In England, it is estimated that 97.5% of the adult population would have tested positive for antibodies against coronavirus in the week beginning 20 December 2021.
In Wales, an estimated 96.8% of the adult population (95% credible interval: 95.9% to 97.5%) would have tested positive for antibodies against SARS-CoV-2 in the same week.
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 in the same week.
In Scotland, it is estimated that 97.7% of the adult population (95% credible interval: 97.1% to 98.2%) would have tested positive for antibodies against SARS-CoV-2 in the same week.
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 coronavirus (COVID-19) infections for those who are vaccinated.
It is estimated that more than 88% of the population had antibodies at or above the higher threshold.
The COVID-19 vaccination booster programme was likely leading the rapid increase in antibodies above the higher threshold seen in older age groups.
