Bangladesh has fully vaccinated 76 per 100 population against COVID-19. However, ensuring higher coverage in vulnerable sites is subject to various challenges. We report the COVID-19 vaccine uptake and its correlates among the adults residing in two vulnerable sites in Bangladesh. We conducted a cross-sectional study between August and September 2022 in two sites with a high prevalence of in- and out-migration. Duaripara, a slum in northeast Dhaka, was selected as the in-migration site. Tala, a disaster-prone sub-district located in southwest Satkhira, was selected as the out-migration site. We surveyed 2502 adults (1239 from Duaripara; 1263 from Tala) from 1211 randomly selected households. We reported coverage and examined associations between the uptake and background characteristics using Poisson, and Two-part regression models. Additionally, we checked for spatial autocorrelation to assess equitable distribution geographically. The coverage for the first and second doses of the COVID-19 vaccine were about 91% and 80.3% in Duaripara, and 96.6% and 92.2% in Tala, respectively. For the third dose, it was about 14% in Duaripara and 52.4% in Tala. For Tala, the uptake was significantly associated with age, education, and occupation. Interestingly, it was associated positively with television access (Incidence rate ratio: 1.04, p-value = 0.01) and negatively with smart-phone access (IRR: 0.96, p-value = 0.04). Respondents who temporarily migrated were more likely to remain unvaccinated (IRR: 0.90, p-value