Yes, this is true if the pill hasn't had enough time to digest into your system. If you throw up up to about 2 hours after taking your pill you most likely threw most of the pill up, therefore making it as if you didn't take a pill at all that day. Antibiotics also make bc less effective, so make sure you u use at least a condom if your on meds, as soon as you go off the meds you are fully protected once again. Hope this helped.