and J.A.-M.; technique, L.F.-M., .G.S.-L. propose effective vaccination schedules for vulnerable populations. Keywords:abdominal obesity, COVID-19, vaccines, humoral immune response == 1. Introduction == Coronavirus disease (COVID-19) is caused by the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), which has spread worldwide since the first cases were reported in 2019, becoming a pandemic in 2020 [1]. Various comorbidities have been implicated as risk factors for deterioration or poor outcomes in patients with COVID-19. Among the comorbidities, obesity is one of the most significant [2], although the underlying factors have not been fully elucidated. Obesity has a high prevalence worldwide. In 2016, the Worldwide Health Organization (WHO) reported that 39% of adults were overweight and 13% were obese [3]. In Mexico, the situation was even more alarming; according to data from the National Health and Nutrition Survey (ENSANUT) 201819, the prevalence of overweight was 39.1%, obesity was 36.1%, and abdominal adiposity was 81.6% [4]. Having a high prevalence of individuals with obesity and overweight in Mexico makes the population more susceptible to complications from COVID-19. There are reports of a negative influence of obesity on the immune response against SARS-CoV-2, as people with a higher body mass index (BMI) have a higher risk of hospitalization, more severe symptoms of the disease, a higher risk of mechanical ventilation [5,6,7], and lower antibody levels induced by COVID-19 and vaccination [8,9]. However, BMI can be used only as an approximation of the degree of adiposity [3] because it does not consider body fat distribution, especially visceral fat. Visceral fat is a risk factor for several cardiometabolic NBMPR diseases and is associated with a high mortality [10]. Waist/hip ratio is associated with a higher risk of death, cardiovascular disease, and diabetes than BMI. Waist circumference (WC) is strongly associated with the absolute Igf1 amount of abdominal and visceral fat [11]. Abdominal adipose tissue has been reported to express several proinflammatory mediators that can generate a systemic inflammatory state and compromise lung function [12,13]. Likewise, central obesity is associated with an increased risk of developing severe COVID-19, a high risk of hospital admission, and with long hospital stays [14,15,16]. Excess visceral fat 128.5 cm2is independently associated with the severity of COVID-19 [17]. Graziano et al. showed that visceral adiposity is a more sensitive parameter than BMI for predicting negative COVID-19 outcomes [18], as well as in other studies in which people with abdominal obesity (AO) had low levels of vaccination-induced antibodies in the Chinese population [19] and health workers from Italy [20,21]. In Mexico, different vaccines against COVID-19 were administered to the general population, allowing the evaluation of the effect of AO on the production of antibodies induced by the infection or by the application of the vaccines and their reactogenicity (physical manifestations of the inflammatory response to vaccination: fever, tiredness, headache, muscle pain, shaking chills, diarrhea, and local reaction). NBMPR Therefore, our main objective was to evaluate the impact of AO on the IgG antibody response induced by SARS-CoV-2 infection or from the application of any of the five vaccination schemes in Mexican individuals. Second, we analyzed the role of AO in symptomatology and reactogenicity generated NBMPR by the application of vaccines. Finally, we evaluated the effect of other factors, such as documenting prior COVID-19, BMI, age, sex, comorbidities, and type of vaccine administered, on antibody levels. == 2. Materials and Methods == == 2.1. Ethics Statements == This study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Ethics and Scientific Committee of the National Scientific Research Commission of the IMSS (Mexican Institute of Social Security). This study is part of the project Seroprevalence and neutralizing activity of SARS-CoV-2 IgG antibody seroprevalence sera in Mexico approved on 13 March 2020 with registration number R-785-2020-60. The study participants were selected based on voluntary application, and informed consent was obtained from all subjects. For the monitoring of the participants and analysis of the samples, an amendment to the project was requested, which was approved on 10 August 2022 with registration.