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

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.

Seroepidemiology of SARS-CoV-2 in healthcare personnel working at the largest tertiary COVID-19 referral hospitals in Mexico City

“…This study was conducted later during the pandemic than other studies with similar and lower prevalence [ 8 – 10 , 33 ]; thus, the observed high prevalence may be explained by higher accumulation of cases. Second, our results are consistent with those of two large, national, seroepidemiological surveys, that observed that approximately one third of the general population had been exposed to SARS-CoV-2 by December 2020 [ 3 , 6 , 7 ]. This could be especially true in large urban centers such as Mexico City, which has contributed with a large proportion of the total national cases [ 1 , 3 ].…”

“…We enrolled participants during the second wave, which in Mexico City reached an estimated cumulative incidence of 434 cases per 100,000-person, reaching a maximum of 7371 cases per day (and over 20,000 cases per day at the country level) [ 1 , 5 ]. Preliminary and recently published results of nationally representative seroepidemiological surveys in Mexico estimated that over one third of the general population had been exposed to SARS-CoV-2 in Mexico by December 2020 [ 6 , 7 ]. While prevalence depends on the moment of estimation, as well as on duration of immunity, it is expected to increase after each epidemiological wave.…”

The impact of the COVID-19 pandemic among migrants in shelters in Tijuana, Baja California, Mexico

“…According to that study, the seroprevalence for the northwest region (including Baja California) was 40.7%. 25 A study conducted among people who inject drugs in Tijuana during the same period as this study found that 36.5% tested SARS-CoV-2 positive. 3 Our seroprevalence results are, therefore, consistent with the review by Hayward et al who concluded that migrants have been disproportionately affected during the pandemic, when compared with the native-born or general population and should be targeted in prevention efforts.…”

Seroprevalence of SARS-CoV-2 antibodies in blood donors during the third wave of infection in Campeche Mexico

“…By the end of 2020, previous studies in Campeche, Mexico and before the vaccination program started, showed the seroprevalences were between 10%–20% in the unvaccinated population [ 11 ]. In the present work 42 % (60/141) corresponded to unvaccinated subjects.…”

“…Unfortunately, in Mexico there have been few publications in base-population to capture enough epidemiological data; two works at national level describe the transmission dynamics during 2020, indicating a national prevalence of 24–33 % by the end 2020 [ 10 , 11 ]. Two more other studies were carried out in cities located in the northern and southeastern part of Mexico during the same year of 2020; the seroprevalence was 27 % and 21 %, respectively by the end of the same year [ 12 , 13 ].…”