Based on what data do you come to that conclusion?
The vaccination rate of a country is not correlated with its covid infection rate:
https://link.springer.com/article/10.1007/s10654-021-00808-7
And after 3 months of being fully vaccinated, people are just as likely to spread the virus as unvaccinated people:
https://www.nature.com/articles/d41586-021-02689-y
From the article:
> Unfortunately, the vaccine’s beneficial effect on Delta transmission waned to almost negligible levels over time. In people infected 2 weeks after receiving the vaccine developed by the University of Oxford and AstraZeneca, both in the UK, the chance that an unvaccinated close contact would test positive was 57%, but 3 months later, that chance rose to 67%. The latter figure is on par with the likelihood that an unvaccinated person will spread the virus.