Interesting figures from Iceland. Why is the infection rate among fully vaccinated skyrocketing?

Around December 20th the infection rate among fully vaccinated adults has increased by 556% and by 179% among the unvaccinated.


This is a sharp shift in the trend, away from an approximately double infection rate among the unvaccinated against vaccinated for a long period. For those with a booster the shift is even bigger, 1200%.


What might be the explanation for this? Is there a reason to expect a surge in hospitalisations among the vaccinated will follow?


See the data:

https://www.covid.is/data