The Asian Development Bank (ADB) and the Ministry of Health of Viet Nam convened the 4th GMS Health Sector Working Group Meeting on 8 December 2021. The theme was “Solidarity through Information Exchange for COVID-19 Immunization in the GMS”. The COVID-19 Vaccines Global Access (COVAX) Facility, World Health Organization, United Nations Children's Fund, Save the Children, Sinovac and ADB presented experiences on COVID-19 vaccination and made recommendations for effective immunization in 2022. The meeting also shared next steps for scaling-up One Health actions in the GMS. Over 80 participants including senior health officials of GMS countries and representatives from development partners participated in the meeting.