This is a retrospective cohort study to assess the real world effectiveness of the Oxford/AstraZeneca COVID-19 vaccine in England. The study is using linkage of the English national databases on COVID-19 vaccination, testing, medical records, hospitalization, and death.

The United Kingdom (UK) is one of the first countries that introduced a mass vaccination campaign for COVID-19 and vaccination of the adult population first focused on the oldest age groups, their carers and health care workers (JCVI, 2020). Three COVID-19 vaccines were licensed and are being used including the Moderna, the BioNTech/Pfizer, and the Oxford/AstraZeneca vaccines. Vaccination with the BioNTech/Pfizer vaccine started in December 2020 and the Oxford/AstraZeneca vaccine started in early January 2021. This study is to primarily assess the effectiveness of the Oxford/AstraZeneca COVID-19 vaccine. Given the known high efficacy of the mRNA vaccines in randomized controlled trials (RCTs) and real-world evidence studies, the study aims also to evaluate the vaccine effectiveness (VE) of other COVID-19 vaccines as a validation of the study's methods. On 16 September 2021 it was announced that Booster doses would be introduced in the UK to address vaccine waning and for groups with a suboptimal response. Little is known about health care resource utilisation (HCRU) and health care costs for those who have had COVID-19 or by individual clinical risk group. The RAVEN study is a retrospective cohort study to assess the real-world effectiveness of the Oxford/AstraZeneca COVID-19 vaccine in England. The study is using linkage of the English national databases on COVID-19 vaccination, testing, medical records, hospitalization, and death. Analyses will examine the effectiveness of one and two doses, and booster or other additional doses if applicable. This study's extension (October 2021) adds a more detailed exploration of VE in risk groups and an evaluation of the HCRU by people with COVID-19 compared with those who are vaccinated.

Inclusion Criteria:

• Eligible for any COVID-19 vaccination based on age at index date
• Have continuous data coverage for the COVID-19 infection datasets
• Have continuous data coverage in other linked databases for a minimum of 12 months prior to the index date

Exclusion Criteria:

• People with a history of COVID-19 infection (confirmed by reverse transcriptase polymerase chain reaction (RT-PCR) or not) prior index date

12 years old or older population in England who met inclusion criteria