I am not a doctor disclaimer...
Depends who you ask, we are in a liminal phase. It also depends on your goal. If you are fully vaccinated, and not old/immune compromised, you have excellent protection against severe cases, or death. Booster shots would be to reduce transmission (definitely) and reduce odds of contracting long covid (likely, but not enough data to say yet).
Personally, I think the rollout is far too slow, but I took a lot of shit for saying they were inevitable back in June. I understand the CDC is working on a much slower timeline and waiting for concrete data, with larger sample sizes, while I was working off probabilities. This is actually much faster for them to come around than I was expecting.
Again, just my personal opinion. I think people with Pfizer need to be getting that booster before month 6, definitely by 6. If I was a teacher, or clinician, I would not wait for the CDC. I would get my antibody levels checked and take a booster if low. I understand it goes against the CDC currently. I expect they will change it in the near future. Biden mentioned 5 months a day or so ago. I want to stress again though, I'm not a doctor and this is not medical advice. I recommend talking it over with your doctor.
I think Moderna is good through at least 6 months, but we don't know how long yet. I've been assuming ~7 months against Delta, but that's a hunch and I don't have any data to back it up yet.
I got my second Moderna at the beginning of April and have not yet gotten a booster. I wear an N95 and have kept my exposures low.
In the meantime, mask up and get your antibodies checked with the UT study. They'll give you some idea of rough protection level.