In the first six months of 2011, there were 23 laboratory-confirmed measles cases in Scotland and one probable case, Health Protection Scotland (HPS) figures show.
In 2010, there were 10 confirmed cases and one probable case.
Nine of the cases in 2011 occurred in those aged 20-24, whereas there were no cases in this age group in 2010, just one in 2009 and two in 2008.
HPS said that, overall, measles cases were ‘not substantially higher’ than levels seen in recent years.
But a statement by the agency added: ‘There has, however, been a shift in the age group affected. The median age of cases so far in 2011 is 20.5 years.'
The HPA said that most confirmed cases in previous years have been in children aged under 15. But in 2011 only six confirmed cases were in that age group and only two were in children aged 5-14.