Modeling the population-level impact of a third dose of MMR vaccine on a mumps outbreak at the University of Iowa.

Mumps outbreaks among fully vaccinated young adults have raised questions about potential waning of immunity over time and need for a third dose of the measles, mumps, rubella (MMR) vaccine. However, there are currently limited data on real-life effectiveness of the third-dose MMR vaccine in preventing mumps. Here, we used a deterministic compartmental model to infer the effectiveness of the third-dose MMR vaccine in preventing mumps cases by analyzing the mumps outbreak that occurred at the University of Iowa between August 24, 2015, and May 13, 2016. The modeling approach further allowed us to evaluate the population-level impact of vaccination by different timing in relation to the start of the outbreak and varied coverage levels, and to account for potential sources of bias in estimating vaccine effectiveness. We found large uncertainty in vaccine effectiveness estimates; however, our models showed that early introduction of a third dose of MMR vaccine during a mumps outbreak can be effective in preventing transmission. School holidays, such as the winter break, likely played important roles in preventing mumps transmission.

Rapid Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 in Detention Facility, Louisiana, USA, May-June, 2020.

To assess transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a detention facility experiencing a coronavirus disease outbreak and evaluate testing strategies, we conducted a prospective cohort investigation in a facility in Louisiana, USA. We conducted SARS-CoV-2 testing for detained persons in 6 quarantined dormitories at various time points. Of 143 persons, 53 were positive at the initial test, and an additional 58 persons were positive at later time points (cumulative incidence 78%). In 1 dormitory, all 45 detained persons initially were negative; 18 days later, 40 (89%) were positive. Among persons who were SARS-CoV-2 positive, 47% (52/111) were asymptomatic at the time of specimen collection; 14 had replication-competent virus isolated. Serial SARS-CoV-2 testing might help interrupt transmission through medical isolation and quarantine. Testing in correctional and detention facilities will be most effective when initiated early in an outbreak, inclusive of all exposed persons, and paired with infection prevention and control.

Pediatricians' Knowledge and Practices Related to Mumps Diagnosis and Prevention.

OBJECTIVES: To assess pediatricians' mumps knowledge and testing practices, to identify physician and practice characteristics associated with mumps testing practices, and to assess reporting and outbreak response knowledge and practices. STUDY DESIGN: Between January and April 2020, we surveyed a nationally representative network of pediatricians. Descriptive statistics were generated for all items. The χ2 test, t tests, and Poisson regression were used to compare physician and practice characteristics between respondents who would rarely or never versus sometimes or often/always test for mumps in a vaccinated 17-year-old with parotitis in a non-outbreak setting. RESULTS: The response rate was 67% (297 of 444). For knowledge, more than one-half of the pediatricians responded incorrectly or "don't know" for 6 of the 9 true/false statements about mumps epidemiology, diagnosis, and prevention, and more than one-half reported needing additional guidance on mumps buccal swab testing. For testing practices, 59% of respondents reported they would sometimes (35%) or often/always (24%) test for mumps in a vaccinated 17-year-old with parotitis in a non-outbreak setting; older physicians, rural physicians, and physicians from the Northeast or Midwest were more likely to test for mumps. Thirty-six percent of the pediatricians reported they would often/always report a patient with suspected mumps to public health authorities. CONCLUSIONS: Pediatricians report mumps knowledge gaps and practices that do not align with public health recommendations. These gaps may lead to underdiagnosis and underreporting of mumps cases, delaying public health response measures and contributing to ongoing disease transmission.

Investigation and Serologic Follow-Up of Contacts of an Early Confirmed Case-Patient with COVID-19, Washington, USA.

We describe the contact investigation for an early confirmed case of coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in the United States. Contacts of the case-patient were identified, actively monitored for symptoms, interviewed for a detailed exposure history, and tested for SARS-CoV-2 infection by real-time reverse transcription PCR (rRT-PCR) and ELISA. Fifty contacts were identified and 38 (76%) were interviewed, of whom 11 (29%) reported unprotected face-to-face interaction with the case-patient. Thirty-seven (74%) had respiratory specimens tested by rRT-PCR, and all tested negative. Twenty-three (46%) had ELISA performed on serum samples collected ≈6 weeks after exposure, and none had detectable antibodies to SARS-CoV-2. Among contacts who were tested, no secondary transmission was identified in this investigation, despite unprotected close interactions with the infectious case-patient.

Mumps Cases Disproportionately Affecting Persons Living with HIV Infection and Men Who Have Sex with Men - Chicago, Illinois, 2018.

During January 1-March 2, 2018, the number of mumps cases among adults reported to the Chicago Department of Public Health (CDPH) doubled compared with the same period in 2017. In response, CDPH created a supplementary questionnaire to collect additional information on populations affected and potential transmission routes. An epidemiologic analysis of routine and supplementary data, including spatiotemporal analysis, was performed to describe mumps cases reported to CDPH during 2018. A fourfold increase in mumps cases was reported during 2018 compared with 2017, with men who have sex with men (MSM) and persons living with human immunodeficiency virus (HIV) infection disproportionately represented among cases. A spatiotemporal, residential cluster was identified in a 9-square-mile area within six adjacent communities. The majority of persons affected were MSM, and this area was visited by many other persons with mumps diagnoses. Spatiotemporal analyses could be used in real time to identify case clusters to target public health response efforts, including to guide recommendations for additional measles, mumps, and rubella (MMR) vaccine and to identify specific transmission venues.

Public Health Response to COVID-19 Cases in Correctional and Detention Facilities - Louisiana, March-April 2020.

Correctional and detention facilities face unique challenges in the control of infectious diseases, including coronavirus disease 2019 (COVID-19) (1-3). Among >10 million annual admissions to U.S. jails, approximately 55% of detainees are released back into their communities each week (4); in addition, staff members at correctional and detention facilities are members of their local communities. Thus, high rates of COVID-19 in correctional and detention facilities also have the potential to influence broader community transmission. In March 2020, the Louisiana Department of Health (LDH) began implementing surveillance for COVID-19 among correctional and detention facilities in Louisiana and identified cases and outbreaks in many facilities. In response, LDH and CDC developed and deployed the COVID-19 Management Assessment and Response (CMAR) tool to guide technical assistance focused on infection prevention and control policies and case management with correctional and detention facilities. This report describes COVID-19 prevalence in correctional and detention facilities detected through surveillance and findings of the CMAR assessment. During March 25-April 22, 489 laboratory-confirmed COVID-19 cases, including 37 (7.6%) hospitalizations and 10 (2.0%) deaths among incarcerated or detained persons, and 253 cases, including 19 (7.5%) hospitalizations and four (1.6%) deaths among staff members were reported. During April 8-22, CMAR telephone-based assessments were conducted with 13 of 31 (42%) facilities with laboratory-confirmed cases and 11 of 113 (10%) facilities without known cases. Administrators had awareness and overall understanding of CDC guidance for prevention of transmission in these facilities but reported challenges in implementation, related to limited space to quarantine close contacts of COVID-19 patients and inability of incarcerated and detained persons to engage in social distancing, particularly in dormitory-style housing. CMAR was a useful tool that helped state and federal public health officials assist multiple correctional and detention facilities to better manage COVID-19 patients and guide control activities to prevent or mitigate transmission.

Serial Laboratory Testing for SARS-CoV-2 Infection Among Incarcerated and Detained Persons in a Correctional and Detention Facility - Louisiana, April-May 2020.

Transmission of SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), by asymptomatic and presymptomatic persons poses important challenges to controlling spread of the disease, particularly in congregate settings such as correctional and detention facilities (1). On March 29, 2020, a staff member in a correctional and detention facility in Louisiana developed symptoms† and later had a positive test result for SARS-CoV-2. During April 2-May 7, two additional cases were detected among staff members, and 36 cases were detected among incarcerated and detained persons at the facility; these persons were removed from dormitories and isolated, and the five dormitories that they had resided in before diagnosis were quarantined. On May 7, CDC and the Louisiana Department of Health initiated an investigation to assess the prevalence of SARS-CoV-2 infection among incarcerated and detained persons residing in quarantined dormitories. Goals of this investigation included evaluating COVID-19 symptoms in this setting and assessing the effectiveness of serial testing to identify additional persons with SARS-CoV-2 infection as part of efforts to mitigate transmission. During May 7-21, testing of 98 incarcerated and detained persons residing in the five quarantined dormitories (A-E) identified an additional 71 cases of SARS-CoV-2 infection; 32 (45%) were among persons who reported no symptoms at the time of testing, including three who were presymptomatic. Eighteen cases (25%) were identified in persons who had received negative test results during previous testing rounds. Serial testing of contacts from shared living quarters identified persons with SARS-CoV-2 infection who would not have been detected by symptom screening alone or by testing at a single time point. Prompt identification and isolation of infected persons is important to reduce further transmission in congregate settings such as correctional and detention facilities and the communities to which persons return when released.

CDC Guidance for Use of a Third Dose of MMR Vaccine During Mumps Outbreaks.

CONTEXT: In response to numerous mumps outbreaks reported throughout the United States in 2016 and 2017, the Advisory Committee on Immunization Practices (ACIP) recommended a third dose of measles, mumps, and rubella (MMR) vaccine for groups of persons determined by public health authorities to be at increased risk for acquiring mumps because of an outbreak. OBJECTIVE: To provide guidance for health departments when implementing the ACIP recommendation. DESIGN: Draft guidance was developed by Centers for Disease Control and Prevention subject matter experts based on technical consultations with health departments and review of published and unpublished data regarding mumps outbreaks. The guidance was finalized based on input from experts from the ACIP Mumps Work Group and local and state epidemiologists through the Council of State and Territorial Epidemiologists and the National Association of County and City Health Officials. RESULTS: We developed guidance to assist public health authorities when determining which groups are at increased risk for acquiring mumps and should receive a third dose of MMR vaccine. During outbreaks, public health authorities identify groups of persons with known or likely close contact exposure to a mumps patient. Then, evidence of transmission and likelihood of transmission in a group's setting can be used to determine whether these groups are at increased risk. Additional epidemiologic and implementation factors may also be considered. All persons in the group at increased risk for acquiring mumps should receive a dose of MMR vaccine, including those with unknown vaccination status or those who have evidence of presumptive immunity other than documented 2 doses of MMR vaccine; no additional dose is recommended for persons who had received 3 or more doses before the outbreak. CONCLUSION: This guidance provides a framework for public health authorities to use when considering a third dose of MMR in response to mumps outbreaks while maintaining flexibility to incorporate local factors related to individual outbreaks.

Health Departments' Experience With Mumps Outbreak Response and Use of a Third Dose of Measles, Mumps, and Rubella Vaccine.

CONTEXT: During January 2016 to June 2017, US health departments (HDs) reported 150 mumps outbreaks. Most occurred among populations with high 2-dose measles, mumps, and rubella (MMR) vaccine coverage, prompting the Advisory Committee on Immunization Practices to examine the evidence for use of a third dose of MMR vaccine. OBJECTIVE: To evaluate HD experiences with mumps outbreak control and use of a third MMR dose during outbreaks. DESIGN: An online survey assessing mumps outbreak characteristics, outbreak response measures, challenges, and lessons learned from previous outbreaks was distributed to all 81 Council of State and Territorial Epidemiologists member HDs in August 2017. RESULTS: Sixty-one (75%) HDs responded; 46 (75%) had experience with ≥1 mumps outbreak(s) during January 2016 to August 2017. Twenty (43%) HDs recommended a third or outbreak MMR dose during mumps outbreaks; of these, 19 completed the section on use of a third dose and 8 (40%) rated the intervention "somewhat effective" or better. Health departments that used a third/outbreak dose suggested implementing the recommendation early and to a targeted group. Forty-three (73%) HDs reported having a policy for excluding persons without presumptive immunity from outbreak settings; of these, 37 (86%) had some degree of legal authority to implement this policy. Exclusion compliance improved with the use of personalized notification letters, focus groups of excluded persons and the community, and standardized messaging. Other outbreak control measures included cohorting of exposed or susceptible persons, mobile vaccination clinics and home visits, contact monitoring via text messaging, and facilitating student isolation with meal delivery and excused class absences. CONCLUSIONS: Our study revealed heterogeneity across HDs' mumps outbreak responses but also identified common challenges that will inform future Centers for Disease Control and Prevention guidance. These results were considered in the October 2017 Advisory Committee on Immunization Practices recommendation for use of a third dose of MMR vaccine for persons at increased risk for mumps during an outbreak and in the development of Centers for Disease Control and Prevention guidance for HDs when applying the Advisory Committee on Immunization Practices recommendation.

Differences in gram-positive bacterial colonization and antimicrobial resistance among children in a high income inequality setting.

BACKGROUND: Staphylococcus aureus and beta-hemolytic streptococci (BHS) diseases disproportionately affect populations in middle/low-income countries. To assess if this disparity is reflected in colonization by these organisms, we compared their colonization frequency among children from different socioeconomic status (SES) communities in a city with high income inequality. METHODS: Between May-August 2014, we collected nasal and throat swabs to investigate S. aureus and BHS colonization among children who attended private and public pediatric clinics. Patients were classified as high SES, middle/low SES, and slum residents. We investigated the antimicrobial resistance profile, the SCCmec types and the presence of PVL genes among methicillin-resistant S. aureus (MRSA). We also examined the antimicrobial resistance profile and serogroups of BHS. RESULTS: Of 598 children, 221 (37%) were colonized with S. aureus, of which 49 (22%) were MRSA. MRSA colonization was higher in middle/low SES (n = 18; 14%) compared with high SES (n = 17; 6%) and slum (n = 14; 8%) residents (p = 0.01). All MRSA strains were susceptible to clindamycin, nitrofurantoin, and rifampin. The highest non-susceptibility frequency (42.9%) was observed to erythromycin. SCCmec type V was only found in isolates from high SES children; types I and II were found only in middle/low SES children. Ten (20%) MRSA isolates carried PVL genes. Twenty-four (4%) children were BHS carriers. All BHS (n = 8) found in high SES children and six (67%) isolates from slum patients belonged to group A. All group B streptococci were from middle/low SES children, corresponding to five (71%) of the seven BHS isolated in this group. BHS isolates were susceptible to all drugs tested. CONCLUSIONS: Children from different SES communities had distinct bacterial colonization profiles, including MRSA carriage. Public health officials/researchers should consider SES when assessing disease transmission and control measures.

Population structure of Streptococcus pneumoniae colonizing children before and after universal use of pneumococcal conjugate vaccines in Brazil: emergence and expansion of the MDR serotype 6C-CC386 lineage.

Objectives: To determine the population structure and change in drug resistance of pneumococci colonizing children before and after the introduction of the 10-valent and 13-valent pneumococcal conjugate vaccines (PCV10/13) in Brazil. Methods: We used MLST to analyse 256 pneumococcal isolates obtained from children aged <6 years before (2009-10; n = 125) and after (2014; n = 131) the introduction of the PCV10 and PCV13. Antimicrobial susceptibility and capsular types were previously determined. Results: We identified 97 different STs. Ninety (35.2%) isolates were related to international clones. The most frequent lineages were serogroup 6-CC724 (where CC stands for clonal complex) and the MDR serotype 6C-CC386 in the pre- and post-PCV10/13 periods, respectively. Penicillin-non-susceptible pneumococci (PNSP) formed 24% and 38.9% of the pre- and post-PCV10/13 isolates, respectively (P = 0.01). In the pre-PCV10/13 period, serotype 14-ST156 was the predominant penicillin-non-susceptible lineage, but it was not detected in the post-PCV10/13 period. Serotype 14-ST156 and serotype 19A-ST320 complex isolates had the highest penicillin and ceftriaxone MICs in the pre- and post-PCV10/13 periods, respectively. In turn, serotype 6C-CC386 comprised almost 30% of the PNSP and over 40% of the erythromycin-resistant isolates (MIC >256 mg/L) in the post-PCV10/13 period. Conclusions: Although PNSP strains were polyclonal, most resistant isolates belonged to a single genotype from each period. Higher erythromycin resistance prevalence (42%) in the post-PCV10/13 period was mainly attributed to MDR serotype 6C-CC386. Ongoing surveillance of pneumococcal clonal composition is important to evaluate PCV use outcomes and to identify factors other than PCVs that drive pneumococcal drug resistance evolution.

Recommendation of the Advisory Committee on Immunization Practices for Use of a Third Dose of Mumps Virus-Containing Vaccine in Persons at Increased Risk for Mumps During an Outbreak.

A substantial increase in the number of mumps outbreaks and outbreak-associated cases has occurred in the United States since late 2015 (1,2). To address this public health problem, the Advisory Committee on Immunization Practices (ACIP) reviewed the available evidence and determined that a third dose of measles, mumps, rubella (MMR) vaccine is safe and effective at preventing mumps. During its October 2017 meeting, ACIP recommended a third dose of a mumps virus-containing vaccine* for persons previously vaccinated with 2 doses who are identified by public health authorities as being part of a group or population at increased risk for acquiring mumps because of an outbreak. The purpose of the recommendation is to improve protection of persons in outbreak settings against mumps disease and mumps-related complications. This recommendation supplements the existing ACIP recommendations for mumps vaccination (3).

Foodborne Disease Outbreaks in Correctional Institutions-United States, 1998-2014.

OBJECTIVES: To present the first update on the epidemiology of US foodborne correctional institution outbreaks in 20 years. METHODS: We analyzed data from the Centers for Disease Control and Prevention's Foodborne Disease Outbreak Surveillance System to describe correctional institution outbreaks from 1998 to 2014 and compare them with other foodborne outbreaks. RESULTS: Two hundred foodborne outbreaks in correctional institutions were reported, resulting in 20 625 illnesses, 204 hospitalizations, and 5 deaths. Median number of outbreak-associated illnesses per 100 000 population per year was 45 (range = 11-141) compared with 7 (range = 4-10) for other outbreaks. These outbreaks accounted for 6% (20 625 of 358 330) of outbreak-associated foodborne illnesses. Thirty-seven states reported at least 1 outbreak in a correctional institution. Clostridium perfringens (28%; 36 of 128) was the most frequently reported single etiology. The most frequently reported contributing factor was food remaining at room temperature (37%; 28 of 76). CONCLUSIONS: Incarcerated persons suffer a disproportionate number of outbreak-associated foodborne illnesses. Better food safety oversight and regulation in correctional food services could decrease outbreaks. Public Health Implications. Public health officials, correctional officials, and food suppliers can work together for food safety. Clearer jurisdiction over regulation of correctional food services is needed.

Risk factors for differential outcome following directly observed treatment (DOT) of slum and non-slum tuberculosis patients: a retrospective cohort study.

BACKGROUND: Brazil's National Tuberculosis Control Program seeks to improve tuberculosis (TB) treatment in vulnerable populations. Slum residents are more vulnerable to TB due to a variety of factors, including their overcrowded living conditions, substandard infrastructure, and limited access to healthcare compared to their non-slum dwelling counterparts. Directly observed treatment (DOT) has been suggested to improve TB treatment outcomes among vulnerable populations, but the program's differential effectiveness among urban slum and non-slum residents is not known. METHODS: We retrospectively compared the impact of DOT on TB treatment outcome in residents of slum and non-slum census tracts in Rio de Janeiro reported to the Brazilian Notifiable Disease Database in 2010. Patient residential addresses were geocoded to census tracts from the 2010 Brazilian Census, which were identified as slum (aglomerados subnormais -AGSN) and non-slum (non-AGSN) by the Census Bureau. Homeless and incarcerated cases as well as those geocoded outside the city's limits were excluded from analysis. RESULTS: In 2010, 6,601 TB cases were geocoded within Rio de Janeiro; 1,874 (27.4 %) were residents of AGSN, and 4,794 (72.6 %) did not reside in an AGSN area. DOT coverage among AGSN cases was 35.2 % (n = 638), while the coverage in non-AGSN cases was 26.2 % (n = 1,234). Clinical characteristics, treatment, follow-up, cure, death and abandonment were similar in both AGSN and non-AGSN TB patients. After adjusting for covariates, AGSN TB cases on DOT had 1.67 (95 % CI: 1.17, 2.4) times the risk of cure, 0.61 (95 % CI: 0.41, 0.90) times the risk of abandonment, and 0.1 (95 % CI: 0.01, 0.77) times the risk of death from TB compared to non-AGSN TB cases not on DOT. CONCLUSION: While DOT coverage was low among TB cases in both AGSN and non-AGSN communities, it had a greater impact on TB cure rate in AGSN than in non-AGSN populations in the city of Rio de Janeiro.

Tuberculosis DALY-Gap: Spatial and Quantitative Comparison of Disease Burden Across Urban Slum and Non-slum Census Tracts.

To quantitatively assess disease burden due to tuberculosis between populations residing in and outside of urban informal settlements in Rio de Janeiro, Brazil, we compared disability-adjusted life years (DALYs), or "DALY-gap." Using the 2010 Brazilian census definition of informal settlements as aglomerados subnormais (AGSN), we allocated tuberculosis (TB) DALYs to AGSN vs non-AGSN census tracts based on geocoded addresses of TB cases reported to the Brazilian Information System for Notifiable Diseases in 2005 and 2010. DALYs were calculated based on the 2010 Global Burden of Disease methodology. DALY-gap was calculated as the difference between age-adjusted DALYs/100,000 population between AGSN and non-AGSN. Total TB DALY in Rio in 2010 was 16,731 (266 DALYs/100,000). DALYs were higher in AGSN census tracts (306 vs 236 DALYs/100,000), yielding a DALY-gap of 70 DALYs/100,000. Attributable DALY fraction for living in an AGSN was 25.4%. DALY-gap was highest for males 40-59 years of age (501 DALYs/100,000) and in census tracts with <60% electricity (12,327 DALYs/100,000). DALY-gap comparison revealed spatial and quantitative differences in TB burden between slum vs non-slum census tracts that were not apparent using traditional measures of incidence and mortality. This metric could be applied to compare TB burden or burden for other diseases in mega-cities with large informal settlements for more targeted resource allocation and evaluation of intervention programs.

High prevalence of Staphylococcus aureus and methicillin-resistant S. aureus colonization among healthy children attending public daycare centers in informal settlements in a large urban center in Brazil.

BACKGROUND: In the past decade methicillin-resistant Staphylococcus aureus (MRSA) has become increasingly prevalent in community settings. Attending a daycare center (DCC) is a known risk factor for colonization with MRSA. Brazil operates free, public DCCs for low-income families, some of which are located in census tracts defined by the Brazilian Census Bureau as informal settlements (aglomerados subnormais, AGSN). Physical and demographic characteristics of AGSNs suggest that S. aureus colonization prevalence would be higher, but little is known about the prevalence of MRSA in these settings. METHODS: We conducted a cross-sectional study to assess risk factors for S. aureus and MRSA colonization among children attending DCCs located in AGSN vs non-AGSN. Nasal swabs were collected from children aged three months to six years in 23 public DCCs in Niterói, Brazil between August 2011 and October 2012. RESULTS: Of 500 children enrolled in the study, 240 (48%) were colonized with S. aureus and 31 (6.2%) were colonized with MRSA. Children attending DCCs in AGSNs were 2.32 times more likely to be colonized with S. aureus (95% CI: 1.32, 4.08), and 3.27 times more likely to be colonized with MRSA than children attending non-AGSN DCCs (95% CI: 1.52, 7.01), adjusted for confounding variables. CONCLUSION: S. aureus and MRSA colonization prevalence among children attending DCCs in informal settlement census tracts was higher than previously reported in healthy pre-school children in Latin America. Our data suggest that transmission may occur more frequently in DCCs rather than at home, highlighting the importance of DCCs in AGSNs as potential MRSA reservoirs. This finding underscores the importance of local epidemiologic surveillance in vulnerable AGSN communities.

Mumps vaccine effectiveness of a 3rd dose of measles, mumps, rubella vaccine in school settings during a mumps outbreak -- Arkansas, 2016-2017.

Objectives: The largest mumps outbreak in the United States since 2006 occurred in Arkansas during the 2016-17 school year. An additional dose (third dose) of measles-mumps-rubella vaccine (MMR3) was offered to school children. We evaluated the vaccine effectiveness (VE) of MMR3 compared with two doses of MMR for preventing mumps among school-aged children during the outbreak. Study design: A generalized linear mixed effects model was used to estimate the incremental vaccine effectiveness (VE) of a third dose of MMR compared with two doses of MMR for preventing mumps. Methods: We obtained school enrollment, immunization status and mumps case status from school registries, Arkansas's immunization registry, and Arkansas's mumps surveillance system, respectively. We included students who previously received 2 doses of MMR in schools with ≥1 mumps case after the MMR3 clinic. We used a generalized linear mixed model to estimate VE of MMR3 compared with two doses of MMR. Results: Sixteen schools with 9272 students were included in the analysis. Incremental VE of MMR3 versus a two-dose MMR regimen was 52.7% (95% confidence interval [CI]: -3.6%‒78.4%) overall and in 8 schools with high mumps transmission it was 64.0% (95% CI: 1.2%‒86.9%). MMR3 VE was higher among middle compared with elementary school students (68.5% [95% CI: -30.2%‒92.4%] vs 37.6% [95% CI: -62.5%‒76.1%]); these differences were not statistically significant. Conclusion: Our findings suggest MMR3 provided additional protection from mumps compared with two MMR doses in elementary and middle school settings during a mumps outbreak.