Background Women sex workers are considered vulnerable to sexually transmitted infections, such as hepatitis B and the human immunodeficiency virus (HIV), considering the unfavourable conditions by making verbal agreement with their clients. The study aimed to evaluate the adherence of female sex workers to three doses of hepatitis B vaccine.

Methods Cross-sectional study with female sex workers in the city of Teresina, Brazil. The study included 402 women, using the “snowball” technique. Sociodemographic data were gotten by individual interview, blood sampling for anti-HBs evaluation was collected and the doses of vaccine against hepatitis B were administered, according to the need and acceptance of participants. Data were analysed using Statistical Package for Social Science (SPSS) 18.0.

Results Of the 402 women who participated in study, 96 (23.8%) reported ever having received at least one dose of the vaccine, while 25 (6.2%) reported having received one dose only, 14 (3.4%) received two doses, 57 (14.1%) reported having received three doses and 50 (12.4%) did not know. Of those who reported having received three doses was carried anti-HBs, and reagent in 33 (50.7%). Thus, 57 (14.1%) reported already received three doses and 30 (7.4%) refused to receive the vaccine. Thus, 315 women were vaccinated. Of this total, 223 (70.7%) women receiving two doses and only 92 (22.8%) completed the scheme with three doses of the vaccine.

Conclusion Complete squeme of three doses of the vaccine in this population is challenging, it is necessary for both immunisation strategies and improving access of this population to public health, mainly through primary care.