Age is the most important risk factor associated with deaths in individuals who have received COVID-19 booster shots, a new study has found.
Researchers from the Office for National Statistics (ONS), Public Health Scotland, the University of Strathclyde, and the University of Edinburgh conducted the study.
They noted that it has become "critical to identify risk factors associated with COVID-19 death in individuals who have completed primary vaccination and received a messenger RNA (mRNA) booster dose," due to the emergence of the Omicron variant.
"Existing evidence is based on people who have received 1 or 2 doses of a COVID-19 vaccine and were infected by the Alpha or Delta variant," researchers wrote. "Understanding which groups are at increased risk of COVID-19 death after receiving a booster is crucial for the prioritization of further booster doses and access to COVID-19 therapeutics."
Researchers said they used data from the ONS Public Health Data Asset for the study, which is a "population-level linked data set combining the 2011 Census of England and Wales and electronic health records covering 80 percent of the population of England."
The study population covered 19,473,570 UK residents aged 18 to 100 who had completed both doses of their primary COVID vaccination schedule as well as an mRNA booster shot 14 days or more prior to Dec. 31, 2021.
COVID-19 Greater Hazard for Elderly, MenThey found that there were 4,781 (0.02 percent) deaths involving COVID-19 and 58,020 (0.3 percent) deaths from other causes during the study period, with the median age of those who died from COVID-19-related deaths averaging 83.3.
Compared with a 50-year-old, the "hazard ratio" or "HR" for an 80-year-old individual was 31.3 percent, the authors said, noting that "age was the most important characteristic associated with the risk of post booster COVID-19 death."
Women were also at lower risk of COVID-19 deaths than men, the study found, with an HR of 0.52 percent; while there was an increased risk of COVID-19 death associated with living in a care home or in less wealthy neighborhoods.
When it comes to the risk of COVID-19 death and ethnicity, the authors said they found "no association" between the two, "except for those of Indian background, who were at slightly elevated risk compared with White individuals."
"Most of the QCovid risk groups were associated with an increased HR of post booster breakthrough death, except for congenital heart disease, asthma, and prior fracture," the authors wrote of their modelling they called QCovid. "Risk was particularly elevated for people with severe combined immunodeficiency (HR, 6.2; 95 percent CI, 3.3-11.5). There were several conditions associated with HRs of greater than 3, including cancer of blood or bone marrow and dementia."
The authors of the study noted that their results were limited due to the fact that they only included data for the UK population that were listed in the 2011 Census of England and Wales.
"The association between the QCovid risk groups and the risk of death were stronger in people who had received a booster and were infected by the Omicron variant compared with evidence from the Alpha and Delta period in doubly vaccinated individuals," researchers wrote. "The subpopulations with the highest risk should be considered a priority for COVID-19 therapeutics and further booster doses."