting by Trisha Roy and Sri Kalyani Manojna Maddipatla; editing by Thomas Seythal and Alexandra Hudson)