Phase II; To assess the composite endpoints of safety and reactogenicity of a the single and two-dose schedule of RBD SARS-CoV-2 HBsAg VLP vaccine administration as compared with placebo in healthy adults aged 18 - 79 years as determined through participant reported and clinically identified local and systemic adverse events. This will include safety blood assessment and the recording of solicited and unsolicited local and systemic adverse events by participants via an electronic diary or by the clinical staff as part of scheduled clinic visits[Participant reported events reported daily for 7 days post-vaccination and then on occurrence up to 180 days post-vaccination];Phase II; To assess the immune response of a two-dose schedule of two dose amounts of RBD SARS-CoV-2 HBsAg VLP vaccine as compared with two-dose administration of placebo in healthy adults aged 18 - 79 years as determined through changes in participant immunity 56 days from first dose. To assess the immune response following a single-dose schedule of RBD SARS-CoV-2 HBsAg VLP vaccine as compared with placebo in healthy adults aged 18 - 79 years as determined through changes in participant immune response 56 days after receiving the vaccine dose. Immune response will be measured through analysis of blood samples.[Increase in neutralising antibody titres as measured through to day 56];Phase I: To assess the composite endpoints of vaccine safety and reactogenicity of a two-dose schedule of two dose amounts of RBD SARS-CoV-2 HBsAg VLP vaccine as compared with two-dose administration of placebo in healthy adults aged 18 - 45 years as determined through participant reported (solicited and unsolicited) and clinically identified local and systemic adverse events (e.g. blood tests; vital signs; physical examination).[Participant reported events reported daily for 7 days post-vaccination and then on occurrence up to 180 days post-vaccination]

Phase II; To assess the composite endpoints of safety and reactogenicity of a the single and two-dose schedule of RBD SARS-CoV-2 HBsAg VLP vaccine administration as compared with placebo in healthy adults aged 18 - 79 years as determined through participant reported and clinically identified local and systemic adverse events. This will include safety blood assessment and the recording of solicited and unsolicited local and systemic adverse events by participants via an electronic diary or by the clinical staff as part of scheduled clinic visits[Participant reported events reported daily for 7 days post-vaccination and then on occurrence up to 180 days post-vaccination];Phase II; To assess the immune response of a two-dose schedule of two dose amounts of RBD SARS-CoV-2 HBsAg VLP vaccine as compared with two-dose administration of placebo in healthy adults aged 18 - 79 years as determined through changes in participant immunity 56 days from first dose. To assess the immune response following a single-dose schedule of RBD SARS-CoV-2 HBsAg VLP vaccine as compared with placebo in healthy adults aged 18 - 79 years as determined through changes in participant immune response 56 days after receiving the vaccine dose. Immune response will be measured through analysis of blood samples.[Increase in neutralising antibody titres as measured through to day 56];Phase I: To assess the composite endpoints of vaccine safety and reactogenicity of a two-dose schedule of two dose amounts of RBD SARS-CoV-2 HBsAg VLP vaccine as compared with two-dose administration of placebo in healthy adults aged 18 - 45 years as determined through participant reported (solicited and unsolicited) and clinically identified local and systemic adverse events (e.g. blood tests; vital signs; physical examination).[Participant reported events reported daily for 7 days post-vaccination and then on occurrence up to 180 days post-vaccination]