She and Mr. Crang, her boyfriend, used the money to visit Croatia, Israel and her family in Latvia. They have both signed up for a second vaccine trial that will pay for his laser eye surgery and then a trip together to Australia.

Faye Francis, a 42-year-old psychiatric nurse, said she felt “happy to be doing something that could help millions of poor people who haven’t got antibiotics.”

“But I won’t lie,” she added. “The money was a big part of it.”

She used it to take her husband and three children on a vacation in Cornwall “and buy a few bits for the car and the house.”

Her mother was not happy. “She said, ‘That’s ridiculous – don’t think about the money, think about your health!’ ” Mrs. Francis said. “And people were telling me horror stories about things they’d seen on TV. So I didn’t go on about it to my parents after that.”

She got sick and “felt rotten for about a week” with a 101-degree fever, headache and nausea.

“But I still went to work,” she said. “I felt a bit guilty about not going when I had an illness I’d given myself.”

Because her job is to distribute medicine on home visits, no patients were endangered, she said. (Mr. Duggan, the medical student, was also quick to say that he took part during a period when he was not assigned to hospital rounds.)

“They don’t let you do it if you’ve got preschoolers or children in nappies,” Mrs. Francis said. “And you’re not allowed to handle food, so my husband did all the cooking.”

During the worst week, “you feel sorry for yourself and you say ‘I’m never doing that again,’ ” she said. “And then it’s like childbirth – you get amnesia, and you do it again. I’ve just signed up for a second trial.”