EAVE II logo

BNT162b2 and ChAdOx1 nCoV-19 Vaccinations, Incidence of SARS-CoV-2 Infections and COVID-19 Hospitalisations in Scotland in the Delta era

March 2022: Research published in the Journal of Global Health looks at patterns of COVID-19 disease and hospital admissions in Scotland when the Delta variant was most common.

BNT162b2 and ChAdOx1 nCoV-19 Vaccinations, Incidence of SARS-CoV-2 Infections and COVID-19 Hospitalisations in Scotland in the Delta era

Shah SA, Robertson C, Rudan I, et. al.

Read the paper

Published online March 26, 2022

Available via The Journal of Global Health (online): https://doi.org/10.7189/jogh.12.05008

Summary in Plain English

The Delta variant, also known as B1.617.2, became the most common strain of coronavirus (SARS-CoV-2) in Scotland on 19 May 2021.

This variant is known to cause more severe disease than other variants, like Alpha and Omicron.

There have also been reported cases of people feeling unwell with Delta infections, and sometimes needing hospital care, even after having two vaccine doses.

Why did we carry out this work?

In previous studies, we have shown that COVID-19 vaccinations are safe and effective against infections caused by the Delta variant.

Read the publication summary on our website

However, it is also important to continue to monitor infections and hospital admissions over time, in terms of people’s vaccination status.

This helps us to understand the impact of the pandemic on the NHS when most of the adult population has been offered a vaccine. It can also help with prioritising future vaccine rollouts.

We wanted to look at how the number of people who were ill or admitted to hospital with COVID-19 changed over time, as more people became vaccinated during the Delta phase of the pandemic. This included looking at different groups of people, such as different ages and those with existing health conditions.

What data did we use?

We looked at data from 1 May 2021 – 23 October 2021, when the Delta variant was widespread in Scotland.

Through the Early Pandemic Evaluation and Enhanced Surveillance (EAVE II) project, we were able to link multiple, depersonalised, datasets for almost all the Scottish population, in near-real time.

Using this linked data, we were able to keep record of how a person’s vaccination, testing and hospitalisation status changed daily or weekly. We analysed data for adults aged 20 and over.

This included data on:

  • COVID-19 vaccinations: Pfizer-BioNTech (BNT162b2) and Oxford-AstraZeneca (ChAdOx1);
  • RT-PCR testing (‘Reverse transcriptase polymerase chain reaction’);
  • Hospital admissions and deaths;
  • Personal circumstances like age, sex, location, and health history.

Here, we tracked people’s data from the start of the study period (1 May) until either the end of the study period (23 October), or the day of their death.

In this study, we defined a “COVID-19 hospitalisation” as when a person was admitted to hospital within 14 days of testing positive by RT-PCR,  or testing positive within a day of being admitted. 

We also defined someone as being “fully vaccinated” if they had received their second vaccine dose before the end of the study period.

Find out more about EAVE II

Find out more about: What is PCR?

What did we find?

We examined data for over 4.1 million people during the study period. During this time we recorded 407,405 people with COVID-19, and 10,441 COVID-19 hospitalisations.

Vaccination status

At the beginning of the study period, the majority (80.0%) of people aged 80+ were fully vaccinated, whereas:

  • 71.8% of 60-79 year olds had received one vaccine dose
  • 56.7% of 40-59 year olds had received one vaccine dose
  • 76.9% of 20-39 year olds were  unvaccinated.

However, by the end of the study period (23 October 23, 2021) the majority of people in each age group were fully vaccinated:

Age Group Percentage of people who were fully vaccinated
20-39 68.6%
40-59 88.3%
60-79 95.5%
80+ 95.7%

Table 1: The percentage of each age group that were fully vaccinated by the end of the study period, 23 October 23, 2021

We also found that people who were considered high risk (aged 80+, or had 2 or more risk conditions) mainly received the Oxford-AstraZeneca vaccine.

Infections and COVID-19 hospital admissions

Overall, our results showed that people who were fully vaccinated with either the Pfizer-BioNTech or Oxford-AstraZeneca vaccine had fewer SARS-CoV-2 infections than people who were unvaccinated during the Delta era in Scotland.

However, we also found that the number of people being admitted to hospital with COVID-19 stayed much higher in older age groups compared to younger ones.

Interpreting the results

The data from our current study cannot be used to tell which of the two vaccines, Pfizer-BioNTech or Oxford-AstraZeneca, offers the better protection against the Delta variant.

This is because the majority people thought to be at high risk of being very unwell with COVID-19 had the Oxford-AstraZeneca vaccine. This includes people aged 80+.

Also, people who were considered most at risk received their vaccines earlier in the vaccination rollout than other people who were less vulnerable. This means the level of immune protection offered by the vaccines may have gone down over time.

Why is this study important?

Our data shows that the number of SARS-CoV-2 infections and COVID-19 hospitalisations were consistently higher in people who were unvaccinated than those who were vaccinated, during the Delta era.

This study adds to the pool of research which shows that vaccines are effective in helping to address the impacts of the COVID-19 pandemic.

It also gives us a helpful, overarching description of the impact of vaccinations on SARS-CoV-2 infections and COVID-19 hospitalisation in Scotland throughout the Delta era.


This plain English summary was created with the support and feedback of the EAVE II Public Advisory Group (PAG). This particular article was reviewed by PAG members Eve S and Sandra J.

To learn more about the PAG, see: Our EAVE II Public Advisory Group (PAG) | The University of Edinburgh