Association Between COVID-19 Vaccination, Obesity, and Symptom Burden in a Mexican Population: A Retrospective Cross-Sectional Study

Background This study aimed to evaluate the association between the presence of COVID-19 symptomatology (quantified as total self-reported symptom count and validated by medical personnel) and obesity in vaccinated and unvaccinated individuals during the epidemiological period from July to December 2021. Methods A retrospective, cross-sectional epidemiological study was conducted using data from 2,008 adults with laboratory-confirmed SARS-CoV-2 infection identified during COVID-19 detection campaigns in multiple municipalities of Oaxaca, Mexico, between July and December 2021. Data on age, sex, body mass index (BMI) category, vaccination status, vaccine type, and reported symptoms were analyzed. SARS-CoV-2 infection was confirmed by rapid antigen testing followed by reverse transcription polymerase chain reaction (RT-PCR). The primary outcome was the total number of self-reported symptoms at diagnosis. Statistical analysis included descriptive statistics and one-way ANOVA with Tukey post hoc testing (p<0.05). Results Individuals with BMI above normal, particularly those who were unvaccinated and aged over 40 years (age was treated as a stratification variable), reported a higher number of COVID-19 symptoms. Vaccinated patients with elevated BMI showed a lower symptom burden compared with unvaccinated individuals. When analyzed by vaccine type, vaccination with Pfizer-BioNTech (BNT162b2) and CanSinoBio (Ad5-nCoV) was associated with a significantly lower number of reported symptoms, whereas no significant differences were observed for AstraZeneca (ChAdOx1 nCoV-19) or Sinovac (CoronaVac). No significant differences were found between sexes. Conclusions Obesity was associated with increased COVID-19 symptom burden in this population-based study. COVID-19 vaccination was associated with fewer reported symptoms among individuals with elevated BMI. Specifically, those vaccinated with Pfizer-BioNTech and CanSinoBio vaccines showed significant associations with reduced symptom burden, whereas vaccines from AstraZeneca and Sinovac did not. These findings support the relevance of vaccination strategies in populations with a high prevalence of obesity and highlight the need to consider metabolic factors and vaccine type when evaluating COVID-19 clinical presentation.