How long does it take for yaz birth control pill to become effective in preventing pregnancy?

i started taking the birth control pill yaz today and am so far not having any side effects like nausea...thank god lol. my question is, how long does it take for the pill to become effective in preventing pregnancy? i always thought it was one month, but the info packet that came with the pills said to use a back up method for a week. and even though its my first day taking the pills, can i still have side effects like nausea and breast tenderness in the next few days?How long does it take for yaz birth control pill to become effective in preventing pregnancy?
The info packet is right- one week.





Side effects like nausea and tenderness shouldn't last longer than one or two weeks, but other effects like weight gain, irritability, and mood swings might last as long as you're taking the pill.