Humans 2 human 2 humanitarian crisis Altruism 1 COVID-19 1 COVID-19 Vaccines 1 COVID-19 vaccine booster 1 Conflict 1 Crisis 1 Disaster 1 Disaster Planning 1 Global Health 1 Global health 1 Health equity 1 Humanitarian 1 Note 1 Relief Work 1 SARS-CoV-2 1 SARS-CoV-2 vaccine 1 Safety 1 Vaccines 1 Volunteerism 1 Volunteers 1 adult 1 altruism 1 article 1 booster vaccination 1 coronavirus disease 2019 1 decision making 1 disaster 1