For Biomedical Vancouver you need to record all authors in your final reference list or bibliography. You can only use et al. if there are 10 or more authors. For example:

Less than 10 authors

(11) Jarvis H, Craig D, Barker R, Spiers G, Stow D, Anstee QM, Hanratty B. Metabolic risk factors and incident  advanced liver disease in non-alcoholic fatty liver disease (NAFLD): A systematic review and meta-analysis of population-based observational studies. PLoS Medicine. 2020;17(4).

10 or more authors

(12) Yap TA, Siu LL, Calvo E, Lolkema MP, LoRusso PM, Soria J-C, et al. SARS-CoV-2 vaccination and phase 1 cancer clinical trials. The Lancet Oncology. 2021; 22(3):298-301.