The largest study of its kind in the UK has found that of 40,393 hospitalizations and deaths from COVID-19, 7,180 could have been avoided if people had been fully vaccinated. The landmark study, conducted by Health Data Research (HDR) and the University of Edinburgh, looked at hospitalizations and deaths in England, Scotland, Northern Ireland and Wales between June 1 and September 30, 2022.

In this wide-ranging work, researchers accessed secure, anonymized National Health Service (NHS) data on everyone aged over five - around 67 million people. To address concerns about the dissemination of confidential health data, approved researchers will only have access to de-identified information and evaluate it under strict security controls.

After aggregating and unifying the analysis of data from four countries, disaggregating the population by age groups and using vaccination status as a variable, mathematical modeling revealed how much serious and fatal disease could be prevented over four months.

In the UK, the first COVID-19 vaccines were administered in December 2020, but by 2022, research showed that a total of nearly 30.5 million people (44.4%) in the four countries had not received the vaccine or had not received it on time. Researchers found that under-vaccination was associated with a higher risk of severe outcomes from COVID-19 compared with full vaccination.

"We found that undervaccination (receiving less than the recommended dose of SARS-CoV-2 vaccine) was associated with an increased risk of severe COVID-19 outcomes in all age groups studied," the researchers noted. "This is the first epidemiological analysis using personal electronic health records covering the entire UK population."

Consolidated data on vaccinated/unvaccinated people were assessed in the age groups 5-11, 12-15, 16-74 and 75 and over. The researchers found that the highest rates of under-vaccination were among younger people, men aged 5-74 and in lower socioeconomic areas. Not surprisingly, vaccination rates were highest at the beginning of the sampled data period and dropped significantly by the end of the period on September 30.

Data shows that undervaccinated children aged 5-15 are more than twice as likely to be hospitalized or die from COVID-19 as other children. The risk is about 50% higher for people aged 16-74, while those aged 75 and older are three times more likely to experience adverse outcomes.

The researchers noted: "The incidence of severe disease in younger age groups was strongly associated with undervaccination. In both ordinary and extended adjusted analyses, the results were broadly similar in each country."

While vaccines were never designed to prevent infection, there is a growing body of solid scientific evidence that they are highly effective in preventing people from being hospitalized and dying. That is, for those who are still getting vaccinated more than two years after the pandemic began.

Alan Keys, a co-author of the study and a public contributor at the British Heart Foundation's Center for Data Science (HDRUK), said: "The results provide strong validation of the benefits of vaccination."

This large data set was made possible thanks to the development of a unified and anonymized analysis framework, but the scientists hope to expand the scope of the data set to better understand other serious health care problems.

Cathie Sudlow, chief scientist at HDR, said: "The infrastructure is now in place to harness the full potential of data routinely collected across the four NHSs in the UK. We believe we can and should extend these methods to many other areas of medicine, including cancer, heart disease and diabetes, in the quest to better understand, prevent and treat disease."

The UK reports that 90% of residents over the age of 12 have received at least one vaccination by January 2022, however, data shows that the pace of vaccination with booster doses has slowed significantly.

"Large-scale data research is critical for pandemic management, allowing scientists to quickly draw policy-relevant conclusions," said co-first author Sir Aziz Sheikh, HDR UK Research Director. "COVID-19 vaccines save lives. As new variants emerge, this research will help identify and tailor public health campaigns to our community groups and regions of the country."

The research was published in The Lancet.