Efficacy and Safety of Heterologous and Homologous COVID-19 Vaccination

The investigators would like to conduct a prospective analysis to compare the same adenovirus vector ChAdOx1-nCov-19 (Astra-Zeneca) or SARS-CoV-2 messenger RNA-1273 (Moderna) vaccine inoculation and mixed inoculation of ChAdOx1-nCov-19 and messenger RNA-1273 vaccine. Healthy volunteers (including medical personnel) will be enrolled and divided into five groups according to their wishes. The five groups are: the first group is the subjects who received ChAdOx1- nCov-19 vaccine with 8 weeks apart; the second group is the SARS-CoV-2 messenger RNA-1273 vaccine after the first dose of ChAdOx1-nCov-19 vaccination with 8 weeks apart; the third group is the first dose of ChAdOx1-nCov-19 vaccine and the SARS-CoV-2 messenger RNA-1273 vaccine with 4 weeks apart; the fourth group is the SARS-CoV-2 messenger RNA-1273 vaccination with 4 weeks apart; the fifth group is the first dose of ChAdOx1-nCov-19 vaccine and the SARS-CoV-2 messenger RNA-1273 vaccine with 12 weeks apart. There will be 100 volunteers in each group, and blood will be drawn for antibody test on the day before and the 14th, 28th day and 12th week after the second dose of vaccination, including 100 subjects in each group for SARS-CoV-2 ELISA antibody titer and 50 people in each group for SARS-CoV-2 neutralizing antibody titer. This study analyzo the titers of SARS-CoV-2 antibodies, and records adverse reactions at each visits including the first day, the 14th day, the 28th day, and the 12th week (including those within 7 days after the inoculation). Adverse reactions and whether there is development of COVID-19 within 6 months will be recorded. The research team will also follow up by phone in the 6th month to ask whether there is vaccine associated adverse events or SARS-CoV-2 infection. The results will provide information for vaccine policy in Taiwan.