脊髓灰质炎是发展中国家的一个重要卫生问题,但应用口服脊髓灰质炎疫苗预防存在严重困难。此疫苗仅有少数发展中国家能够生产,需要从外地长途运输,保持冷藏才 Polio is an important health problem in developing countries, but there are serious difficulties in using oral polio vaccine to prevent it. This vaccine is only available in a small number of developing countries that require long-distance transport from the field to keep refrigerated