Evaluation of Full Versus Fractional Doses of COVID-19 Vaccines Given as a Booster in Adults in Australia - Mongolia, Indonesia, Australia Coronavirus (MIACoV).

Tozinamrean is a single-stranded, 5'-capped messenger RNA (mRNA) produced using a cell-free in vitro transcription from the corresponding DNA templates, encoding the viral spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS\_CoV-2). A standard dose will be administered on day 0 of the study.

Tozinamrean is a single-stranded, 5'-capped messenger RNA (mRNA) produced using a cell-free in vitro transcription from the corresponding DNA templates, encoding the viral spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS\_CoV-2). A fractional dose (15mcg) of the intervention will be administered on day 0 of the study.

"Elasomeran is a single-stranded, 5'-capped messenger RNA (mRNA) produced using a cell-free in vitro transcription from the corresponding DNA templates, encoding the viral spike (S) protein of SARS-CoV-2).~A single standard dose (50mcg) of the intervention will be administered on day 0 of the study."

"Elasomeran is a single-stranded, 5'-capped messenger RNA (mRNA) produced using a cell-free in vitro transcription from the corresponding DNA templates, encoding the viral spike (S) protein of SARS-CoV-2).~A fractional dose (20mcg) of the intervention will be administered on day 0 of the study."