Continued increase in mumps activity, particularly in universities/colleges
The number of mumps notifications in Ireland continues to escalate, with 547 mumps notifications reported this year (as of 27/11/2014) compared to a total of 223 mumps notifications in 2013. The most recent upsurge coincides with the beginning of the 2014-2015 academic term (week 30). A majority of mumps cases are associated with schools/universities/colleges.
The highest number of notifications since week 30 is among individuals aged 15-24 years of age, with a particular peak in those aged 19 and 20 years of age. Among the notified mumps cases in the 15-24 year age group since week 30 the number of MMR doses that are reported (not all are validated) are as follows; three doses (2.3%), two doses (49.2%), one dose (17.1%), no dose (6.4%) and unknown vaccination status (25%).
Although the proportion of cases with mumps who now self-report two doses of MMR vaccine has increased in recent years (in comparison to the outbreak in 2004-2005), the current mumps outbreaks demonstrates that outbreaks may occur in highly vaccinated populations. Similar outbreaks in highly vaccinated populations have been reported in the USA and the UK. However, there is good evidence to indicate that the size of the outbreaks is much less when a majority of the population have had two doses of MMR.
International evidence has shown that during mumps outbreaks in highly vaccinated communities, the proportion of people who get mumps among those fully vaccinated is much lower than the proportion who get mumps among those who were incompletely or never vaccinated with a mumps vaccine.
Mumps infection after vaccination may occur because the vaccine recipients did not develop immunity after vaccination (primary vaccine failure) or there may be some waning immunity. Two doses of MMR vaccine are estimated to be 88% effective (range: 66-95%) in preventing mumps. Vaccine still offers the best protection there is to mumps.
MMR vaccine is free (administration charges may apply for certain age groups). The first dose is normally given at 12 months of age and the second dose at school entry (4-5 years of age). Any teenager/young adult who may not have received two doses of MMR vaccine is encouraged to speak with their GP or student health service.
Mumps virus is spread through respiratory droplets and direct contact with others who have the infection. The risk of spreading the virus increases the longer and the closer the contact is with someone who has the infection. Mumps is transmitted from an infected individual from about two days before symptom onset to five days after.
Anyone who develops mumps should stay at home for the five days after disease onset to prevent spreading the infection to others. Additional measures include good respiratory etiquette and hand washing.
HPSC: MMR and Mumps
HPSC: Latest information on outbreaks in Ireland
CDC, US: Mumps outbreaks in the USA