The current polio epidemiology in Pakistan poses a unique challenge for global eradication as the country is affected by ongoing endemic poliovirus transmission. Across the country, 40 union councils (UCs) which serve as core reservoirs for poliovirus with continuous incidences of polio cases are categorized as super-high-risk union councils (SHRUCs). A cross-sectional survey was conducted in 39 SHRUCs using a two-stage stratified cluster sampling technique. 6,976 children aged 12-23 months were covered. A structured questionnaire was used for data collection. Data were analyzed using STATA version 17. Based on both vaccination records and recall, 48.3% of children were fully-, 35.4 % were partially-, and 16.3% were non-vaccinated in the SHRUC districts. A child is considered fully vaccinated when h/she completed vaccination for BCG, OPV0, OPV 1-3, Penta 1-3, PCV 1-3, IPV, and MCV1. Vaccination cards were seen for over half of the children in the SHRUC districts of Khyber Pakhtunkhwa (KP) and the majority of the SHRUC districts in Sindh, except for the SHRUC district of Malir the districts of Balochistan. Results for polio vacancies show that 60.9% of children from the SHRUC districts were vaccinated with at least three doses of OPV and one dose of IPV, while 20.4% were vaccinated with any OPV doses or IPV and 18.7% of children did not receive any polio vaccines. The dropout rate between vaccine visits was higher than the WHO-recommended cutoff point of 10% for all vaccine doses in the SHRUC districts. The likelihood of being fully vaccinated was higher among the children of educated parents. Full vaccination was found significant among the children of any SHRUC districts compared to district Killa Abdullah. Context-specific strategies with more focus on community engagement and targeted mobilization, along with robust monitoring mechanisms, would help address the underlying challenges of under-immunization in the SHRUCs.

In 2015, the World Health Organization substantially revised its guidance for vaccination coverage cluster surveys (revisions were finalized in 2018) and has since developed a set of accompanying resources, including definitions for standardized coverage indicators and software (named the Vaccination Coverage Quality Indicators—VCQI) to calculate them.–The current WHO vaccination coverage survey manual was used to design and conduct two nationally representative vaccination coverage surveys in Nigeria–one to assess routine immunization and one to measure post-measles campaign coverage. The primary analysis for both surveys was conducted using VCQI. In this paper, we describe those surveys and highlight some of the analyses that are facilitated by the new resources. In addition to calculating coverage of each vaccine-dose by age group, VCQI analyses provide insight into several indicators of program quality such as crude coverage versus valid doses, vaccination timeliness, missed opportunities for simultaneous vaccination, and, where relevant, vaccination campaign coverage stratified by several parameters, including the number of previous doses received. The VCQI software furnishes several helpful ways to visualize survey results. We show that routine coverage of all vaccines is far below targets in Nigeria and especially low in northeast and northwest zones, which also have highest rates of dropout and missed opportunities for vaccination. Coverage in the 2017 measles campaign was higher and showed less geospatial variation than routine coverage. Nonetheless, substantial improvement in both routine program performance and campaign implementation will be needed to achieve disease control goals.

One important strategy to increase vaccination coverage is to minimize missed opportunities for vaccination. Missed opportunities for simultaneous vaccination (MOSV) occur when a child receives one or more vaccines but not all those for which they are eligible at a given visit. Household surveys that record children’s vaccination dates can be used to quantify occurrence of MOSVs and their impact on achievable vaccination coverage. We recently automated some MOSV analyses in the World Health Organization’s freely available software: Vaccination Coverage Quality Indicators (VCQI) making it straightforward to study MOSVs for any Demographic & Health Survey (DHS), Multi-Indicator Cluster Survey (MICS), or Expanded Programme on Immunization (EPI) survey. This paper uses VCQI to analyze MOSVs for basic vaccine doses among children aged 12–23 months in four rounds of DHS in Colombia (1995, 2000, 2005, and 2010) and five rounds of DHS in Nigeria (1999, 2003, 2008, 2013, and 2018). Outcomes include percent of vaccination visits MOSVs occurred, percent of children who experienced MOSVs, percent of MOSVs that remained uncorrected (that is, the missed vaccine had still not been received at the time of the survey), and the distribution of time-to-correction for children who received the MOSV dose at a later visit.

Pilot testing is crucial when preparing any community-based vaccination coverage survey. In this paper, we use the term pilot test to mean informative work conducted before a survey protocol has been finalized for the purpose of guiding decisions about how the work will be conducted. We summarize findings from seven pilot tests and provide practical guidance for piloting similar studies. We selected these particular pilots because they are excellent models of preliminary efforts that informed the refinement of data collection protocols and instruments. We recommend survey coordinators devote time and budget to identify aspects of the protocol where testing could mitigate project risk and ensure timely assessment yields, credible estimates of vaccination coverage and related indicators. We list specific items that may benefit from pilot work and provide guidance on how to prioritize what to pilot test when resources are limited.

This paper describes the design and methods of a serosurvey conducted in Somalia in 2021. The study had several concurrent aims: a) to estimate seroprevalence of antibodies to SARS-CoV-2, b) to obtain age-specific data on susceptibility to poliovirus, measles, rubella, diphtheria, and tetanus; and c) to estimate seroprevalence of pathogens causing malaria and neglected tropical diseases. Participants were recruited from persons seeking care at government health facilities as well as friends and family members who accompanied those seeking care. Respondents answered interview questions to establish their demographic profile, their COVID-19 exposure and experience, and, for children, their routine immunization status. Each participant contributed a sample of blood for serum or dried blood spots. Serum samples were analyzed in Somalia for SARS-CoV-2 and dried blood spots were analyzed at the US Centers for Disease Control and Prevention (US CDC) for the other diseases and antigens of interest. This manuscript describes the study design, logistics, laboratory methods, and data management steps used to compile the study dataset. Study results will be reported in a series of manuscripts to follow.

Since the 1970s the World Health Organization (WHO) has promoted household surveys with a cluster sample design as an important method to estimate vaccination coverage in low- and middle-income countries. When calculating the survey sample size, planners begin with an educated guess at the outcome proportion and a target precision for the estimate and calculate an effective sample size that would achieve that precision if using a simple random sample. Then they account for correlated outcomes in the cluster sample using an estimated design effect (DEFF) that depends, among other things, on the unknown rate of homogeneity of the outcome as parameterized with an intracluster correlation coefficient (ICC). From the 1970s until 2015, WHO materials suggested that vaccination coverage surveys could be self-weighting and their ICCs would rarely exceed 1/6 or 0.1667. Recommendations drafted in 2015 and finalized in 2018 suggested using a probability sample with survey weights that vary and using a more conservative ICC value of 1/3 = 0.3333 for routine immunization surveys if there was no recent evidence-based estimate available. In this manuscript, we examine variability in survey weights and ICCs for 18 binary outcomes from two recent nationally representative vaccination coverage surveys in Pakistan with 152 districts serving as strata in the sample design, and either 49 or 64 clusters per stratum. The observed values of these parameters are summarized and used to (i) help planners use appropriately small values of ICC when the outcome is expected to have extreme values and (ii) suggest how WHO recommendations on ICC and weights might be refined in a forthcoming update.