Nielsen says it was unable to remove the scraped data from its database, but a company spokesman later said Nielsen had found a way to quarantine the PatientsLikeMe data to prevent it from being included in its reports for clients.

WSJ: 'Scrapers' Dig Deep for Data on the Web

The first study - involving more than 68, 000 infants aged six to 12 weeks - found a vaccine called Rotateq being developed by the pharmaceutical company Merck could safely prevent 98% of severe cases of viral diarrhoea and vomiting.

BBC: NEWS | Health | Diarrhoea vaccine tests 'hopeful'