Details of SARS-CoV-2 seroprevalence surveys supported by the US CDC
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In a latest research posted to the medRxiv* preprint server, researchers reviewed and analyzed knowledge from extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serosurveys supported by the United States (US) Centers for Disease Prevention and Control (CDC) within the low- and middle-income (LMI) nations.

Study: U.S. CDC help to worldwide SARS-CoV-2 seroprevalence surveys, May 2020–February 2022. Image Credit: WildMedia/Shutterstock


Seroprevalence surveys assess the prevalence of pathogen-specific antibodies within the serum. Accordingly, they’ve been used to evaluate the prevalence of the human immunodeficiency virus (HIV), hepatitis B, and C viruses to tell the general public well being fashions for illness management and eradication.

SARS-CoV-2 seroprevalence survey knowledge might complement case-surveillance knowledge and likewise present essential data to information public well being methods. It might point out the precise burden of coronavirus illness 2019 (COVID-19), showcase the inhabitants immunity for a area, determine transmission hotspots and at-risk teams, and assist assess the vaccination protection.

Only 23% of seroprevalence research carried out throughout 2020 have been from LMI nations. Therefore, the CDC and different worldwide gamers, together with the World Health Organization (WHO), provided help for seroprevalence research within the LMI nations within the mid-2020.

About the research

The US CDC supported 72 worldwide serosurveys between May 12, 2020, and February 28, 2022, in 35 LMI nations. Via its workplaces within the LMI nations, the CDC supplied technical help (TA) on statistical, epidemiologic, laboratory strategies, and monetary help (FA) for these serosurveys. They additionally supplied coaching for sampling and laboratory methods, native employees, protocol improvement, knowledge evaluation, interpretation, and dissemination of the outcomes. Additionally, the CDC inspired nations to make use of the WHO UNITY protocol to make sure a point of standardization wherever attainable.

The US CDC activated its emergency operations heart in response to the COVID-19 pandemic on January 20, 2020, and created a global process power to deal with its incident administration system. Comprised primarily of the CDC employees, this workforce monitored the CDC’s function within the world response to implementation and monitoring of SARS-CoV-2 worldwide seroprevalence research and acquired funds from the Coronavirus Aid, Relief, and Economic Security (CARES) Act.

A digital month-to-month group name facilitated communication between the CDC headquarters and nation workplace employees engaged in seroprevalence work. A Microsoft Excel-based tracker for CDC-supported worldwide seroprevalence surveys helped the venture employees replace the standing of protocol improvement and implementation for every survey. The authors used this knowledge to assessment and analyze data for the present paper.

The present assessment describes all of the CDC-supported serosurveys with their objectives and traits. The evaluation covers the WHO area of the survey, research design and inhabitants surveyed, sort of help supplied by the CDC, viz., TA, FA, or each, laboratory testing used, survey implementation, and outcome dissemination standing. The researchers additionally talk about the challenges confronted in the course of the survey implementation and steered measures to make use of serosurvey knowledge to tell public well being motion.

Study findings

Of the 72 serosurveys supported by the CDC, 61% acquired each TA and FA, whereas 30% and three% acquired solely TA and solely FA, respectively. The remaining six % have been a part of the casual evaluations.

Regarding the audience, 54% of those surveys focused the overall inhabitants throughout the WHO African area, whereas 13%, 7%, and seven% focused pattern pregnant girls, healthcare employee cohorts, and different particular inhabitants segments, reminiscent of sufferers, and college students, and many others., respectively. The remaining 18% focused different populations, e.g., truck drivers. 

Interestingly, round 55% of research used an enzyme-linked immunosorbent assay (ELISA) to detect SARS-CoV-2 antibodies in serum, whereas solely 11% used a speedy antigen check. While the researchers assessed 63% of survey rounds towards WHO UNITY standards, solely 79% used strategies aligned with its standards. The CDC-supported research have been in numerous phases of implementation. Notably, they have been carried out by the native governments, which had possession over the info. However, CDC might acquire restricted and momentary entry to seroprevalence knowledge for evaluation.

A meager 34 serosurvey rounds had accomplished knowledge assortment, whereas solely 5 research (6%) carried out in Africa have been revealed. Among the revealed knowledge, SARS-CoV-2 seroprevalence estimates ranged from 2.1% in Zambia to 34.7% in Kenya. Likewise, an infection to reported circumstances ratios ranged from 21:1 in Ethiopia to 295:1 in Senegal.


The help supplied by the CDC strengthened the native capability to conduct SARS-CoV-2 epidemiologic surveillance in a number of LMI nations. However, the challenges within the research implementation and the interpretation of seroprevalence outcomes always developed.

Therefore, it was essential to determine and forecast epidemic patterns over time, resolve the long-lingering query of correlates of safety (CoP) for SARS-CoV-2, and combine COVID-19 serosurveillance with surveillance of different pathogens, together with Plasmodium species, Dengue viruses, and different human coronaviruses. Notably, antigenic cross-reactivity between SARS-CoV-2 and these pathogens fetch false-positive outcomes for SARS-CoV-2 serologic testing. To tackle this, CDC really useful conducting impartial in-country validations of outcomes, particularly within the WHO African area.

The introduction of COVID-19 vaccines additionally challenged the design and implementation of SARS-CoV-2 serosurveys and the interpretation of their outcomes. For occasion, within the nations the place a SARS-CoV-2 serosurvey design couldn’t distinguish between pure and vaccine-induced immunity, it couldn’t determine doubtlessly at-risk populations and allocate vaccines effectively. Likewise, the phenomenon of the waning of immunity hampered the evaluation of each the precise burden of COVID-19 and vaccination protection.

It is noteworthy that the kind of antibody assay, check timing, and severity of an infection influence the efficacy of serosurveys. Therefore, the CDC launched new seroprevalence protocols. They additionally tailored the existent ones to handle the epidemiologic, laboratory, and different concerns of vaccine introduction. Overall, the CDC’s help for worldwide seroprevalence surveys drastically helped information public well being interventions to manage the unfold of the COVID-19 pandemic on the world degree.

*Important discover

medRxiv publishes preliminary scientific experiences that aren’t peer-reviewed and, subsequently, shouldn’t be considered conclusive, information scientific follow/health-related habits, or handled as established data.

Journal reference:

  • Hamida, A. et al. (2022) “U.S. CDC support to international SARS-CoV-2 seroprevalence surveys, May 2020–February 2022″. medRxiv. doi: 10.1101/2022.06.01.22275786. material/10.1101/2022.06.01.22275786v1

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