SARS-CoV-2 IgG Antibodies Seroprevalence and Sera Neutralizing Activity in MEXICO: A National Cross-Sectional Study during 2020.

José Esteban Muñoz-Medina,Angel Gustavo Salas-Lais,Teresita Rojas-Mendoza,Andrea Santos Coy-Arechavaleta,Clara Esperanza Santacruz-Tinoco,Ruth Lizzeth Madera-Sandoval,Célida Duque-Molina,Irma Eloísa Monroy-Muñoz,Cesar Raúl González-Bonilla,Joaquín González-Ibarra,Iliana Donají Palomec-Nava,Constantino López-Macías,Concepción Grajales-Muñiz,Vanessa Rivero-Arredondo,Larissa Fernandes-Matano,Julio Elías Alvarado-Yaah,Víctor Hugo Borja-Aburto

doi:10.3390/microorganisms9040850

Abstract

Until recently, the incidence of COVID-19 was primarily estimated using molecular diagnostic methods. However, the number of cases is vastly underreported using these methods. Seroprevalence studies estimate cumulative infection incidences and allow monitoring of transmission dynamics, and the presence of neutralizing antibodies in the population. In February 2020, the Mexican Social Security Institute began conducting anonymous unrelated sampling of residual sera from specimens across the country, excluding patients with fever within the previous two weeks and/or patients with an acute respiratory infection. Sampling was carried out weekly and began 17 days before Mexico’s first officially confirmed case. The 24,273 sera obtained were analyzed by chemiluminescent-linked immunosorbent assay (CLIA) IgG S1/S2 and, later, positive cases using this technique were also analyzed to determine the rate of neutralization using the enzyme-linked immunosorbent assay (ELISA). We identified 40 CLIA IgG positive cases before the first official report of SARS-CoV-2 infection in Mexico. The national seroprevalence was 3.5% in February and 33.5% in December. Neutralizing activity among IgG positives patients during overall study period was 86.1%. The extent of the SARS-CoV-2 infection in Mexico is 21 times higher than that reported by molecular techniques. Although the general population is still far from achieving herd immunity, epidemiological indicators should be re-estimated based on serological studies of this type.

Highlights

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can produce a wide spectrum of symptoms and disease severity, from mild and even asymptomatic cases to potentially fatal severe acute respiratory syndrome [1,2].According to the World Health Organization (WHO), through 31 December 2020, there were 83,955,204 SARS-CoV-2 infections and 1,820,400 deaths associated with COVID-19
To maintain a population-based focus, specimens were collected from 34 clinical laboratories (CLs; i.e., in each state’s main hospital) and 34 blood banks (BBs; i.e., in either the hospitals or unique to the respective states), across all 32 of the United Mexican States
The samples could come from any outpatient collection, excluding patients with fever within the previous two weeks and/or patients with an acute respiratory infection, because the majority of individuals infected with SARS-CoV-2 develop symptoms within a period of 14 days [11] and patients with an acute respiratory infection share symptoms similar to COVID-19 [12]

Summary

Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can produce a wide spectrum of symptoms and disease severity, from mild and even asymptomatic cases to potentially fatal severe acute respiratory syndrome [1,2].According to the World Health Organization (WHO), through 31 December 2020, there were 83,955,204 SARS-CoV-2 infections and 1,820,400 deaths associated with COVID-19. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can produce a wide spectrum of symptoms and disease severity, from mild and even asymptomatic cases to potentially fatal severe acute respiratory syndrome [1,2]. In Mexico, the first confirmed case occurred on 27 February 2020, and by 31 December 2020, 1,413,935 infections and 124,897 deaths were confirmed [4]. Since the publication of the first genome, diagnostic techniques based on molecular methods have been developed [5]. These show a high degree of sensitivity, especially quantitative reverse transcription PCR (RT-qPCR), which allows determination of the global incidence of SARS-CoV-2 and has been the basis of epidemiological surveillance during the first ten months of the pandemic. The number of officially reported cases is not claimed to reflect all cases; rather, it represents a set of cases that allow monitoring the behavior of the epidemic but not the totality of the disease burden [6]

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Conclusion