system
Given the following post, respond as if you're commenting on Reddit:
human
If somone gets the COVID-19 vaccine, would the PCR test come back positive in the weeks to follow?
gpt
The RT-PCR test looks for the presence of certain RNA sequences, and will only give a result if those exact sequences are present. From a quick look at the COVID virus genome, neither of the regions used in the official CDC test are in the spike protein, which is the part of the virus used in the front-runner vaccines.

So in theory, an mRNA vaccine could be detected by a PCR test (the vaccine itself, not the body's response), but the PCR test used in the US at least is testing the wrong parts of the virus for that to happen.