Estimating population immunity to poliovirus in Lebanon: Results from a seroprevalence survey, 2016.

INTRODUCTION: Circulation of poliovirus in neighboring countries and mass population movement places Lebanon at risk of polio and other vaccine-preventable disease outbreaks. Determining population immunity levels is essential for guiding program planning and implementation of targeted supplementary immunization activities (SIAs) in governorates and subpopulations with low seroprevalence. METHODS: A cross-sectional multi-stage cluster survey was conducted during February-December 2016 in all six governorates of Lebanon adapted from the World Health Organization (WHO) recommended Expanded Progamme on Immunization (EPI) methodology. Sera from selected children aged 12-59 months were tested for poliovirus neutralizing antibodies. RESULTS: Of 2,164 children recruited in this study, 1,893 provided sufficient quantity of serum samples for laboratory testing. Seroprevalence for all three poliovirus serotypes was greater than 90% in all six governorates. Poliovirus vaccine coverage with three or more doses, based on vaccination cards or parental recall, ranged between 54.1% for children aged 36-47 months in the North and 83.5% for children aged 48-59 months in Beirut. CONCLUSION: Immunity to polioviruses was high in Lebanon in 2016 following a series of supplementary immunization activities. It is essential to continue strategies that increase vaccination coverage in order to sustain the considerably high immunity levels and prevent reintroduction and transmission of poliovirus. Educating caregivers and training health care workers on the standardized usage of home-based vaccination records is needed to guarantee the accuracy of records on children's vaccination status.

Factors affecting age-appropriate timeliness of vaccination coverage among children in Lebanon.

Background: The effect of immunization does not only depend on its completeness, but also on its timely administration. Routine childhood vaccinations schedules recommend that children receive the vaccine doses at specific ages. This article attempts to assess timeliness of routine vaccination coverage among a sub-sample of children from a survey conducted in 2016. Methods: This analysis was based on data from a cross-sectional multistage cluster survey conducted between December 2015 and June 2016 among caregivers of children aged 12-59 months in all of Lebanon using a structured survey questionnaire. The analysis used Kaplan-Meier curves and logistic regression to identify the predictors of age-appropriate immunization. Results: Among the 493 randomly selected children, timely administration of the third dose of polio vaccine, diphtheria-tetanus-pertussis (DTP)-containing vaccine and hepatitis B (HepB) vaccine occurred in about one-quarter of children. About two-thirds of children received the second dose of a measles-containing vaccine (MCV) within the age interval recommended by the Expanded Programme on Immunization (EPI). Several factors including socio-demographic, knowledge, beliefs and practices were found to be associated with age-appropriate vaccination; however, this association differed between the types and doses of vaccine. Important factors associated with timely vaccination included being Lebanese as opposed to Syrian and being born in a hospital for hepatitis B birth dose; believing that vaccination status was up-to-date was related to untimely vaccination. Conclusions: The results suggest that there is reason for concern over the timeliness of vaccination in Lebanon. Special efforts need to be directed towards the inclusion of timeliness of vaccination as another indicator of the performance of the EPI in Lebanon.

A unique alpha dosimetry technique using Gafchromic EBT3(®) film and feasibility study for an activity calibrator for alpha-emitting radiopharmaceuticals.

OBJECTIVE: To develop an alpha dosimetry technique for activity calibration of alpha-emitting radiopharmaceuticals using the Gafchromic(®) EBT3 (Gaf-EBT3) radiochromic film (International Speciality product, Wayne, NJ). METHODS: The Gaf-EBT3 has a tissue equivalent radiosensitive layer (approximately 28 µm) sandwiched between two 100-µm thick polyester sheaths, thereby making it insensitive to alpha particles. We have split a Gaf-EBT3 sheet using a surgical scalpel to remove one of the polyester protective layers and covered the radiosensitive layer with thin Mylar(®) foil (Goodfellow Cambridge Limited, Huntingdon, UK) (2.5 µm). Small pieces of modified film were exposed at contact with a 560-Bq thin (241)Am source for 5, 10, 24 and 94 h. The optical density of the films was evaluated using an optical densitometer. The alpha energy spectra of the (241)Am source were recorded using a Si(Li) surface barrier detector. RESULTS: Time-integrated specific alpha surface activity (kBq cm(-2) h) was represented as a function of optical density. CONCLUSION: By removing one of the 100 µm thick polyester protective layers, the authors have modified the Gaf-EBT3 film to a sensitive alpha dosemeter. The calibration function relevant to a (241)Am reference source was evaluated from the optical densities of the dosemeter foils. Furthermore, calibration functions for important alpha emitters such as (223)Ra, (225)Ac or (210)Bi were parameterized from the (241)Am reference data. ADVANCES IN KNOWLEDGE: The authors have developed and tested the principle of a clinical alpha dosemeter using Gaf-EBT3 radiochromic films originally developed for photon dosimetry. This novel, user-friendly technique could be implemented in quality assurance and calibration procedures of important alpha-emitting radiopharmaceuticals prior to their clinical applications.