1. Mumps Vaccine Effectiveness During an Outbreak in New York City
Kara Livingston, Jennifer Rosen, Jane Zucker, Christopher Zimmerman
NYC Department of Health & Mental Hygiene
Bureau of Immunization

2. Mumps Viral illness Often presents with parotitis
Rare complications: orchitis, encephalitis,
aseptic meningitis, hearing loss
Up to 30% of infections asymptomatic
Incubation period: range 12-25d
Preventable through vaccination

3. Mumps Vaccine Vaccine introduced in 1967
Mumps cases in US declined 99.6% after introduction of vaccine
Combined measles-mumps-rubella vaccine (MMR)
1st dose age 12m, 2nd dose age 4-6y
Outbreaks still occur in vaccinated populations
Largest being 2006 outbreak in the mid-West with ~6,000 cases
Waning immunity
Crowding
Decline in vaccine effectiveness

4. Mumps Vaccine Effectiveness (MVE)
Initial clinical trials
95% efficacy of monovalent vaccine
MVE calculated in various settings and age groups
MVE estimates
One-dose: 75%-91%
MVE estimates
One-dose: 64%-88%
Two-dose: 83%-92%
Hilleman, NEJM 1968; Cohen, EID 2007; Schaffzin, Pediatrics 2007; Marin, Vaccine 2008; Castilla, Vaccine 2009; Dominguez, Vaccine 2010

5. New York City (NYC) Outbreak
NYC experienced an outbreak of mumps in in a vaccinated population
This outbreak afforded an opportunity to assess
Risk factors for mumps in households
Mumps vaccine effectiveness (MVE)

6. Confirmed Mumps Cases by Parotitis Onset Date, NYC, July 2009 – July 2010

7. Methods Cases identified via routine surveillance
reported by providers and labs
Standard surveillance investigations
9/1/09 – 12/31/09: expanded household investigations
Documented vaccination status on household contacts
3/10- 4/10: follow-up calls to collect information on illness status, residence, # of bedrooms

8. Mumps Case Definitions
Surveillance clinical case definition
Acute onset, unilateral or bilateral tender, self-limited swelling of parotid or other salivary glands, lasting >2 days, without other apparent cause
Clinically compatible illness reported by interviewee at follow-up
Sick since 9/09 with doctor diagnosed mumps or cheek swelling lasting > 2 days

9. Methods: Study definitions
Index case
The first case identified in household as part of routine surveillance, with earliest onset of symptoms
Co-primary case
Mumps cases with onset prior to earliest incubation period (< 9 days) after onset of index’s illness
Secondary case
Mumps cases with onset > 9 days after index’s illness

10. Methods: Household Exclusion Criteria
Initial investigation: excluded if index
Lived alone or in dormitory (24)
Did not speak English (1)
Unreachable (84)
Unable/unwilling to provide information on household contacts (285)
At follow-up: excluded if unreachable/refused (127)
After follow-up: excluded if index didn’t sleep in home (35)

11. Methods Univariate and multivariate analyses to examine risk factors
Age, time from last MMR dose, density
Secondary household attack rates (AR) to calculate MVE
MVE=([ARunvx-ARvx]/ARunvx)*100%
Excluded children age < 5 y (n=342)
Children < 5 were excluded from VE calculation based on the epidemiology of mumps which has shown that even in the pre-vaccine era, clinical mumps disease is rare among those under-five years of age
In order to be considered valid, doses had to be administered no earlier than 4 days before the first birthday and at least 28 days after a previous MMR dose.

12. Results: Descriptive Data
311 households
Median 7 (2-16) people
Median 4 (1-8) bedrooms
AR ranged from7%-100% of household
2,176 household residents
Median age: 13 (0-85) years
462 (21%) met definition for mumps
311 index, 23 co-primary, 93 secondary, 35 unknown (no onset date)
50% of non-index cases reported via surveillance

13. Vaccination Status of Household Members by Age Group
89%
74%
88%
89% 4-18 year olds had one or two doses
74% 4-18 year olds had two doses
88% adults 19+ had unknown vaccination history
Age Group (years)

14. Risks for Disease Secondary Cases Total AR (%) Odds Ratio (95% CI)
Age group
0-4 years
488
0.0
Referent
5-9 years 17
224
7.6
1.4 ( )
10-14 years 29
311
9.3
3.4 ( )
15-19 year 14
341
4.1
2.7 ( )
20 + years 10
342
2.9
1.6 ( )

15. Risks for Disease Secondary Cases Total AR (%) Odd Ratio (95% CI)
Time from last MMR
<5 years 31
660
4.7
Referent
5-10 years 27
348
7.8
1.7 ( )
>10 years 6
161
3.7
0.8 ( )
Household Density
< 2 people/ bedroom 53
951
5.6
> 2 people/ bedroom 37
808
4.6
0.8 ( )

16. Likelihood of secondary mumps among household contacts by age group
Age group (years)
# Mumps cases
Total household members
Odds Ratio*
(95% CI)
p-value
0-4
488
Referent
5-9 17
224
1.4 ( )
0.4263
10-14 29
311
3.4 ( )
0.0010
15-19 14
341
2.7 ( )
0.0155
20+ 10
342
1.6 ( )
0.2527
*Generalized estimating equations; controlled for household density and time since last MMR

17. One and Two-Dose Mumps Vaccine Effectiveness
# MMR Doses
# Mumps cases
Total household members AR
VE %
95% CI 6 20
0.300 -- 1
116
0.052
82.8 2 43
697
0.062
79.4
Excludes children age <5y and persons with unknown MMR history

18. Summary Age was associated with mumps
Higher likelihood of mumps among adolescents
Did not find an associations between:
Time from vaccination and mumps
Household density (people/bedroom)
Two-dose MVE among household contacts aged > 5y was 79.4% ( )

19. Limitations MVE for clinical mumps only
44% of secondary cases determined by follow-up report only
May not have been equal exposure to disease for all household members
Many adults lacked MMR records and so were not included in the analysis
Transmission of mumps in schools may have contributed to the high proportion of cases in school aged children.

20. Conclusions We found MMR vaccine effective at preventing disease
Our MVE estimate fell within the range found in other recent studies
Higher MMR coverage may have helped prevent this outbreak
A better understanding of factors leading to outbreaks and outbreak control measures among vaccinated individuals is needed

21. Acknowledgments CDC/CSTE Applied Epidemiology Fellowship
Kara Livingston, MPH
NYC DOHMH
Christopher M. Zimmerman, MD, MPH
Jane R. Zucker, MD, MSc
Jennifer Rosen, MD
Kisha Cummings, MPH
Margaret Doll, MPH
Joseph Egger, PhD, MA
Jim Hadler, MD, MPH
New York City Call Center
BOI Surveillance Unit
CDC
Gregory Armstrong, MD, MSCE
Mumps cases and their families

22. Questions?