Obesity is associated with an increased risk of contracting infections. This study aimed to estimate the risk of COVID-19 infection associated with obesity and to assess its role in the specific antibody response against SARS-CoV-2 in 2021. This study included 980 participants from the State of Mexico who participated in a serological survey where they were tested for SARS-CoV-2 IgG anti-S1/S2 and anti-RBD antibodies and asked for height, weight, and previous infection data via a questionnaire. Of the cohort of 980 participants, 451 (46.02%) were seropositive at the time of recruitment (45.2% symptomatic and 54.8% asymptomatic). The risk of SARS-CoV-2 infection with obesity was 2.18 (95% CI: 1.51–3.16), 2.58 (95% CI: 1.63–4.09), and 1.88 (95% CI: 1.18–2.98) for seropositive, asymptomatic, and symptomatic individuals, respectively, compared to those with normal weight. Anti-S1/S2 and anti-RBD IgG antibodies tended to be higher in overweight and obese participants in the seropositive group and stratified by different obesity classes. Additionally, there was a positive correlation between anti-S1/S2 and anti-RBD IgG antibodies and BMI in both men and women in the seropositive group. Obesity is an independent risk factor for SARS-CoV-2 infection when adjusted for confounding variables; however, the relationship between BMI and anti-S1/S2 and anti-RBD IgG antibody levels differed markedly in the presence or absence of symptoms.

Abdominal obesity is highly prevalent in Mexico and has a poor prognosis in terms of the severity of coronavirus disease (COVID-19) and low levels of antibodies induced by infection and vaccination. We evaluated the humoral immune response induced by COVID-19 and five different vaccination schedules in Mexican individuals with abdominal obesity and the effects of other variables. This prospective longitudinal cohort study included 2084 samples from 389 participants. The levels of anti-S1/S2 and anti-RBD IgG antibodies were measured at various time points after vaccination. A high prevalence of hospitalization and oxygen use was observed in individuals with abdominal obesity (AO) who had COVID-19 before vaccination; however, they also had high levels of anti-S1/S2 and anti-RBD-neutralizing IgG antibodies. The same was true for vaccination-induced antibody levels. However, their longevity was low. Interestingly, we did not observe significant differences in vaccine reactogenicity between abdominally obese and abdominally non-obese groups. Finally, individuals with a higher body mass index, older age, and previous COVID-19 had higher levels of antibodies induced by COVID-19 and vaccination. Therefore, it is important to evaluate other immunological and inflammatory factors to better understand the pathogenesis of COVID-19 in the presence of risk factors and to propose effective vaccination schedules for vulnerable populations.

The persistence of qPCR positivity for SARS-CoV-2 in individuals who recovered from COVID-19 raised several questions regarding viral transmission, with a special interest in healthcare professionals who may pose a risk of transmitting SARS-CoV-2. This issue highlights the necessity for identifying the genetic risk factors associated with persistent SARS-CoV-2 infection. A promising target for achieving this goal is the angiotensin-converting enzyme 2 (ACE2) gene, which has been associated with clinical characteristics of COVID-19 infection, such as severity. The analysis of samples from the first wave of the COVID-19 pandemic represents the initial response of the immune human system against this new virus, without the effect of vaccination or the presence of multiple strains. The aim of this study was to analyze the association of genetic variants in ACE2 with persistent SARS-CoV-2 infection. We conducted a case–control study, including 151 healthcare workers who tested positive for SARS-CoV-2 by qPCR during the first wave of the COVID-19 pandemic, and who were followed up until their results were negative. ACE2 was sequenced through Sanger sequencing. The sequence was compared against a reference sequence and variants identified. Four ACE2 variants were associated with persistent SARS-CoV-2 qPCR positivity. Three of the variants with an effect on the resulting protein were associated with increased risk of persistent SARS-CoV-2 qPCR positivity, NG_012575.2:g.35481 C>T, NG_012575.2:g.35483 G>T and NG_012575.2:g.35498 G>T. On the other hand, the rs2285666 (NG_012575.2:g.14934 G>A) was associated with a higher risk for persistent SARS-CoV-2 qPCR positivity in women and rs4646150 (NG_012575.2:g.25701 G>A) in men. The NG_012575.2:g.35498 G>T variant represents an amino acid change with a possibly harmful effect on ACE2 function. Our results suggest that ACE2 variants might be useful for identifying the population at higher risk for developing persistent SARS-CoV-2-positive qPCR results. This knowledge can be helpful for designing health policies for protecting healthcare professionals and, in consequence, users of health services.