Acceptability and feasibility of implementing the Enhanced Assess, Acknowledge, Act (EAAA) sexual assault prevention intervention on a U.S. university campus: Themes from qualitative interviews and written reflections.

Objectives: Assess the acceptability of and self-reported behavioral change from participation in a sexual assault prevention intervention on a U.S. university campus. Participants: Thirty-one undergraduate students who identified as women and opted-in to participating in both the intervention and research. Methods: In-depth interviews and written reflections were collected. Analysis was thematic with three investigators coding and reaching consensus. Results: The EAAA program was well-liked by most participants, with positive behavior changes reported. Five key themes reflecting strengths of EAAA were identified, including improved verbal communication, reduced sexual assault myths, empowerment, recognizing and responding to danger cues, and learning about healthy sexuality. Three key themes reflecting challenges were identified, including time commitment, use of outdated program materials, and a single gender focus. Conclusions: EAAA translates well, with a few adaptations, to a residential campus environment in the U.S. Research is needed to assess program effectiveness in reducing sexual assault.

A Review of Evidence-Based Dating Violence Prevention Programs With Behavioral Change Outcomes for Adolescents and Young Adults.

Adolescent dating violence (DV) is not only a social but also a public health problem, necessitating the development and scale-up of prevention strategies. We conducted a review of the literature to identify adolescent and young adult DV prevention programs that have shown promising behavioral outcomes. The literature search covered articles published from 1996 to 2022 and indexed in Medline, Cochrane, Scopus, PsycINFO, and Embase. The review focused on programs implemented and evaluated in the United States or Canada that included intervention and comparison groups, a baseline assessment, and at least one post-assessment conducted after the intervention exposure. Promising behavioral outcomes were defined as positive, statistically significant differences between intervention and comparison groups with respect to DV perpetration or victimization or bystander behavior in relation to DV. A total of 118 articles were screened by abstract and read in-depth. Eighteen programs that met the inclusion criteria were identified. Of these programs, one showed reductions in DV victimization, six showed reductions in DV perpetration, and nine showed behavioral reductions in both violence perpetration and victimization. The review highlighted that while multiple programs have demonstrated efficacy in preventing or reducing intimate partner violence in North American youth populations, more robust research on the replication of these programs outside researcher-controlled environments is needed. Furthermore, issues with program inclusivity, such as with sex and gender-minority individuals, should be considered in future intervention development and replication research.

Qualitative perspectives on COVID-19, interpersonal violence, and interventions to improve well-being from adolescent girls and young women in Kisumu, Kenya.

Introduction: Adolescent girls and young women (AGYW) face a high burden of gender-based violence (GBV) worldwide. The COVID-19 pandemic and associated policies led to global increases in GBV, decreased access to resources, and disruptions of pathways to care. We aimed to understand the effects of COVID-19 on AGYW affected by GBV in Kisumu, Kenya, as well as to identify possible interventions to mitigate those effects. Methods: Focus group discussions (FGDs) were conducted with AGYW aged 15-25 with a history of exposure to GBV. AGYW were split into age-matched groups; aged 15-19 for younger groups and 19-25 for older groups. Discussions focused on how COVID-19 affected experiences of GBV, access to care services, economic and social outcomes, and opportunities for interventions to mitigate negative impacts of COVID-19 and violence. Results: Five FGDs with 46 AGYW were completed in June-September 2021. AGYW described increases in all types of GBV, particularly sexual abuse and intimate partner violence. Early marriage and subsistence transactional sex also increased. AGYW described violence as both a cause and effect of poor economic, social and health consequences related to the pandemic. Notably, AGYW emphasized stress, lack of mental health support and increased substance use as risk factors for violence, and discussed the deleterious mental health effects of violence-particularly in the wake of disruption of mental health services. COVID-19 disrupted referrals to violence-related services, and reduced access to both medical services and psychosocial services. AGYW believed that interventions focused on improving mental health as well as economic empowerment would be the most feasible and acceptable in mitigating the negative effects of COVID-19 and related exacerbations in violence. Discussion: AGYW reported increases in almost all forms of GBV during the pandemic, with related exacerbation in mental health. Concurrently, AGYW endorsed decreased access to care services. As there is no evidence that violence and mental health challenges will quickly resolve, there is an urgent need to identify and implement interventions to mitigate these negative effects.

Sexual Assault Among Young Adolescents in Informal Settlements in Nairobi, Kenya: Findings from the IMPower and SOS Cluster-Randomized Controlled Trial.

Sexual assault is a global threat to adolescent health, but empowerment self-defense (ESD) interventions have shown promise for prevention. This study evaluated the joint implementation of a girls' ESD program and a concurrent boys' program, implemented via a cluster-randomized controlled trial in informal settlements of Nairobi, Kenya, from January 2016 to October 2018. Schools were randomized to the 12-h intervention or 2-h standard of care. Students were randomly sampled to complete surveys at baseline and again at 24 months post-intervention. A total of 3263 girls, ages 10-14, who completed both baseline and follow-up surveys were analyzed; weights were adjusted for dropout. At follow-up, 5.9% (n = 194/3263) of girls reported having been raped in the prior 12 months. Odds of reporting rape were not significantly different in the intervention versus SOC group (OR: 1.21; 95% CI (0.40, 5.21), p = 0.63). Secondary outcomes, social self-efficacy (OR: 1.08; 95% CI (0.95, 1.22), p = 0.22), emotional self-efficacy (OR 1.07; 95% CI (0.89, 1.29), p = 0.49), and academic self-efficacy (OR: 0.90; 95% CI (0.82, 1.00), p = 0.06) were not significantly different. Exploratory analyses of boys' victimization and perpetration are reported. This study improved on previous ESD studies in this setting with longitudinal follow-up of individuals and independent data collection. This study did not show an effect of the intervention on self-reported rape; findings should be interpreted cautiously due to limitations. Sexual assault rates are high in this young population, underscoring a dire need to implement and rigorously test sexual assault prevention interventions in this setting. The trial was registered with Clinical Trials.gov # NCT02771132. Version 3.1 registered on May 2017, first participant enrolled January 2017.

Symptoms, viral loads, and rebound among COVID-19 outpatients treated with nirmatrelvir/ritonavir compared to propensity score matched untreated individuals.

BACKGROUND: Nirmatrelvir/ritonavir (N/R) reduces severe outcomes among patients with COVID-19; however, rebound after treatment has been reported. We compared symptom and viral dynamics in community-based individuals with COVID-19 who completed N/R and similar untreated individuals. METHODS: We identified symptomatic participants who tested SARS-CoV-2 positive and were N/R eligible from a COVID-19 household transmission study: index cases from ambulatory settings and their households were enrolled, collecting daily symptoms, medication use, and respiratory specimens for quantitative PCR for 10 days, March 2022-May 2023. Participants who completed N/R (treated) were propensity score matched to untreated participants. We compared symptom rebound, viral load (VL) rebound, average daily symptoms, and average daily VL by treatment status measured after N/R completion or, if untreated, seven days after symptom onset. RESULTS: Treated (n=130) and untreated participants (n=241) had similar baseline characteristics. After treatment completion, treated participants had greater occurrence of symptom rebound (32% vs 20%; p=0.009) and VL rebound (27% vs 7%; p<0.001). Average daily symptoms were lower among treated participants compared to untreated participants without symptom rebound (1.0 vs 1.6; p<0.01), but not statistically lower with symptom rebound (3.0 vs 3.4; p=0.5). Treated participants had lower average daily VLs without VL rebound (0.9 vs 2.6; p<0.01), but not statistically lower with VL rebound (4.8 vs 5.1; p=0.7). CONCLUSIONS: Individuals who completed N/R experienced fewer symptoms and lower VL but were more likely to have rebound compared to untreated individuals. Providers should still prescribe N/R, when indicated, and communicate possible increased rebound risk to patients.

Understanding ART Adherence among Adolescent Girls and Young Women in Western Kenya: A Cross-Sectional Study of Barriers and Facilitators.

BACKGROUND: HIV remains a leading cause of death for adolescent girls and young women (AGYW) in sub-Saharan Africa. This population has a high incidence of HIV and other comorbidities, such as experiencing violence, and low antiretroviral therapy (ART) adherence. To reach global HIV goals, data are needed on the specific adherence barriers for AGYW living with HIV, so interventions can be targeted effectively. METHODS: Cross-sectional data were collected at urban and rural health facilities in and around Kisumu County, western Kenya, from January to June 2022, from AGYW 15-24 years of age who were living with HIV. Surveys included questions on intimate partner violence, mental health issues, food security, and orphanhood. Adherence was categorized using viral load testing where available and the Center for Adherence Support Evaluation (CASE) adherence index otherwise. Logistic regression was used to assess associations between potential explanatory variables and adherence. FINDINGS: In total, 309 AGYW participated. AGYW with experiences of emotional violence (Odds Ratio [OR] = 1.94, 95% Confidence Interval [CI] = 1.03-3.66), moderate or severe depression (OR = 3.19, 95% CI = 1.47-6.94), and/or substance use (OR = 2.71, 95% CI = 1.24-5.92) had significantly higher odds of poor adherence when compared to AGYW without these respective experiences. Physical and sexual violence, food insecurity, and orphanhood were not associated with poor adherence in this cohort. INTERPRETATION: Elucidating the risk factors associated with poor adherence among AGYW living with HIV allows us to identify potential targets for future interventions to improve ART adherence and HIV care outcomes. Mental health and violence prevention interventions, including combination interventions, may prove to be promising approaches.

Variation in rates of sexual assault crisis counsellor usage during forensic examination in California: an observational study.

OBJECTIVES: A critical asset to post-assault care of survivors is support from sexual assault crisis counsellors (SACCs). We sought to elucidate variation in implementation between California counties in SACC accompaniment during Sexual Assault Forensic Examination (SAFE). METHODS: SACC attendance data from 2019 was obtained from the California Governor's Office of Emergency Services (CalOES). To assess SACC attendance rates during SAFEs, we requested SAFE quantity data from sheriffs and public health departments, the State Forensic Bureau, and the California Department of Justice (DOJ), but all requests were unanswered or denied. We also sought SAFE data from District Attorneys (DAs) in each county, and received responses from Marin and Contra Costa Counties. To estimate numbers of SAFEs per county, we gathered crime statistics from the Federal Bureau of Investigation's (FBI's) Uniform Crime Reporting Program and OpenJustice, a transparency initiative by the California DOJ. For each data source, we compared SACC attendance to SAFE quantities and incidences of sexual assault statewide. RESULTS: At the state level, data on SACC attendance per CalOES and DOJ archival data on sexual assault were used to approximate relative rates of SACC accompaniment at SAFEs; 83% (30 of 36) of counties had values <50%. The joint sexual assault crisis centre for Contra Costa and Marin Counties reported that 140 SACCs were dispatched in 2019, while DAs in Contra Costa and Marin reported completion of 87 SAFEs in 2019, for a calculated SACC accompaniment rate of 161%. Proxy data sourced from FBI and DOJ crime statistics displayed significant inconsistencies, and DOJ data was internally inconsistent. CONCLUSIONS: SACC accompaniment at SAFEs appears to be low in most California counties, however, limited data accessibility and data discrepancies and inaccuracies (e.g., rates over 100%) prevented reliable determination of SACC accompaniment rates during SAFEs. Substantial improvements in data accuracy and transparency are needed to ensure survivors' adequate access to resources.

Mental health and gender-based violence: An exploration of depression, PTSD, and anxiety among adolescents in Kenyan informal settlements participating in an empowerment intervention.

OBJECTIVE: This study examines the prevalence of depression, anxiety, and post-traumatic stress disorder (PTSD) among adolescents attending schools in several informal settlements of Nairobi, Kenya. Primary aims were estimating prevalence of these mental health conditions, understanding their relationship to gender-based violence (GBV), and assessing changes in response to an empowerment intervention. METHODS: Mental health measures were added to the final data collection point of a two-year randomized controlled trial (RCT) evaluating an empowerment self-defense intervention. Statistical models evaluated how past sexual violence, access to money to pay for a needed hospital visit, alcohol use, and self-efficacy affect both mental health outcomes as well as how the intervention affected female students' mental health. FINDINGS: Population prevalence of mental health conditions for combined male and female adolescents was estimated as: PTSD 12.2% (95% confidence interval 10.5-15.4), depression 9.2% (95% confidence interval 6.6-10.1) and anxiety 17.6% (95% confidence interval 11.2% - 18.7%). Female students who reported rape before and during the study-period reported significantly higher incidence of all mental health outcomes than the study population. No significant differences in outcomes were found between female students in the intervention and standard-of-care (SOC) groups. Prior rape and low ability to pay for a needed hospital visit were associated with higher prevalence of mental health conditions. The female students whose log-PTSD scores were most lowered by the intervention (effects between -0.23 and -0.07) were characterized by high ability to pay for a hospital visit, low agreement with gender normative statements, larger homes, and lower academic self-efficacy. CONCLUSION: These data illustrate a need for research and interventions related to (1) mental health conditions among the young urban poor in low-income settings, and (2) sexual violence as a driver of poor mental health, leading to a myriad of negative long-term outcomes.

Rebuilding child health in South Kivu, Democratic Republic of Congo (DRC): evaluating the Asili social enterprise program.

BACKGROUND: The Democratic Republic of Congo (DRC) has a long history of conflict and ongoing local instability; the eastern provinces, including South Kivu, have been especially affected. Health systems and livelihoods have been undermined, contributing to massive inequities in access to health services and high rates of internal displacement. Asili, an innovative social enterprise program, aimed to provide essential community services and improve the health of under-five children in two South Kivu communities, Mudaka and Panzi, via provision of small-format, franchisable health clinics and clean water services. METHODS: We evaluated utilization and acceptance of Asili services in two study sites, Mudaka and Panzi. Data collected included questions on housing conditions, food security, and at follow up, Asili membership and use, satisfaction with services, and recommendations for improvement. Structured pre- and post-interviews with primary caregivers of families with under-five children were the primary source of data with additional community input collected through focus group discussions. RESULTS: At baseline, we enrolled 843 households in Mudaka and 890 in Panzi. Market segmentation analysis illuminated service usage patterns, showing Asili services were well received overall in both Mudaka and Panzi. Families reporting higher levels of proxy measures of socioeconomic status (SES), such as electricity, land ownership, and education, were more likely to use Asili services, findings that were further supported by focus group discussions among community members. CONCLUSIONS: Rebuilding health infrastructure in post-conflict settings, especially those that continue to be conflict-affected and very low SES, is a challenging prospect. Focus group results for this study highlighted the positive community response to Asili, while also underscoring challenges related to cost of services. Programs may need, in particular, to have different levels of costs for different SES groups. Additionally, longer follow-up periods and increased stability may be needed to assess the potential of social enterprise interventions such as Asili to improve health outcomes, especially in children. TRIAL REGISTRATION: Institutional Review Board approval for this study was obtained at Stanford University (IRB 35216) and the University of Kinshasa, DRC. Further, this study has been registered on Clinicaltrials.gov (record NCT03536286), retrospectively registered as of 4/23/2018.

Youth voices from an informal settlement of Nairobi, Kenya: Engaging adolescent perspectives on violence to inform prevention.

We examined the experiences of violence and self-reported behavioural and community changes as a result of participation in a sexual assault prevention intervention in an informal settlement in Nairobi, Kenya. We conducted longitudinal qualitative in-depth interviews with 20 adolescent girls and 11 adolescent boys at baseline, 12, and 24 months. Analysis was thematic with two investigators coding and reaching consensus about the themes. Participants' ages ranged from 10 to 13 at baseline; girls' mean age was 11.9, boys' mean age was 11.6. Participants reported experiencing high levels of violence at all stages of the study. Most reported feeling more empowered to protect themselves and others from sexual assault because of the intervention. While participants had mixed responses about change in sexual assault incidence, most perceived an improvement in inter-gender relationships after the intervention. Participants at midline and endline cited acquaintances and friends as potential perpetrators of sexual violence more often than at baseline and were more open to reporting violent incidents. The very young adolescents in this setting perceived that this sexual assault prevention intervention led to improvements in gender relations, adolescent girls' empowerment and, recognition of harmful rape myths.Trial registration: ClinicalTrials.gov identifier: NCT02771132.

A Novel Model for Generating Creative, Community-Responsive Interventions to Reduce Gender-Based Violence on College Campuses.

Currently, the most successful prevention interventions against sexual violence (SV) on United States college campuses target modifications at the individual and interpersonal levels. Community-level interventions have been under-developed for college campuses. To address this gap, we employ a citizen science model for understanding campus community factors affecting SV risk. The model, called Our Voice, starts by engaging groups of college students to collect data in their own communities, identifying factors they view as increasing the risk of SV. In facilitated meetings, participants then review and analyze their collective data and use it to generate actionable community-level solutions and advocate for them with local decision-makers. We share findings from a first-generation study of the Our Voice model applied to SV prevention on one college campus, and include recommendations for further research.

The Effect of Combining Business Training, Microfinance, and Support Group Participation on Economic Status and Intimate Partner Violence in an Unplanned Settlement of Nairobi, Kenya.

Intimate partner violence (IPV) has myriad negative health and economic consequences for women and families. We hypothesized that empowering women through a combination of formal business training, microfinance, and IPV support groups would decrease IPV and improve women's economic status. The study included adult female survivors of severe IPV. Women living in Korogocho received the intervention and women in Dandora served as a standard of care (SOC) group, but received the intervention at the end of the follow-up period. Women in the intervention groups (n = 82, SOC group, n = 81) received 8 weeks of business training, assistance creating a business plan, a small initial loan (about US$60), and weekly business and social support meetings. The two primary outcome measures included change in: (a) average daily profit margin, and (b) incidence of severe IPV. Exploratory analysis also looked at incidence of violence against children and women's self-efficacy. Average daily profit margin in the intervention group increased by 351 Kenyan Shillings (about US$3.5) daily (95% CI = [172, 485]). IPV directed against participating women decreased from a baseline of 2.1 to 0.26 incidents, a difference of 1.84 incidents (95% CI = [1.32, 2.36]). Violence against children in the household in the prior 3 months decreased from 1.1 to 0.55 incidents, a difference of 0.55 incidents (95% CI = [0.16, 1.03]). Finally, the intervention appears to have increased self-efficacy scores by 0.42 points (95% CIs 0.13, 0.71). In a low-resource urban environment, employing three complementary interventions resulted in higher daily profit margins and lower IPV in the intervention compared with the SOC group. These data support the notion that employing multiple interventions concomitantly might possess synergistic, beneficial effects, and hold promise to address profound poverty and interrupt the devastating cycle of IPV.

Empirical Insights for Improving Sexual Assault Prevention: Evidence From Baseline Data for a Cluster-Randomized Trial of IMPower and Sources of Strength.

The empirical science of measuring and preventing sexual assault is in its infancy, especially when considering adolescents in developing nations. We analyze pre-intervention data collected in a two-arm cluster-randomized controlled trial of a classroom-based sexual assault prevention program deployed to Class 6 students around Nairobi, Kenya. We estimate that 7.2% of girls were raped in the prior 12 months. We identify school- and individual-level risk factors for rape. We isolate, as much as possible, variation in probability of rape attributable to a subset of these risk factors. We discuss statistical challenges and solutions in each of these domains.

A protocol for a cluster-randomized controlled trial testing an empowerment intervention to prevent sexual assault in upper primary school adolescents in the informal settlements of Nairobi, Kenya.

BACKGROUND: Sexual violence against adolescents is prevalent worldwide and results in significant physical and mental injuries as well as loss of economic and personal potential. Urban informal settlements such as those around Nairobi, Kenya have been shown to have especially high incidences of violence. Research has shown that empowerment interventions for female adolescents can reduce sexual assault. However, these interventions have had limited testing in urban informal settlements, with young adolescents, or in coordination with complementary programs for male adolescents. METHODS/DESIGN: This study was a two-arm, parallel, cluster-randomized trial testing a combination of a previously-tested girls' intervention, IMPower, and a newly revised boys' intervention, Source of Strength. Clusters were defined as schools within the informal settlements; participants were adolescent girls and boys in class 6, generally between the ages of 10-14 at baseline. Data collection began in January 2016 and continued through December 2018. The primary outcome was the change in incidence of self-reported sexual assault among girls from baseline, compared to a life skills standard of care intervention. Secondary outcomes included experiences of physical and emotional violence, as well as determining the effects of the intervention on self-efficacy, self-esteem, and gender attitudes and beliefs, and how those effects led to changes in experience of sexual assault. For the primary outcome and several of the secondary outcomes, we used an intention to treat estimand. DISCUSSION: This was the first randomized controlled trial with longitudinal follow-up of an empowerment self-defense approach to violence prevention for adolescents in informal settlements. The large size and rigorous design supported analysis to understand multiple subgroup experiences in the hypothesized reduction in sexual assault. The study was also unique in its focus on young (10-14 years of age) adolescents and in engaging both boys and girls in separate but coordinated curriculums. The focus on a highly vulnerable and understudied population will make it a significant contribution to the literature on violence prevention. TRIAL REGISTRATION: Clinical Trials.gov # NCT02771132 . Version 3.1 registered May 2017, first participant enrolled January 2017. Retrospectively registered.

Prevalence and risk factors for sexual assault among class 6 female students in unplanned settlements of Nairobi, Kenya: Baseline analysis from the IMPower & Sources of Strength cluster randomized controlled trial.

BACKGROUND: Gender-based violence (GBV) is a crucial global health problem among all age groups, including adolescents. This study describes incidences of GBV, as well as factors associated with sexual assault, among female adolescents in class six living in urban informal settlements in Nairobi, Kenya. METHODS: Study participants were interviewed using a structured survey instrument focusing on experiences of GBV, including emotional, physical, and sexual violence, and corresponding perpetrators, as well as gender attitudes, alcohol use, self-efficacy, and previous sexual experiences. Summary statistics and clustered bootstrap confidence intervals were calculated for social behaviors and violence rates. Stepwise logistic regression identified variables associated with an adolescent's experience of sexual assault. FINDINGS: In this population 7·2% of adolescent girls reported being raped in the prior twelve months, with 11·1% of these rape victims reporting over five experiences. Among the 21·3% who report having had a boyfriend, 38·1% reported emotional, physical, and/or sexual intimate partner violence (IPV). Boyfriends were identified most often as perpetrators, accounting for 46·3% of reported lifetime rapes. Previous experience of physical (p = <0·001) or emotional (p<0·001) IPV and home violence (p<0·001) were risk factors for being raped, while high self-efficacy (p<0·001) was a protective factor. INTERPRETATION: Sexual assault and GBV are major challenges in this highly-disadvantaged population. Novel prevention efforts are needed for this age group, as prevention is often targeted at older adolescents. Prevention efforts should focus on assaults by perpetrators known to adolescents, especially boyfriends, and may need to account for the adolescents' previous experience of, and exposure to, violence.

Protocol Paper: Oral Poliovirus Vaccine Transmissibility in Communities After Cessation of Routine Oral Poliovirus Vaccine Immunization.

Background: We aimed to elucidate household and community-level shedding and transmission of trivalent oral polio vaccine (tOPV) in communities with inactivated polio vaccine (IPV) routine immunization after tOPV is administered during a national health week (NHW). Methods: We conducted a 3-arm, randomized trial with data collected at baseline through 10 weeks post-NHW in households with at least 1 child <5 years old in 3 semi-rural communities in Orizaba, Mexico. Selected communities were geographically isolated but socio-demographically similar. Each community was assigned an oral polio vaccine (OPV) immunization rate: 10, 30, or 70% of participating households. From 2653 households in the 3 communities, ~150 households per community were selected, for 466 in total. Households were randomized as vaccinated or unvaccinated, with only 1 child under 5 in the vaccinated household receiving OPV during the February 2015 NHW. No other community members received OPV during this NHW. Stool samples were collected up to 10 weeks post-vaccination for all members of the 466 study households and were analyzed for the presence of OPV serotypes using a multiplex polymerase chain reaction assay. Results: We will report on the factors associated with, and incidence and duration of, household and community shedding and transmission of OPV. The secondary outcomes will characterize temporal and geospatial OPV serotype shedding patterns. Conclusions: The current global polio eradication plan relies on transitioning away from OPV to IPV. This study contributes to understanding patterns of OPV shedding and transmission dynamics in communities with primary IPV immunity, in order to optimize the reduction of OPV transmission.

OPV Vaccination and Shedding Patterns in Mexican and US Children.

Background: As wild poliovirus is eradicated and countries switch from oral poliovirus vaccine (OPV) to inactivated poliovirus vaccine (IPV) per World Health Organization recommendations, preventing circulation of vaccine-derived poliovirus (cVDPV) is a top priority. Currently, the impact of prior poliovirus vaccination on OPV shedding is not fully understood. Methods: Stool samples from 2 populations were tested for OPV to assess shedding patterns. 505 samples from 43 US children vaccinated with OPV were collected over 42 days post-vaccination. 1,379 samples from 148 Mexican children vaccinated with OPV were collected over 71 days post-vaccination. Prior vaccination history was recorded for both groups. Results: Seventeen (40%) of the US children had never received poliovirus vaccination while the Mexican children had received at least 2 doses of IPV and 116 (78%) had OPV exposure. In total, 84% of US children and 78% of Mexican children shed OPV (P = .44, Fisher exact test), with a mean shedding duration of 17.4 days for US children and 9.3 days for Mexican children (P < .0001, Wilcoxon-Mann Whitney test). Conclusions: Prior vaccination did not affect the likelihood of shedding, as the US and Mexico cohorts had similar shedding proportions. However, prior vaccination affected shedding duration as the Mexican children, who were largely OPV exposed and all of whom had at least 2 IPV vaccinations, shed OPV for half as long as the US cohort. Since different countries maintain different poliovirus vaccination schedules, it is likely that duration of shedding of OPV varies in populations around the world.

Assessing the Risk of Vaccine-derived Outbreaks After Reintroduction of Oral Poliovirus Vaccine in Postcessation Settings.

Background: The Polio Eradication and Endgame Strategic Plan 2013-2018 calls for the gradual withdrawal of oral poliovirus vaccine (OPV) from routine immunization. We aimed to quantify the transmission potential of Sabin strains from OPV when it is reintroduced, accidentally or deliberately, in a community vaccinated with inactivated poliovirus vaccine alone. Methods: We built an individual-based stochastic epidemiological model that allows independent spread of 3 Sabin serotypes and differential transmission rates within versus between households. Model parameters were estimated by fitting to data from a prospective cohort in Mexico. We calculated the effective reproductive number for the Mexico cohort and simulated scenarios of Sabin strain resurgence under postcessation conditions, projecting the risk of prolonged circulation, which could lead to circulating vaccine-derived poliovirus (cVDPV). Results: The estimated effective reproductive number for naturally infected individuals was about 1 for Sabin 2 and Sabin 3 (OPV2 and OPV3) in a postcessation setting. Most transmission events occurred between households. We estimated the probability of circulation for >9 months to be (1) <<1% for all 3 serotypes when 90% of children <5 years of age were vaccinated in a hypothetical outbreak control campaign; (2) 45% and 24% for Sabin 2 and Sabin 3, respectively, when vaccine coverage dropped to 10%; (3) 37% and 8% for Sabin 2 and Sabin 3, respectively, when a single active shedder appeared in a community. Conclusions: Critical factors determining the risk of cVDPV emergence are the scale at which OPV is reintroduced and the between-household transmission rate for poliovirus, with intermediate values posing the greatest risk.

Spatial Analyses of Oral Polio Vaccine Transmission in an Community Vaccinated With Inactivated Polio Vaccine.

Background: Understanding the spatial dynamics of oral polio vaccine (OPV) transmission will improve resource targeting. Mexico provides a natural laboratory, as it uses inactivated polio vaccine routinely as well as OPV bi-annually. Methods: Using geospatial maps, we measured the distance and density of OPV vaccinees' shedding in the areas nearest to unvaccinated households in 3 Mexican villages. Comparison of transmission to unvaccinated households utilized a mixed effects logistic regression with random effects for household and time, adjusted for age, gender, area, and running water. Results: The median distance from an unvaccinated household to its nearest OPV-shedding household was 85 meters (interquartile range, 46-145) and the median number of vaccinees shedding OPV within 200 m was 3 (2-6). Transmission to unvaccinated households occurred by day 1. There was no association (odds ratio [OR] 1.04; 95% credible interval [CrI] 0.92-1.16) between the distance from OPV shedding and the odds of transmission. The number of OPV vaccinees shedding within 200 m came close to a significant association with unvaccinated transmission (OR 0.93; CrI 0.84-1.01), but this was not the case for households 100 or 500 m apart. Results were consistent across the 3 villages. Conclusions: Geospatial analysis did not predict community transmission from vaccinated to unvaccinated households, because OPV use resulted in rapid, low transmission levels. This finding supports the global cessation of OPV.