The Sunday Times reported this week that Andrew Wakefield, the doctor who published his findings of a possible link between the MMR vaccine (measles, mumps, and rubella) and Autism in children, appears to have essentially falsified his data by misinterpreting patient information. Although the study, published in The Lancet in 1998, only involved 12 children, the results of the study were sensationalized by the media, causing fear in many parents. This led to a 12% decrease in MMR vaccinations of children (dropped from 92% to below 80%, well below the 95% "herd immunity" requirement to protect the general population from measles). As a result, we've begun to see a rise in measles--the number of confirmed cases jumped from 56 cases in the UK in 1998 to 1,348 in 2008! Wakefield and his research partners have not confessed to any wrongdoing, but the investigation continues.
This is a perfect example of misconduct in reseach since we're talking about research ethics this week. See the article here. If you're interested, there's a ScienceBlogs thread discussing the issue here.