Prior to 2151, Earth ships had been operating within 90 light years of the Sol system. In that year, the Enterprise became the first ship to travel further than this distance. (ENT: "Two Days and Two Nights")
According to the Star Trek: Star Charts (pgs. 36, 44, "United Federation of Planets I"), Vega IX (or Vega Colony) was, in the mid-22nd century, an important trading world on the Earth trade routes. Vega colony traded with Draylax and Earth in the mid-22nd century. In 2378, Vega IX was located in Federation space. The planet was a destination on the major space lanes. It was a Federation member.