ChAdOx1 Vaccine Dose-Sparing Strategies: a Randomized Controlled Trial (COVID-19)

INTERVENTION: Dose‐sparing intradermal route,Dose‐sparing intramuscular route,Regular intramuscular route Experimental Biological/Vaccine,Experimental Biological/Vaccine,Active Comparator Biological/Vaccine one dose of 0.1 ml ChAdOx1/AZD1222 (AstraZeneca) intradermal route,one dose of 0.25 ml ChAdOx1/AZD1222 (AstraZeneca) intramuscular route,one dose of 0.5 ml ChAdOx1/AZD1222 (AstraZeneca) intramuscular route CONDITION: COVID‐19 Vaccine; SARS‐CoV‐2; Antibody; Cellular immunity; Post COVID‐19 exposure; intramuscular; intradermal Participants who recovered from COVID‐19 and participants who received only the first dose of Sinovac receiving ChAdOx1 vaccine ; COVID‐19 Vaccine; SARS‐CoV‐2; Antibody; Cellular immunity; Post COVID‐19 exposure; intramuscular; intradermal PRIMARY OUTCOME: SARS‐CoV‐2 antibodies Before vaccination, 4 weeks post vaccination IgG (ELISA), Neutralizing antibody (NeutraLISA) SECONDARY OUTCOME: Cellular immunity Before vaccination, 4 weeks post vaccination T cell (Fluorospot), Memory B cell (Fluorospot),COVID‐19 infection rate Before vaccination, 1 day post vaccination, 7 days post vaccination, 4 weeks post vaccination Symptom Assessment and confirmed with Real‐time RT‐PCR if suspected,Adverse events Before vaccination, 1 day post vaccination, 7 days post vaccination, 4 weeks post vaccination Patient report outcomes INCLUSION CRITERIA: 1. Age 18 years or more 2. Either Recovered from COVID‐19 OR Received only the first dose of Sinovac 3. Eligible for AstraZeneca Vaccination 4. Informed consent for participation