Some seven-thousand nursed have volunteered to give emergency shots to Coloradans in case of a small pox attack. Under the state's emergency plan, once the disease is detected a 7-4-7 airliner would bring enough vaccine to inoculate hundreds of thousands of people within 24 hours. Those closest to the victims would be vaccinated first but health officials would probably also decide to vaccinate a whole town or county. If so, people will be told to gather in a gymnasium or at a fairgrounds _ not at a hospital. The plan depends on a decision President Bush will make in the next few months: whether to call for vaccination-after-outbreak ora pre-outbreak vaccination program for all 280 million Americans.