Even if you've been vaccinated, it's a good reminder to continue best practices to avoid contracting the virus, and to be familiar with COVID symptoms so if you experience them, you can get tested and limit spread of the virus.

It's too soon to tell if Omicron causes different symptoms than previous variants of COVID-19.

But researchers at the COVID Symptom Study have been tracking the symptoms of new COVID cases, and they report that symptoms related to the Delta variant have changed somewhat compared to earlier iterations of the virus.

They say these are now the most commonly reported early symptoms, if you're vaccinated: 

If you haven't been vaccinated, experts say your early symptoms are likely to be similar to earlier strains of COVID-19, including fever, a cough that may be severe, and body aches, along with runny nose, headache and sore throat

You really can't, experts say.  The best thing to do if you're experiencing any unusual symptoms is to get tested for COVID as soon as possible—even if you've been fully vaccinated—and to self-isolate until you know the results