In a recent study published on the medRxiv * prepress server, researchers reviewed and analyzed data from serological surveys of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) supported by the Centers for Disease Prevention and Control (CDC). ) of the United States (USA). low and middle income countries (LMI).
Study: US CDC support for SARS-CoV-2 international seroprevalence surveys, May 2020-February 2022. Image credit: WildMedia / Shutterstock
Fund
Seroprevalence surveys assess the prevalence of specific antibodies to pathogens in serum. Accordingly, they have been used to assess the prevalence of human immunodeficiency virus (HIV), hepatitis B and C viruses to inform public health models for disease control and eradication.
SARS-CoV-2 seroprevalence survey data could complement case surveillance data and also provide critical information to guide public health strategies. It could indicate the actual burden of coronavirus disease 2019 (COVID-19), show the immunity of the population of a region, identify transmission points and risk groups, and help assess vaccination coverage.
Only 23% of seroprevalence studies conducted during 2020 were from LMI countries. Therefore, the CDC and other international actors, including the World Health Organization (WHO), provided support for seroprevalence studies in LMI countries in mid-2020.
About the study
The US CDC supported 72 international serological surveys between May 12, 2020 and February 28, 2022 in 35 LMI countries. Through its offices in LMI countries, the CDC provided technical assistance (TA) on statistical, epidemiological, laboratory, and financial assistance (FA) methods for these serological surveys. They also provided training in sampling and laboratory techniques, local staff, protocol development, data analysis, interpretation and dissemination of results. In addition, the CDC encouraged countries to use the WHO UNIT protocol to ensure a certain degree of standardization whenever possible.
The U.S. CDC activated its emergency operations center in response to the COVID-19 pandemic on January 20, 2020, and set up an international working group to manage its incident management system. Formed primarily by CDC staff, this workforce oversaw the role of the CDC in the global response to the implementation and monitoring of international SARS-CoV-2 seroprevalence studies and received funding from the Aid, Relief and Prevention Act. economic security of coronavirus (CARES).
A virtual monthly group call facilitated communication between the CDC headquarters and the country’s office staff engaged in seroprevalence work. A Microsoft Excel-based crawler for international seroprevalence surveys with CDC support helped project staff update the status of protocol development and implementation for each survey. The authors used this data to review and analyze the information in the current document.
The current review describes all serological surveys supported by the CDC with their objectives and characteristics. The analysis covers the WHO region of the survey, the design of the study and the population surveyed, the type of assistance provided by the CDC, ie TA, FA or both, laboratory tests used, the implementation of the survey and the state of dissemination of the results. The researchers also discussed the challenges they face during the implementation of the survey and suggested measures to use the data from the serological survey to inform public health action.
Study results
Of the 72 serological surveys supported by the CDC, 61% received both TA and FA, while 30% and 3% received only TA and only FA, ​​respectively. The remaining six percent were part of the informal reviews.
As for the target audience, 54% of these surveys were aimed at the general population of the WHO African region, while 13%, 7% and 7% were aimed at samples of pregnant women, cohorts of health workers and other specific segments of the population, such as patients, and students, etc., respectively. The remaining 18% went to other towns, for example, truck drivers.
Interestingly, about 55% of the studies used an enzyme-linked immunosorbent assay (ELISA) to detect serum SARS-CoV-2 antibodies, while only 11% used a rapid antigen test. While the researchers evaluated 63% of the survey rounds according to WHO UNITY criteria, only 79% used methods aligned with their criteria. CDC-supported studies were at different stages of implementation. In particular, they were conducted by local governments, who owned the data. However, the CDC could gain limited and temporary access to seroprevalence data for analysis.
A scant 34 rounds of sero-survey had completed data collection, while only five studies (6%) conducted in Africa were published. Among the published data, seroprevalence estimates of SARS-CoV-2 ranged from 2.1% in Zambia to 34.7% in Kenya. Similarly, infection rates and reported cases ranged from 21: 1 in Ethiopia to 295: 1 in Senegal.
Conclusions
CDC assistance strengthened local capacity to conduct SARS-CoV-2 epidemiological surveillance in several LMI countries. However, the challenges in implementing the study and interpreting the results of seroprevalence were constantly evolving.
Therefore, it was crucial to identify and predict epidemic patterns over time, resolve the long-standing issue of protection correlates (CoP) for SARS-CoV-2, and integrate COVID-19 serovigilance with surveillance of other pathogens, including the species Plasmodium, Dengue Virus and other human coronaviruses. In particular, antigenic cross-reactivity between SARS-CoV-2 and these pathogens yields false-positive results for SARS-CoV-2 serological testing. To address this, the CDC recommended that independent validations of results be performed in the country, especially in the WHO African region.
The introduction of COVID-19 vaccines also challenged the design and implementation of SARS-CoV-2 serum surveys and the interpretation of their results. For example, in countries where a SARS-CoV-2 serum survey design could not distinguish between natural and vaccine-induced immunity, it could not identify potentially at-risk populations and allocate vaccines efficiently. Likewise, the phenomenon of decreased immunity made it difficult to assess both the actual COVID-19 load and vaccine coverage.
It should be noted that the type of antibody assay, the timing of the test, and the severity of the infection affect the effectiveness of serological tests. Therefore, the CDC introduced new seroprevalence protocols. They also adapted existing ones to address epidemiological, laboratory, and other considerations of vaccine introduction. Overall, CDC support for international seroprevalence surveys has been instrumental in guiding public health interventions to control the spread of the COVID-19 pandemic worldwide.
* Important news
medRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered conclusive, guided by clinical practice or health-related behavior, or treated as established information.