An unvaccinated friend of mine has been down with covid the last few days, low fever, cough, but the worst symptom she said was terrible headache in the back of her head. After a conversation with her vaccinated sister and brother in law who she spent a lot of time with the previous week, they told her they had those same headaches for several days during that time span. So it is possible the vaccinated spreading covid to the unvaccinated is a real thing.