United Nations Rich countries should make more vaccines available to poorer nations where the H1N1 virus is starting to hit, United Nations health officials said. They said increased readiness for swine flu was needed in developing countries with weaker medical systems and with large, young populations, who are most vulnerable to the disease. Some countries, such as the United States, Brazil and France, have agreed to make 10 percent of their national vaccine stockpile available to developing countries.