As the UK implemented mass COVID-19 vaccination programmes it became essential to know how much protection they gave from severe outcomes and for how long. Researchers carried out a study across all four UK nations which showed a relatively rapid waning – providing vital information for policymakers.


There was an urgent need to understand how quickly the effectiveness of each vaccine dose waned. Answering this question was difficult as many people had their follow-up cut short by an additional dose of vaccine or the end of the study period.


A research team (part of the EAVE II programme) analysed the effectiveness of COVID-19 vaccines in preventing hospitalisation or death, pooling data from four nations and 12.9 million individuals.

This pooling maximised the amount of relevant patient data that was available, giving the study a great deal of statistical power.

The research (part of HDR UK’s Data and Connectivity National Core Study) was the first of its kind in this country. There were challenges in making the data (covering 8 December 2020 to 30 June 2021) research-ready as each nation had its own approach to data collection and formatting.

Patient confidentiality was a priority. A novel approach was taken which allowed the researchers to do combined work on data without sharing any patient records.


The findings were published in Waning of first- and second-dose ChAdOx1 and BNT162b2 COVID-19 vaccinations: a pooled target trial study of 12.9 million individuals in England, Northern Ireland, Scotland and Wales (International Journal of Epidemiology, February 2023).

Strong evidence was found of waning in protection against severe outcomes from Doses 1 and 2 of Oxford–AstraZeneca as well as Dose 1 of Pfizer–BioNTech (reaching zero after two to three months and then going negative). For Dose 2 of Pfizer–BioNTech protection remained higher for longer.

Lead author Dr Steven Kerr, Senior Research Fellow at the University of Edinburgh Usher Institute, Centre for Medical Informatics, says this could be because vaccinated people believed themselves to be protected, and behaved in ways which put them at greater risk. It could also be an unavoidable consequence of the fact that immunological protection offered by the vaccine is not long-lasting.

Another impact has been to help address questions over the goals of the vaccination programme.

Dr Kerr said: “When you have a vaccine with a relatively short period of effectiveness against an endemic disease, the main utility of mass vaccination is flattening the curve.

“If you time vaccination campaigns correctly – like we try to do with flu – then you can spread the caseload. That means the level of healthcare provided to people who get COVID will not suffer unnecessarily at any time.”

Dr Kerr has been awarded a Chancellor’s Fellowship to further develop the methodology used in the study.

He said: “I am looking at ways to put in place the technology and infrastructure that allows these sorts of studies to be done using multiple datasets but with zero data sharing. It is excellent for patient confidentiality and means research can take place that wouldn’t otherwise be possible.”

What the Impact Committee said:

The committee described the paper as “excellent”. They praised it for looking at all four nations, for its methodology, scale and high impact on an important policy issue.


Email steven.kerr@ed.ac.uk