Outbreak of Mumps Infection in Oban, Scotland. November 2010 to January 2011

1. Outbreak of Mumps Infection in Oban, Scotland. November 2010 to January 2011 J. Walker, S. Huc, K. Sinka, A. Tissington and K. Oates

2. Outbreak description • 119 cases of mumps infection were detected around the Oban area between the 29 November 2010 and 31 January 2011 • In mid December, following identification of an outbreak, all general practices in Oban area contacted and asked to notify cases directly to health protection team • Median age of cases - 20 years • Many cases notified over the Christmas/New Year holiday period, when young people return from work and university • By end of January, more cases in Oban area (n=119), than the whole of the rest of Scotland (n=90)

3. Mumps cases by onset date, Oban outbreak, Nov 2010 – Jan 2011, n = 119

4. Background • Mumps, caused by paromyxovirus • Mainly causes parotitis • Can also cause orchitis, pancreatitis, meningitis • Notifiable disease – reporting to health boards • Before vaccination available, typically 3 yearly outbreaks in under 10s

5. Image of mumps virus protein, Welcome Images

6. Vaccination • Immunisation introduced to the UK in 1988 as a single dose of MMR for 12-15 months • 1996 two dose schedule introduced • Uptake rates for first dose MMR at 24 months: 93.7% for Scotland, 91.5% for Oban area (year ending March 2010)

7. Vaccination • Following vaccine controversy rates post 1998 fell reaching a low in Scotland of 88.5% and a low in Argyll of 85.6%. • This cohort, who would have been due vaccination in 1998 – 2003 would now be 8 – 14 years old.

8. Data from table HPS website available at http://www.hps.scot.nhs.uk/immvax/mumps.aspx

9. Confirmed cases of mumps in Scotland by year of diagnosis (horizontal axis) and year of birth (vertical axis)n= 7049 to 31st Oct 2011 (data from Alison Potts HPS - personal communication) Low risk (highly vaccinated) Intermediate risk (mostly well vaccinated) High risk (patchy vaccination, low exposure to mumps) Intermediate risk (patchy vaccination but exposure to mumps) Low risk (high exposure to mumps)

10. Procedure following notification Normally: • A case of mumps is notified and an oral fluid/salivary testing kit is sent out to GP practice • Patient is recalled for testing • Kits sent off to HPA in London for laboratory confirmation, then result after 4-6 weeks • Vaccination status not routinely recorded when cases are notified During Outbreak: • Rapid Lab diagnosis on first cases then clinical diagnosis only • 18 were laboratory confirmed and 101 were clinically diagnosed • Did collect vaccination history

11. Health Protection activity during period of increased notifications • After the first few cases we contacted all local practices and asked them to contact us promptly and directly about new cases • We got a vaccination history of each case • We initially requested information on vaccination batch numbers to check on “ineffective” batches– however this soon became unnecessary • Parents of children aged 5 – 18 years sent a GP letter and reminded of offer to be vaccinated with two doses of MMR

12. Case information • Cases n=119, 63 females and 56 males • Highest incidence 13-19 year olds (range 4 – 71 years) • 3 cases had complications ( 2 orchitis, 1 pancreatitis) • Vaccination status known for 116 / 119 • Two doses of MMR n = 53 • One dose of MMR n = 33 • No doses of MMR n = 30 • For those who had two doses, date of vaccination ranged from 28 Sept 1989 – 13 May 2008 • For those who had one dose, date of vaccination ranged from 5 Dec 1988 – 23 February 2009

13. Mumps cases by age and MMR vaccination status, Oban outbreak, Nov 2010 – Jan 2011, n = 119

14. Results • Anecdotally index case student at Dundee Univ, attended former high school dance and after party • Strain involved was genotype G5 – common UK • The majority of cases under 22 years had received two doses of vaccine, 53 / 80 (66%) • Among those aged 12 or under, 8 / 9 had received two doses (89%) 45% (n= 53) of all cases had received two doses of MMR

15. Vaccination status of laboratory confirmed mumps cases diagnosed in Scotland between 2009 and 2011, by age group n=1408, to 31st October 2011(data from Alison Potts, HPS – personal communication)

16. Discussion • Anecdotally not all those affected presented to primary care – numbers may be an underestimate • Strengths of study: - well documented immunisation records for almost all cases - good relationship with primary care, enabled good follow-up of cases - letters to local parents (some came for MMR) • Main limitation of our study: - low number of laboratory confirmed cases

17. Discussion 2 • The 45% who were fully vaccinated in our study is: • higher than reports from England and Wales (29%, 31%)[1],[2] • lower than a report from the Netherlands, 61% [3] and a report from the US 75% [4] • In our cohort, in the 13 – 19 year age group, 76% affected had received two doses of MMR

18. Discussion 3 Published estimates of MMR vaccine efficacy of mumps component vary • 88% for one dose and 95% for two doses [3] • 64% for one dose and 88% for two doses [6] Waning immunity has been noted in older vaccinated individuals

19. Conclusion • Unvaccinated individuals combined with those whose immunity had waned to provide a vulnerable cohort. • These cases highlight the importance of ensuring high uptake of the recommended two doses of MMR. • Imply a need for further research into long-term mumps immunity in those partially or fully vaccinated in order to inform future vaccination programmes. • Although numbers in our cohort are small they add to growing body of evidence which suggests that immunity to the mumps component of the vaccine may wane over time [3-6] • HPS paper for JCVI adolescent subgroup

20. References • [1] Walker J, Huc S, Sinka K, Tissington A, Oates K. Ongoing outbreak of mumps infection in Oban, Scotland, November 2010 to January 2011. Eurosurveillance, 2011; 16(8): pii = 19803. • (2) Yung C., Bukasa A., Brown K., Pebody R. Public Health advice based on routine mumps surveillance in England and Wales. Eurosurveillance, 2010 15 (38):pii=19669 • [3] Cohen C., White J.M., Savage E.J., Glynn J.R., Choi Y., Andrews N., Brown D., Ramsay M.E., Vaccine effectiveness estimates, 2004-2005 mumps outbreak, England. Emerg Infect Disease, 2007 Jan 13 (1):12-7. • [4] Whelan J., van Binnendijik R., Geenland K., Fanoy E., Khargi M., Yap K., Boot H., Valtman N., Swaan C., van der Bij A., de Melker H., Hahne S. Ongoing mumps outbreak in a student population with a high vaccination coverage, Netherlands, 2010. Euro surveillance, 2010; 15 (17) :pii=19554. • [5] Centres for Disease Control and Prevention. Update: Mumps Outbreak – New York and New Jersey, June 2009 – January 2010. MMWR 2010; 59 [ 126 – 129] • [6] Harling R., White J.M., Ramsaya M.E., Macsween K.F. and van den Bosch C. The effectiveness of mumps component of the MMR vaccine: a case control study. Vaccine 2005 Jul 1l 23 (31) :4070 – 4.

21. Acknowledgements Jean Walker, Sara Huc, Katy Sinka, Abhayadevi Tissington Lorraine McKee, HPN NHS Highland Pauline Jesperson Practice Manager Oban All GPs in North Argyll Alison Potts, HPS Judith Tait, ISD