Background: Although vaccination effectively prevents severe outcomes due to COVID-19, its role in preventing household transmission remains unclear. This study aimed to investigate the association between vaccination and household transmission of COVID-19 in Bali, Indonesia. Subjects and Method: A cross-sectional study was conducted in Bali, Indonesia, in September 2021 as part of the vaccine evaluation program. Total of 1,000 individuals with COVID-19 who resided in high (Denpasar city) and low transmission areas (Karangasem, Gianyar, and Klungkung) for COVID-19 were randomly chosen from the COVID-19 notifications for the period of January to June 2021. The interview was carried out to collect demographic characteristics, vaccination status, index cases, number of household contacts, and number of secondary cases. The secondary attack rate in the household was calculated. Logistic regression was performed to examine the association between COVID-19 transmission rate and vaccination status. Results: Total of 121 (12.1%) index cases were identified among 1000 selected individuals. The secondary attack rate was slightly higher in high transmission areas (1.82) compared to low transmission areas (1.33). While it is not statistically significant, compared to unvaccinated individuals, the probability of being index cases among those who had been vaccinated were lower both in high transmission area (OR= 0.86; 95% CI=0.52 to 1.43; p= 0.562) and low transmission area (OR= 0.79; 95% CI= 0.40 to 1.57; p= 0.497), respectively. Furthermore, index cases with COVID-19 vaccination in high incidence areas are more likely to be low transmitting COVID19 state (OR=0.65; 95% CI=0.25 to 1.69; p=0.373). While in the Low Incidence Area, index cases with COVID-19 vaccination are more likely to be high transmitting COVID19 state (OR= 3.06; 95% CI=0.75 to 12.56; p= 0.125). Conclusion: Vaccination may reduce the risk of SARS-CoV-2 transmission within the household. Keywords: vaccination, COVID-19, the index case, household transmission Correspondence: Anton Suryatma. Center for Research and Development of Public Health, National Institute of Health Research and Development, Jakarta. Jl. Percetakan Negara 29 Jakarta. Email: drantonsuryatma@gmail.com. Mobile: +62 8561489348.