evidence: Vaccine clinical trials for a new candidate vaccine showed that vaccines very significantly reduced COVID-19 in people who were vaccinated, compared to a control group of people who did not receive the vaccine, through a reduction in numbers of laboratory confirmed SARS-CoV-2 infections. Since the population-wide roll out of COVID-19 vaccines commenced in December 2020, a significant number of effectiveness studies have been published in refereed international medical journals. The population wide effectiveness data have been in line with the findings of the clinical trial results and shown high effectiveness against infection and even higher effectiveness against serious illness, hospitalisation or death from COVID-19 infection. Progressive waning of the effectiveness of one or two doses, particularly against mild infection and against the SARS-CoV-2 Omicron variant has emphasised the importance of a third booster vaccination.