The chances of being reinfected are still extremely low, the fact that there are a few reinfections doesn't change that. Knowing that you still have antibodies means the chances of reinfection are basically zero.
We can consider two different extreme possibilities:
A. 99.99% of people have lifelong immunity after a covid infection, but a tiny percent don't, and can get reinfected.
B. 0% of people have lifelong immunity, and they lose immunity about 6-12 months after the first infection.
For the two scenarios, the percent who lose immunity each month would look something like this:
A B
Sept 0.1% 0.1%
Oct 0.1% 2%
Nov 0.1% 14%
Dec 0.1% 34%
Jan 0.1% 34%
Feb 0.1% 14%
Mar 0.1% 2%
April 0.1% 0.1%
When we first see a tiny number of reinfections, we can't determine which of the two hypotheses is correct, whether re-infections are very unlikely (A) or very likely (B). We would expect to see only a few re-infections at this point in either scenario. Only in a few months will we know which is more likely true.
Of course, losing immunity is not the same as reinfection, since some will take precautions to avoid reinfection.