You can get involved in research as a premed without having a science major...the key is that you're a premed, and also taking science courses in addition to your econ work. (If you were *just* an econ major with no science coursework it's a different story.) It might be tougher to get your foot through the door, but many labs would take someone with is reliable/dependable and trainable over someone who is just doing it to fulfill a requirement. Your econ background, if it involves stats, could also be a boost if a PI is looking for someone to do data analysis in addition to other work.