Since Delta hit the scene, vaccine immunity from being infected lasts about 3 months. After this time, the vaccine immunity from being infected becomes almost ineffective.
Vaccines still reduce hospitalization and death rates, but they only offer short-term protection against being infected due to waning immunity.
Whenever a country has enough vaccine to offer everyone the jab, the infections go down for a while.
However, after 3 months they just pick up again.
Germany and the Netherlands now have the fastest rise of Covid they have ever had. The UK got vaccinated first, and then cases became high again before winter. However, now they have gone down slightly- as more people get the booster jab.
It is not just the vaccine that loses its ability to prevent the vaccinated from being infected. Those that have anti-bodies from surviving past infections are also prone to getting Covid again. Data comparisons are not clear yet, but it seems both the vaccinated and unvaccinated are in the same boat.
However, some reports show that people who have been vaccinated and infected with Covid have the best immunity from future infection- but more data is needed here.