Findings from the first study to assess the impact of COVID-19 vaccination on prevention of severe illness from COVID-19 in the community found that four weeks after administration of a first dose, risk of hospitalisation was reduced by up to 85% by the Pfizer/BioNTech vaccine and up to 94% by the Astra Zeneca vaccine.
Among people aged over 80, combined results from both vaccines showed an 81% reduction in hospitalisation risk four weeks after an initial dose.
The findings are based on data gathered between 8 December and 15 February - a period in which 1.14m doses of vaccine were administered in Scotland, with 21% of the population receiving a first dose.
Around 650,000 people have received a first dose of the Pfizer vaccine, while around 490,000 had the Oxford/Astra Zeneca vaccine.
The findings come from the 'EAVE II' project, which uses patient data to track the COVID-19 pandemic and the vaccine rollout.
Dr Jim McMenamin, National COVID-19 Incident Director at PHS, said: 'These results are important as we move from expectation to firm evidence of benefit from vaccines. Across the Scottish population the results show a substantial effect on reducing the risk of admission to hospital from a single dose of vaccine.'
The latest UK data on the COVID-19 vaccination campaign show that by 20 February, 17.6m people had received a first dose of vaccine - around a quarter of the total population. The government declared last week that it had met its target of vaccinating 15m people by 15 February, covering the vast majority of those in the first four priority cohorts identified by the Joint Committee on Vaccination and Immunisation.
Lead researcher and director of the University of Edinburgh’s Usher Institute Professor Aziz Sheikh said: 'These results are very encouraging and have given us great reasons to be optimistic for the future. We now have national evidence – across an entire country – that vaccination provides protection against COVID-19 hospitalisations.
'Roll-out of the first vaccine dose now needs to be accelerated globally to help overcome this terrible disease.'
Dr Josie Murray, Public Health Scotland public health consultant lead for EAVE II, said: 'These data show real promise that the vaccines can protect from the severe effects of COVID-19. We must not be complacent though. We all still need to ensure we stop transmission of the virus.'