Coronavirus (Covid-19) Infection Survey – Antibody and Vaccination Data For Northern Ireland

Date published: 13 January 2022

The findings set out in this report relate to antibody estimates for Northern Ireland for the week beginning 20 December 2021 and vaccination estimates for the week beginning 13 December 2021.

This report is part of the series of Northern Ireland publications from the COVID-19 Infection Survey. Further information can be found on the Department of Health website.

Key Findings

Due to the relatively small number of people who tested positive for antibodies within our sample, credible intervals are wide and therefore results should be interpreted with caution.

• In Northern Ireland, it is estimated that 97.4% of the adult population (95% credible interval: 96.0% to 98.2%) would have tested positive for antibodies against SARS-CoV-2 on a blood test in the week beginning 20 December 2021, suggesting they had the infection in the past or have been vaccinated.
• In the week beginning 20 December 2021, the percentage of adults testing positive for coronavirus (COVID-19) antibodies remained high among all age groups in Northern Ireland. The percentage of adults aged 16 to 69 testing positive for antibodies ranged from 95.9% to 98.4%; for those 70 years and over it was 98.9% (95% credible interval: 97.5% to 99.6%).
• For the first time, based on academic research we present the percentage of adults with antibodies to SARS-CoV-2 at or above a higher antibody threshold, which provides greater protection against COVID-19 following vaccination. Academic research on antibody thresholds using data from when the Delta variant was the dominant strain indicate that a higher threshold of antibodies is needed to provide protection from new COVID-19 infections for those who are vaccinated. It is estimated that 90% of the NI population had antibodies at or above the higher threshold with the booster programme likely leading to the rapid increases in antibodies above this threshold seen in older age groups.
• The survey provides an estimate of the percentage of people that have been vaccinated however it should be noted that the figures are based on self-report and may differ from official figures which are a more precise count of total vaccines issued.
• The survey estimates allow for additional analysis of vaccination information with other characteristics, such as testing positive for antibodies.
• The survey shows the estimated percentage of adults who reported they have received three or more COVID-19 vaccinations has increased rapidly since September 2021, in line with the vaccine programmes.