adult 2 controlled study 2 female 2 human major clinical study 2 male 2 physician Adolescent 1 Adult 1 Article 1 COVID-19 Vaccines 1 Covid-19 1 Cross-Sectional Studies 1 Female 1 Health Care Costs 1 Health Expenditures 1 Humans 1 Immunization 1 Male 1 Middle Aged 1 Patients 1 RCT 1 SARS-CoV-2 vaccine 1 Viet Nam 1 Vietnam 1 Willingness To Pay 1 adolescent 1 agricultural worker 1 article 1 civil servant 1