The outbreaks are occurring predominantly in 19-23 year olds, but cases are also occurring in susceptible children, underlining the importance of ensuring that all children and young adults have had two doses of the MMR vaccine.
In the first paper (Savage et al), researchers from the Health Protection Agency report that in 2004, the number of mumps notifications in England and Wales increased to 16,436 from 4,204 in 2003. Most cases were in young adults born before 1988, who would not have been routinely scheduled for MMR during childhood.
The highest attack rate was in those born between 1983 and 1986, who were too old to be offered MMR vaccination routinely when it was introduced in 1988, although some may have received one dose of MMR as part of a catch-up programme at school entry.
In the second paper (Gupta et al), the authors suggest that cases in younger children may occur due to the recent fall in uptake of the MMR vaccine among 2 year olds - from around 92% in early 1995 to around 80% in 2003-4, and as low as 60% in some parts of London.
Both papers conclude that the current, two dose MMR schedule is effective in preventing mumps. They also suggest that no opportunity should be missed to offer MMR vaccine to the age group at highest risk, such as when entering school or university.