C_K,
As always your efforts are highly appreciated by me as well. I'm sorry to hear you have Covid, but happy to here you have only mild complaints.
As for getting Covid after being vaccinated: None of the available vaccines covers a full 100% For the Delta version the mRMA vaccines like Moderna and Pfizer are expected to protect 98% of the vaccinated people. For the vector type of vaccines this is less. For the AstraZeneca vaccine the expected percentage is 92% and for the Johnson & Johnson vaccine they expect even a lower percentage. A positive effect for the people who are infected after being vaccinated is that you become less ill. Hospitalisation is a very rare thing for this group.
The older you get the less good your immune system will work, but it is also harder to activate with a vaccine. So for us old farts the vaccines are simply less effective, but they do keep us out of serious trouble.
Get well and looking forward to fly the DH.9a
Huub