1. Healthy children between 5-11 years of age 2. No history of COVID-19 infection 3. Parents or guardians live in Bangkok and give informed consent to participate 4. Children between 7-11 years of age give informed assent to participate

1. Healthy children between 5-11 years of age 2. No history of COVID-19 infection 3. Parents or guardians live in Bangkok and give informed consent to participate 4. Children between 7-11 years of age give informed assent to participate