National Weekly SARS-CoV-2 RT-PCR Screening of All Workers in Long-Term Care Facilities Associated with Decrease in Resident Mortality Rate.

INTRODUCTION: Outbreaks of COVID-19 in long-term care facilities (LTCFs) have resulted mainly from disease transmission by asymptomatic health care workers. This study examines whether routine screening tests carried out on health care workers can help in reducing COVID-19 outbreaks, morbidity, and mortality of LTCF residents. METHODS: The study followed a weekly, nationwide, government-funded screening program of LTCF personnel for SARS-CoV-2, by using reverse transcription polymerase chain reaction as the main testing technology. It included all residents and employees in Israeli LTCFs who were screened weekly during the second wave of COVID-19, during the period of time between July 13, 2020, and November 21, 2020. RESULTS: During the study period, 1,107 LTCFs were screened on a weekly basis, including 62,159 HCWs and 100,046 residents. The program screened a median of 55,282 (range 16,249, min 45,910, max 62,159) employees per week, 0.05-1.5% of which were positive for SARS-CoV-2. LTCF mortality in the first wave accounted for 45.3% of all COVID-19 deaths recorded nationally (252 of 556), and in the second wave, this ratio was reduced to 30.3% (709 of 2,337) representing a reduction of 33.8% in expected mortality (p < 0.001). A significant reduction was detected also in hospitalization rate (13.59 vs. 11.41%, p < 0.001) and elder (≥75 years old) mortality rate (52.89 vs. 41.42%, p < 0.001). 214 outbreaks in the second wave were avoided by early identification of SARS-CoV-2 positive HCWs and successful prevention of subsequent infections in the facility. CONCLUSION: Routine weekly SARS-CoV-2 RT-PCR testing of LTCF employees was associated with reduced national LTCF residents' hospitalizations and mortality rate.

Effectiveness of BNT162b2 mRNA Coronavirus Disease 2019 (COVID-19) Vaccine Against Acquisition of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Among Healthcare Workers in Long-Term Care Facilities: A Prospective Cohort Study.

BACKGROUND: We assessed vaccine effectiveness (VE) of BNT162b2 mRNA coronavirus disease 2019 (COVID-19) vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) acquisition among healthcare workers (HCWs) of long-term care facilities (LTCFs). METHODS: This prospective study, in the framework of the "Senior Shield" program in Israel, included routine weekly nasopharyngeal SARS-CoV-2 RT-PCR testing from all LTCF HCWs since July 2020. All residents and 75% of HCWs were immunized between December 2020 and January 2021. The analysis was limited to HCWs adhering to routine testing. Fully vaccinated (14+ days after second dose; n = 6960) and unvaccinated (n = 2202) HCWs were simultaneously followed until SARS-CoV-2 acquisition or end of follow-up, 11 April 2021. Hazard ratios (HRs) for vaccination versus no vaccination were calculated (Cox proportional hazards regression models, adjusting for sociodemographics and residential-area COVID-19 incidence). VE was calculated as (1- HR) × 100. RT-PCR cycle threshold (Ct) values were compared between vaccinated and unvaccinated HCWs. RESULTS: At >14 days post-second dose, 40 vaccinated HCWs acquired SARS-CoV-2 (median follow-up, 66 days; cumulative incidence, 0.6%) versus 84 unvaccinated HCWs (median follow-up, 43 days; cumulative incidence, 5.1%) (HR, .11; 95% CI, .07-.17; unadjusted VE, 89%; 95% CI, 83-93%). Adjusted VE >7 and >14 days post-second dose were similar. The median PCR Ct targeting the ORF1ab gene among 20 vaccinated and 40 unvaccinated HCWs was 32.0 versus 26.7, respectively (P value  = .008). CONCLUSIONS: VE following 2 doses of BNT162b2 against SARS-CoV-2 acquisition in LTCF HCWs was high. The lower viral loads among SARS-CoV-2-positive HCWs suggest further reduction in transmission.

Pediatric Hospitalizations After School Reopening During the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Alpha (B.1.1.7) Variant Spread: A Multicenter Cross-sectional Study in Israel.

This multicenter, cross-sectional study provides evidence on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-associated emergency department visits and hospitalizations in pediatric wards and intensive care units after school reopening during the SARS-CoV-2 Alpha (B.1.1.7) variant spread in Israel. Study findings suggest that school reopening was not followed by an increase in SARS-CoV-2-related pediatric morbidity.

Changes in General and Virus-Specific Anxiety During the Spread of COVID-19 in Israel: A 7-Wave Longitudinal Study.

We compared 3 hypothetical trajectories of change in both general and coronavirus disease 2019 (COVID-19)-specific anxiety during the first wave of the spread in the state of Israel: panic (very high anxiety, either from the outset or rapidly increasing), complacency (stable and low anxiety), and threat-sensitive (a moderate, linear increase compatible with the increase in threat). A representative sample of 1,018 Jewish-Israeli adults was recruited online. A baseline assessment commenced 2 days prior to the identification of the first case, followed by 6 weekly assessments. Latent mixture modeling analyses revealed the presence of 3 trajectories: 1) "threat-sensitivity" (29% and 66%, for general and virus-specific anxiety, respectively), 2) panic (12% and 25%), and 3) complacency (29% and 9%). For general anxiety only, a fourth class representing a stable mid-level anxiety was identified ("balanced": 30%). For general anxiety, women and the initially anxious-both generally and specifically from the spread of the virus-were more likely to belong to the panic class. Men and older participants were more likely to belong to the complacency class. Findings indicate a marked heterogeneity in anxiety responses to the first wave of the spread of COVID-19, including a large group evincing a "balanced" response.

A Non-Randomized Controlled Trial for Reducing Postpartum Depression in Low-Income Minority Women at Community-Based Women's Health Clinics.

OBJECTIVE: To analyze an intervention that delivered tailored clinic staff training on postpartum depression (PPD) followed by awareness raising and social support aimed at lowering PPD among low-income Bedouin women in southern Israel. METHODS: We conducted a non-randomized controlled trial at two women's health clinics. The study included 332 of the 384 eligible women recruited at baseline (intervention = 169, control = 163), who completed two face-to-face interviews, one at 26-38 weeks of pregnancy (Time 1) and one 2-4 months postpartum (Time 2). PPD was measured by the Edinburgh Postnatal Depression Scale (EPDS) and dichotomized using a ≥ 10 score cutoff. We calculated EPDS change (rate difference of dichotomous EPDS from Time 1 to Time 2) (no change, positive change, or negative change), and compared EPDS changes in a control clinic vs. an intervention clinic. RESULTS: The intervention group showed a greater decrease in dichotomous EPDS ≥ 10 between times 1 and 2 (38.5% to 17.2%) than the control group (31.9% to 29.4%, PV = 0.008). Multinomial logistic regression showed that high PPD awareness significantly contributed to positive EPDS change in the intervention group (PV = 0.003) and high social support significantly protected against negative EPDS change in both groups, intervention (PV = 0.001) and control (PV = 0.003). CONCLUSIONS: In low-income women, an intervention focusing on increasing PPD awareness and social support following staff training was associated with reduced EPDS and positive EPDS change following the intervention. Similar interventions should be implemented in women's clinics during pregnancy. CLINICAL TRIAL REGISTRY: ClinicalTrials.gov NCT02862444.

Associations Between Prenatal Exposure to Air Pollution and Congenital Hypothyroidism.

Adequate thyroid hormone availability is required for normal brain development. Studies have found associations between prenatal exposure to air pollutants and thyroid hormones in pregnant women and newborns. We aimed to examine associations of trimester-specific residential exposure to common air pollutants with congenital hypothyroidism (CHT). All term infants born in Israel during 2009-2015 were eligible for inclusion. We used data on CHT from the national neonatal screening lab of Israel, and exposure data from spatiotemporal air pollution models. We used multivariable logistic regression models to estimate associations of exposures with CHT, adjusting for ethnicity, socioeconomic status, geographical area, conception season, conception year, gestational age, birth weight, and child sex. To assess residual confounding, we used postnatal exposures to the same pollutants as negative controls. The study population included 696,461 neonates. We found a positive association between third-trimester nitrogen oxide exposure and CHT (per interquartile-range change, odds ratio = 1.23, 95% confidence interval: 1.08, 1.41) and a similar association for nitrogen dioxide. There was no evidence of residual confounding or bias by correlation among exposure periods for these associations.

Epidemiology of the silent polio outbreak in Rahat, Israel, based on modeling of environmental surveillance data.

Israel experienced an outbreak of wild poliovirus type 1 (WPV1) in 2013-2014, detected through environmental surveillance of the sewage system. No cases of acute flaccid paralysis were reported, and the epidemic subsided after a bivalent oral polio vaccination (bOPV) campaign. As we approach global eradication, polio will increasingly be detected only through environmental surveillance. We developed a framework to convert quantitative polymerase chain reaction (qPCR) cycle threshold data into scaled WPV1 and OPV1 concentrations for inference within a deterministic, compartmental infectious disease transmission model. We used this approach to estimate the epidemic curve and transmission dynamics, as well as assess alternate vaccination scenarios. Our analysis estimates the outbreak peaked in late June, much earlier than previous estimates derived from analysis of stool samples, although the exact epidemic trajectory remains uncertain. We estimate the basic reproduction number was 1.62 (95% CI 1.04-2.02). Model estimates indicate that 59% (95% CI 9-77%) of susceptible individuals (primarily children under 10 years old) were infected with WPV1 over a little more than six months, mostly before the vaccination campaign onset, and that the vaccination campaign averted 10% (95% CI 1-24%) of WPV1 infections. As we approach global polio eradication, environmental monitoring with qPCR can be used as a highly sensitive method to enhance disease surveillance. Our analytic approach brings public health relevance to environmental data that, if systematically collected, can guide eradication efforts.

Lower rates of neural tube defects in Israel following folic acid supplementation policy.

Neural tube defects (NTDs) are common and disabling congenital malformations that remain a public health challenge despite prevention efforts. In 2000, The Israeli Ministry of Health published recommendations on daily folic acid (FA) supplementation for women of reproductive age and established a national NTD registry. This study aims to evaluate the long-term impact of the FA supplementation policy on NTD rates in Israel and the need for further intervention. In this descriptive report, we present the rate of NTD-affected pregnancies recorded in the registry between 2000 and 2012, their subtype (anencephaly, spina bifida or other), outcome (live birth, stillbirth or pregnancy termination), ethnic group (Jewish, Bedouin and non-Bedouin Muslim) and years of maternal education. The final analysis included 2374 NTD cases reported between 2000 and 2012, compared with 1,668,073 live births. During this period NTD rates decreased from 20.3 to 11.2 cases per 10,000 live births, a 45% reduction. Reductions were seen in rates of spina bifida, anencephaly and encephalocele. NTD rates decreased in all pregnancy outcomes and in all ethnic groups, though rates among Bedouins remain high. Women with higher levels of education tended to have lower NTD rates, and were more prone to choose termination of an affected pregnancy. Following the institution of FA supplementation in Israel, a substantial reduction was seen in NTD rates. Nonetheless, Israeli NTD rates remain higher than in other developed countries. FA interventions should continue to be vigorously implemented, especially in vulnerable populations. The global success of mandatory fortification of grain strongly advocates its consideration in Israel.

Unconventional oil and gas development and health outcomes: A scoping review of the epidemiological research.

BACKGROUND: Hydraulic fracturing together with directional and horizontal well drilling (unconventional oil and gas (UOG) development) has increased substantially over the last decade. UOG development is a complex process presenting many potential environmental health hazards, raising serious public concern. AIM: To conduct a scoping review to assess what is known about the human health outcomes associated with exposure to UOG development. METHODS: We performed a literature search in MEDLINE and SCOPUS for epidemiological studies of exposure to UOG development and verified human health outcomes published through August 15, 2019. For each eligible study we extracted data on the study design, study population, health outcomes, exposure assessment approach, statistical methodology, and potential confounders. We reviewed the articles based on categories of health outcomes. RESULTS: We identified 806 published articles, most of which were published during the last three years. After screening, 40 peer-reviewed articles were selected for full text evaluation and of these, 29 articles met our inclusion criteria. Studies evaluated pregnancy outcomes, cancer incidence, hospitalizations, asthma exacerbations, sexually transmitted diseases, and injuries or mortality from traffic accidents. Our review found that 25 of the 29 studies reported at least one statistically significant association between the UOG exposure metric and an adverse health outcome. The most commonly studied endpoint was adverse birth outcomes, particularly preterm deliveries and low birth weight. Few studies evaluated the mediating pathways that may underpin these associations, highlighting a clear need for research on the potential exposure pathways and mechanisms underlying observed relationships. CONCLUSIONS: This review highlights the heterogeneity among studies with respect to study design, outcome of interest, and exposure assessment methodology. Though replication in other populations is important, current research points to a growing body of evidence of health problems in communities living near UOG sites.

Traffic-related Air Pollution and Pregnancy Loss.

BACKGROUND: Traffic-related air pollution has been linked to multiple adverse pregnancy outcomes. However, few studies have examined pregnancy loss, targeting losses identified by hospital records, a large limitation as it does not capture events not reported to the medical system. METHODS: We used a novel variation of the time-series design to determine the association, and identify the critical window of vulnerability, between week-to-week traffic-related air pollution and conceptions resulting in live births, using nitrogen dioxide (NO2) as a traffic emissions tracer. We used information from all live births recorded at Beth Israel Deaconess Medical Center in Boston, MA (2000-2013) and all live births in Tel Aviv District, Israel (2010-2013). RESULTS: In Boston (68,969 live births), the strongest association was during the 15th week of gestation; for every 10 ppb of NO2 increase during that week, we observed a lower rate of live births (rate ratio [RR] = 0.87; 95% confidence interval [CI], 0.78, 0.97), using live birth-identified conceptions to infer pregnancy losses. In the Tel Aviv District (95,053 live births), the strongest estimate was during the 16th gestational week gestation (RR = 0.82; 95% CI, 0.76, 0.90 per 10 ppb of NO2). CONCLUSIONS: Using weekly conceptions ending in live birth rather than identified pregnancy losses, we comprehensively analyzed the relationship between air pollution and all pregnancy loss throughout gestation. The observed results, with remarkable similarity in two independent locations, suggest that higher traffic-related air pollution levels are associated with pregnancy loss, with strongest estimates between the 10th and 20th gestational weeks.

Outbreak of human leptospirosis linked to contaminated water bodies in Northern Israel, June to August 2018.

We report preliminary findings of a large outbreak of human leptospirosis with 36 confirmed/probable and 583 suspected cases from June-August 2018, linked to contaminated water bodies in Northern Israel. There was a travel-associated case in Germany; additional cases are being investigated in other countries. The presumed chain of transmission, implicating wild boar and cattle, raises multiple challenges for risk assessment, risk management and risk communication currently being addressed by a public health response team.

Medical condition and care of undocumented migrants in ambulatory clinics in Tel Aviv, Israel: assessing unmet needs.

BACKGROUND: Approximately 150,000 undocumented migrants (UM) who are medically uninsured reside in Israel, including ~50,000 originating from the horn of Africa (MHA). Free medical-care is provided by two walk-in clinics in Tel-Aviv. This study aims to compare the medical complaints of UM from different origins, define their community health needs and assess gaps between medical needs and available services. METHODS: This cross-sectional study included a random sample of 610 UM aged 18-64 years, who were treated in these community clinics between 2008 and 2011. The study compared UM who had complex medical conditions which necessitated referral to more equipped medical settings with UM having mild/simple medical conditions, who were treated at the clinics. RESULTS: MHA were younger, unemployed and more commonly males compared with UM originating from other countries. MHA also had longer referral-delays and visited the clinics less frequently. UM with complex medical conditions were more commonly females, had chronic diseases and demonstrated longer referral-delays than those who had mild/simple medical conditions. The latter more commonly presented with complained of respiratory, muscular and skeletal discomfort. In multivariate analysis, the variables which predicted complex medical conditions included female gender, chronic illnes and self-referral to the clinics. CONCLUSIONS: The ambulatory clinics were capable of responding to mild/simple medical conditions. Yet, the health needs of women and migrants suffering from complex medical conditions and chronic diseases necessitated referrals to secondary/tertiary medical settings, while jeopardizing the continuity of care. The health gaps can be addressed by a more holistic social approach, which includes integration of UM in universal health insurance.

Ongoing hepatitis A among men who have sex with men (MSM) linked to outbreaks in Europe in Tel Aviv area, Israel, December 2016 - June 2017.

Between December 2016 and June 2017, 19 Hepatitis A virus (HAV)-positive cases, 17 of which were among men who have sex with men (MSM) were identified in the Tel Aviv area. Seven of the 15 sewage samples collected between January and June 2017 were also HAV-positive. All sequences clustered with two of the three strains identified in the current European HAV outbreak. We demonstrate that despite an efficient vaccination programme, HAV can still be transmitted to an unvaccinated high-risk population.

[INFLUENZA VACCINATION AMONG HEALTHCARE WORKERS - THE DATA AND THE DUTY].

INTRODUCTION: Seasonal influenza is a significant disease affecting public health due to substantial morbidity and mortality and a high economic burden. in view of its high propensity for genetic mutations, the virus can easily evade preexisting immunity acquired from prior exposure to it, thereby causing severe seasonal epidemics. Influenza vaccination has been shown to be safe and effective. In many countries, including Israel, it is recommended to all members of the population aged 6 months and older, especially those with a higher risk of developing severe complications. Its adverse effects are mostly minimal, local and systemic. No evidence-based relationship between the vaccination and neurological syndromes was found. Infected health care workers (HCWs) may transmit influenza to patients, many of whom have serious underlying conditions that increase their risk of complications. Therefore, influenza vaccination among HCWs is recommended in the United States and in >40 other countries including Israel. In spite of that, the vaccination coverage rates remain low in Israel and in many countries. The reasons include low levels of awareness to the disease severity, to the safety and effectiveness of the vaccine and low levels of trust in authorities. The effectiveness and safety of the vaccine in preventing influenza among the recipients is well documented. High quality evidence on the effectiveness of the vaccine in preventing the disease among patients and family members of HCWs who receive the vaccine is limited. However, combining the existing evidence and the clear biological plausibility lead to the conclusion that the recommendation for vaccinating health care workers against influenza to protect patients is a well-based policy. This is the policy of the WHO, CDC and health authorities in most developed countries. The Ministry of Health in Israel will continue to promote programs to increase vaccine compliance rates among HCWs and to define the uptake of vaccination as a moral duty.

Modeling the spread of polio in an IPV-vaccinated population: lessons learned from the 2013 silent outbreak in southern Israel.

BACKGROUND: Polio eradication is an extraordinary globally coordinated health program in terms of its magnitude and reach, leading to the elimination of wild poliovirus (WPV) in most parts of the world. In 2013, a silent outbreak of WPV was detected in Israel, a country using an inactivated polio vaccine (IPV) exclusively since 2005. The outbreak was detected using environmental surveillance (ES) of sewage reservoirs. Stool surveys indicated the outbreak to be restricted mainly to children under the age of 10 in the Bedouin population of southern Israel. In order to curtail the outbreak, a nationwide vaccination campaign using oral polio vaccine (OPV) was conducted, targeting all children under 10. METHODS: A transmission model, fitted to the results of the stool surveys, with additional conditions set by the ES measurements, was used to evaluate the prevalence of WPV in Bedouin children and the effectiveness of the vaccination campaign. Employing the parameter estimates of the model fitting, the model was used to investigate the effect of alternative timings, coverages and dosages of the OPV campaign on the outcome of the outbreak. RESULTS: The mean estimate for the mean reproductive number was 1.77 (95 % credible interval, 1.46-2.30). With seasonal variation, the reproductive number maximum range was between zero and six. The mean estimate for the mean infectious periods was 16.8 (8.6-24.9) days. The modeling indicates the OPV campaign was effective in curtailing the outbreak. The mean estimate for the attack rate in Bedouin children under 10 at the end of 2014 was 42 % (22-65 %), whereas without the campaign the mean projected attack rate was 57 % (35-74 %). The campaign also likely shortened the duration of the outbreak by a mean estimate of 309 (2-846) days. A faster initiation of the OPV campaign could have reduced the incidence of WPV even if a lower coverage was reached, at the risk of prolonging the outbreak. CONCLUSIONS: OPV campaigns are essential for interrupting WPV transmission, even in a developed country setting with a high coverage of IPV. In this setting, establishing ES of WPV circulation is particularly crucial for early detection and containment of an outbreak.

The Israeli national population program of genetic carrier screening for reproductive purposes.

PURPOSE: The Israeli population genetic screening program for reproductive purposes, launched in January 2013, includes all known, nationally frequent severe diseases (carrier frequency 1:60 and/or disease frequency 1 in 15,000 live births). The carrier screening program is free of charge and offers testing for cystic fibrosis, fragile X syndrome, and spinal muscular atrophy for nearly the entire population, according to disease frequency among the different groups within the population. We report the results of the first year of the program. METHODS: Data on the tests performed over a 12-month period were collected from laboratories nationwide. RESULTS: More than 62,000 individuals were examined. The carrier frequency was within the expected range for most of the diseases. The few exceptions included lower carrier rates for cystic fibrosis among Muslim Arabs (1:236) and Druze (1:1,021) and Niemann-Pick type A among Muslim Arabs in a delineated region of Israel (1:229). CONCLUSION: The national population genetic carrier screening is aimed toward providing couples with knowledge of the existing options for the prevention of serious genetic conditions when it is relevant for them. It is still too early to determine whether this aim has been achieved.

Child Health Care in Israel.

Israel is a relatively rapidly growing country with a high fertility rate and a young population. These data emphasize the importance of an efficient and appropriate pediatric service for its population. Although the pediatric service in Israel has attained several achievements, such as a relatively low infant mortality, high vaccination rates, and a primary care service that is mainly based on licensed pediatricians, several challenges, such as overcoming inequalities in health care and health indices between different regions and different populations within the country and the provision of a more organized mental and dental health care service to children, need to be addressed.

Ethnicity and immunization coverage among schools in Israel.

OBJECTIVE: Recent years have seen a global trend of declining immunization rates of recommended vaccines that is more pronounced among school-age children. Ethnic disparities in child immunization rates have been reported in several countries. We investigated an effect of ethnicity on the vaccination rates of immunizations routinely administered within schools in Israel. DESIGN: Data were collected from the Ministry of Health database regarding immunization coverage for all registered Israeli schools (3736) in the years 2009-2011. Negative binomial regression was used to assess the association between school ethnicity and immunization coverage while controlling for school characteristics. RESULTS: The lowest immunization coverage was found in Bedouin schools (median values of 75.1%, 81.5% and 0% for the first, second and eighth grades, respectively) in 2011. During this year, vaccination coverage in the first and second grades in Jewish schools was 1.51 and 1.35 times higher, respectively, compared to Bedouin schools. In the years 2009 and 2010, no significant increase in risk for lower vaccination rate was observed in Bedouin schools, and children in Arab and Druze schools were more likely to have been vaccinated. CONCLUSION: The lower vaccination refusal rate found in Bedouin schools supports the hypothesis that difficulties related to accessibility constitute the main problem rather than noncompliance with the recommended vaccination protocol for school-age children, featuring higher socio-economic status groups. Our study emphasizes the importance of identifying, beyond the national-level data, subpopulation groups at risk for non-vaccination. This knowledge is essential to administrative-level policy-makers for the allocation of resources and the planning of intervention programs.

Modeling options to manage type 1 wild poliovirus imported into Israel in 2013.

BACKGROUND: After 25 years without poliomyelitis cases caused by circulating wild poliovirus (WPV) in Israel, sewage sampling detected WPV type 1 (WPV1) in April 2013, despite high vaccination coverage with only inactivated poliovirus vaccine (IPV) since 2005. METHODS: We used a differential equation-based model to simulate the dynamics of poliovirus transmission and population immunity in Israel due to past exposure to WPV and use of oral poliovirus vaccine (OPV) in addition to IPV. We explored the influences of various immunization options to stop imported WPV1 circulation in Israel. RESULTS: We successfully modeled the potential for WPVs to circulate without detected cases in Israel. Maintaining a sequential IPV/OPV schedule instead of switching to an IPV-only schedule in 2005 would have kept population immunity high enough in Israel to prevent WPV1 circulation. The Israeli response to WPV1 detection prevented paralytic cases; a more rapid response might have interrupted transmission more quickly. CONCLUSIONS: IPV-based protection alone might not provide sufficient population immunity to prevent poliovirus transmission after an importation. As countries transition to IPV in immunization schedules, they may need to actively manage population immunity and consider continued use of OPV, to avoid the potential circulation of imported live polioviruses before globally coordinated cessation of OPV use.