Progress. The interprogrammatic group consisted of delegates from the Ministry of Public Health and Social Welfare, the LCSP, the Expanded Program on Immunization, the child and adolescent health programs, and the indigenous health program, as well as delegates from the health regions where the survey was conducted. Field implementation of a school-based serosurvey concluded in February 2020, laboratory analysis of samples was completed in 2021, and the preliminary analysis of the survey results was completed in 2022. The study population included 1 200 children (6-15 years old) from schools in the Chaco region. Fourteen antigens were analyzed for the study to obtain data on ten diseases (Table 2).
Challenges. Fieldwork was prolonged due to flooding and difficulties in accessing the study areas. A total of 1 104 samples were collected. Regarding laboratory analysis of specimens at the LCSP, there were two issues identified. In the beginning, a buffer prepared at LCSP did not pass quality control, and the CDC sent the reagent from Atlanta to help overcome the problem, causing delays in the analysis of specimens. Then, when the LCSP completed the analysis of all specimens, the inter-laboratory comparison of results for the measles antigen showed significant differences between LCSP and CDC. Since LCSP ran out of reagents to repeat standard curves to establish new cutoffs, the decision was to retest the specimens at the CDC. The analysis of specimens took longer due to the impact of the COVID-19 pandemic limiting laboratory access for CDC staff, but it was completed by the end of 2021. The results of the survey are expected to be available in 2023.
Progress. The first interprogrammatic group was established in 2018 with delegates from programs for neglected infectious diseases (NIDs), vaccine-preventable diseases (VPDs), malaria, the national laboratories directorate of the Ministry of Health, and the IBMP. The group proposed to carry out an integrated serosurvey using specimens from a sera bank of a national dengue study to obtain serology data for selected communicable diseases of interest in rural populations of the country's northern region. Due to the limited ability to respond to the research questions using the proposed sera bank, the group decided in 2021 to develop a new protocol. This revised protocol will use specimens collected regularly for the epidemiological surveillance of communicable diseases in hard-to-reach populations to carry out a retrospective integrated serosurvey. This effort involves additional partners such as the Institute of Scientific and Technological Communication and Information in Health at Fiocruz, the Evandro Chagas Institute, the Tropical Medicine Foundation, and the University of Sao Paulo, among others. The protocol is expected to be completed and implemented in 2023, as well as laboratory training on the Multiplex platform.
In addition to the three countries participating in the initiative, integrated serosurveillance has been expanded to countries that have implemented surveys to assess the epidemiological status of NIDs. Guatemala conducted a national survey to estimate the prevalence of soil-transmitted helminth infections in school-age children and 20 antigens related to ten diseases were tested on the Multiplex platform (Table 2). Guyana conducted a survey of school-age children in six regions of the country to determine the level of transmission of lymphatic filariasis, and tested serology for 18 antigens related to ten diseases. In these two countries, samples were analyzed at the CDC (Table 2).
Mexico was the only country in the initiative to complete the analysis of the integrated serosurvey results by the end of 2021. The laboratory group organized, cleaned, and validated the survey database. The laboratory team initially carried out a preliminary analysis of the raw laboratory results. Then, a database combining laboratory and survey results, including demographic data and risk factors of surveyed participants was compiled. This process took longer than expected since data entry from the paper-based questionnaires did not have adequate staff and time devoted to this task.
A statistician from CDC assisted in the analysis process for Mexico, including an in-person visit when the database was compiled. In 2019, the CDC and InDRE team worked together for several months to produce the first set of results. In February 2020, PAHO had an in-person visit to support the interpretation of results and to discuss them with the interprogrammatic team. Simple univariate and bivariate analysis of seroprevalence data, accounting for the cluster survey design, was produced for each group of diseases included in the survey. Serosurvey results were triangulated with program data to understand the results in the context of the surveyed populations. For instance, vaccine coverage by age cohorts and historic reports of cases and outbreaks of VPDs in the studied population were used to interpret seroprevalence for measles, rubella, and diphtheria.
Because of the survey design and nature of the survey as a pilot, the results were not robust enough to be used for programmatic decisions. However, the interprogrammatic team in Mexico understood the utility of serosurveillance as a complementary tool to characterize the transmission of communicable diseases and monitor the impact of interventions. The experience with the first integrated serosurvey in Mexico was used in 2021 to start developing a second serosurvey protocol.
In the meeting held in Mexico on March 2020 with delegates of countries and institutions participating in the Multiplex initiative, the need to reinforce country capacities to analyze and interpret integrated serosurveillance data was highlighted. In April 2021, PAHO and CDC conducted a five half-day virtual workshop with delegates from interprogrammatic groups of Brazil, Guatemala, Guyana, Mexico, and Paraguay focused on reinforcing skills to effectively use integrated serosurvey data. Theory and practical sessions were completed to review the rationale, concepts, approach, laboratory aspects, survey data preparation, data analysis, and data triangulation and interpretation.
PAHO and CDC published a toolkit to help countries to plan, implement, analyze, and use the results of integrated serosurveillance to improve programmatic decisions. This toolkit was developed based on the experience of the initiative.
Paraguay, Guatemala, and Guyana will complete and publish the analysis of results in 2023.
The following are the most important lessons learned from integrated serosurveillance in the Americas:
The country coordinating team should be clearly defined from the beginning and include those responsible for the programs, experts in the subject matter and diseases under study, statisticians, experts with experience in survey design, epidemiologists, laboratory technicians, and professionals with other profiles according to the proposed protocol and the expected use of results.
When monitoring several diseases at once, it is challenging to define the optimal age range and sample size to ensure the objectives of the study are met. Considering that, a household survey might be the best option, instead of a school-based survey. This would fulfill the needs of programs for diseases having significant transmission, or that require monitoring of routine immunization activities, in children below school age.
Proper training, supervision, and monitoring of field teams are crucial to ensure adherence to the methods and procedures established in the protocol. Logistical situations and contingencies that could affect fieldwork should be, when possible, identified in advance to adjust the timeline, resource, and financing requirements.
Disaggregated epidemiological data (e.g., cases and outbreaks) and historical data on interventions implemented (e.g., vaccination coverage, mass drug administration, etc.) are needed during the survey design phase to help define the research questions, and to interpret results using triangulation techniques.
While the MBA is more complex than single target assays for serology, the assay is robust, the technique is easy to train, and data are generated for multiple antigens in a single sample. Technology transfer is an ongoing process; close and continuous communication and support are critical among participating laboratories to maintain and revalidate laboratory capacities in countries.
In addition to improving laboratory capacities, it is crucial to ensure appropriate skills in survey design, statistical methods, data analysis, and interpretation to generate valid, reliable, and generalizable results to support actionable programmatic decisions. This process takes time and must integrate different disciplines, the programs' responsible, and the support of partners such as academies and research groups.
Table 3 presents some of the key aspects in the planning, implementation, data analysis, and decision-making to consider when implementing integrated serosurveys.