The safety and tolerability of 1 dose of AZD2816 in the previously vaccinated cohort with AZD1222;The safety and tolerability of 1 dose of AZD2816 in the previously vaccinated cohort with AZD1222;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in the unvaccinated cohort;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in the unvaccinated cohort;To determine if the response against B.1.351 elicited by an AZD2816 booster dose in participants previously vaccinated with AZD1222 is non-inferior to the response against Wuhan-Hu-1 strain elicited by 2-dose AZD1222 administered to naïve participants;To determine if the response against the B.1.351 variant elicited by a 2-dose AZD2816 vaccination is non-inferior to the response against the original Wuhan-Hu-1 strain elicited by a 2-dose AZD1222 vaccination in the unvaccinated cohort

The safety and tolerability of 1 dose of AZD2816 in the previously vaccinated cohort with AZD1222;The safety and tolerability of 1 dose of AZD2816 in the previously vaccinated cohort with AZD1222;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in the unvaccinated cohort;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in the unvaccinated cohort;To determine if the response against B.1.351 elicited by an AZD2816 booster dose in participants previously vaccinated with AZD1222 is non-inferior to the response against Wuhan-Hu-1 strain elicited by 2-dose AZD1222 administered to naïve participants;To determine if the response against the B.1.351 variant elicited by a 2-dose AZD2816 vaccination is non-inferior to the response against the original Wuhan-Hu-1 strain elicited by a 2-dose AZD1222 vaccination in the unvaccinated cohort

The safety and tolerability of 1 dose of AZD2816 in the previously vaccinated cohort with AZD1222;The safety and tolerability of 1 dose of AZD2816 in the previously vaccinated cohort with AZD1222;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in the naïve unvaccinated cohort;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in the naïve unvaccinated cohort;To determine if the response against B.1.351 elicited by an AZD2816 booster dose in participants previously vaccinated with AZD1222 is non-inferior to the response against Wuhan-hu-1 strain elicited by 2-dose AZD1222 administered to naïve participants;To determine if the response against the B.1.351 variant elicited by a 2-dose AZD2816 vaccination is non-inferior to the response against the original Wuhan-hu-1 strain elicited by a 2-dose AZD1222 vaccination in the naïve unvaccinated cohort

The safety and tolerability of 1 dose of AZD2816 in the previously vaccinated cohort with AZD1222;The safety and tolerability of 1 dose of AZD2816 in the previously vaccinated cohort with AZD1222;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in the naïve unvaccinated cohort;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in the naïve unvaccinated cohort;To determine if the response against B.1.351 elicited by an AZD2816 booster dose in participants previously vaccinated with AZD1222 is non-inferior to the response against Wuhan-hu-1 strain elicited by 2-dose AZD1222 administered to naïve participants;To determine if the response against the B.1.351 variant elicited by a 2-dose AZD2816 vaccination is non-inferior to the response against the original Wuhan-hu-1 strain elicited by a 2-dose AZD1222 vaccination in the naïve unvaccinated cohort

Describe the humoral immune responses against the B.1.351 and Wuhan-Hu-1 strains induced by 1 dose of AZD2816 in seronegative participants previously vaccinated with AZD1222/SARS-CoV-2 mRNA vaccine;Describe the humoral immune responses against the B.1.351 and Wuhan-Hu-1 strains induced by a 2-dose primary vaccination with AZD2816 in unvaccinated seronegative participants;The safety and tolerability of 1 dose of AZD2816 in seronegative participants previously vaccinated with AZD1222;The safety and tolerability of 1 dose of AZD2816 in seronegative participants previously vaccinated with AZD1222;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in unvaccinated seronegative participants;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in unvaccinated seronegative participants;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in unvaccinated seronegative participants

Describe the humoral immune responses against the B.1.351 and Wuhan-Hu-1 strains induced by 1 dose of AZD2816 in seronegative participants previously vaccinated with AZD1222/SARS-CoV-2 mRNA vaccine;Describe the humoral immune responses against the B.1.351 and Wuhan-Hu-1 strains induced by a 2-dose primary vaccination with AZD2816 in unvaccinated seronegative participants;The safety and tolerability of 1 dose of AZD2816 in seronegative participants previously vaccinated with AZD1222;The safety and tolerability of 1 dose of AZD2816 in seronegative participants previously vaccinated with AZD1222;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in unvaccinated seronegative participants;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in unvaccinated seronegative participants;The safety and tolerability of a 2-dose primary vaccination with AZD2816 in unvaccinated seronegative participants