十九世纪二十年代以来,大量试验表明维生素A对体液和细胞免疫过程非常重要。流行病学调查表明,维生素A缺乏和婴幼儿的发病率、死亡率的增高有密切关系,给处于维生素A临界状况的幼儿提供维生素A,就会使感染的发病率、严重程度以及死亡率明显下降。新生儿破伤风病仍是发展中国家公共之忧,年死亡人数达750000人。一些国家 Since the 1920s, a large number of tests have shown that vitamin A is very important for humoral and cellular immune processes. Epidemiological studies have shown that lack of vitamin A and infant and child morbidity, mortality is closely related to vitamin A in children with critical conditions of vitamin A, it will make the incidence of infection, the severity and mortality significantly decline. Neonatal tetanus is still a public concern in developing countries, with an annual death toll of 750,000. Some countries