FOI Ref: FOI/2023/4881
You asked
I am currently looking for data for early in the vaccination programme. I would like to know what the definition of "Unvaccinated" is in the INS dataset named "Deaths involving COVID-19 by vaccination status, England: deaths occurring between 1 January 2021 and 31 May 2022"?
Also, specifically, I would like to know how the vaccination status is derived for a patient who died. For example, how is it worked out from the NHS number and the National Immunisation Management System (NIMS) IMS dataset for example.
I am looking at whether the 14 days prior to vaccination are taken into account as in the "ICNARC report on COVID-19 in critical care: England, Wales and Northern Ireland 6 July 2021" where it is stated: "Based on knowledge that it takes 2-3 weeks following each vaccination to reach maximum effectiveness, vaccination status was defined (prior to analysis) as: Unvaccinated either no linked vaccination record in NIMS or first dose of vaccine received within 14 days prior to the positive COVID-19 test.
We said
Thank you for your enquiry.
Vaccinations are not recorded on the death certificate when a death is registered, therefore our publication Deaths involving COVID-19 by vaccination status uses mortality data with data linkage to the National Immunisation Management System.
The data for the age-standardised mortality rates (ASMRs) are created using the Public Health Data Asset (PHDA), a linked dataset combining the Census, the General Practice Extraction Service (GPES) data for coronavirus (COVID-19) pandemic planning and research, and the Hospital Episode Statistics (HES). We linked vaccination data from the National Immunisation Management Service (NIMS) to the PHDA based on NHS number.
The PHDA dataset contains a subset of the population and allows for analyses to be carried out that require a known living population with known characteristics (such as for ASMRs by vaccination status) and the use of variables such as health conditions and census characteristics.
The definition of unvaccinated used in our Deaths by vaccination status publications does not include people who had any vaccine for any length of time. We have separate categories for people who have received a vaccination within the past 21 days.
More information can be found in the following link to our methodology article: Methodology article.
If you would like to discuss your enquiry further, please contact health.data@ons.gov.uk.