Analysis of the records of instances in which non-immune persons contracted yellow fever notwithstanding vaccination shows that the onset of disease occurs soon after vaccination, the longest period being 13 days. Since the average incubation period in yellow fever is 6 days, it seems that infection must have taken place in some instances during the period while protection was developing. These instances led to a study of the possibility of immediate protection by means of the anti-icteroides serum. It had already been shown that the immune serum protects at once against experimental Leptospira icteroides infection, but it remained to determine how long the protection would last. Guinea pigs were given different quantities of the immune serum and subsequently injected, at various intervals, with a virulent strain of Leptospira icteroides. Complete protection enduring 5 days was obtained with as minute a quantity of serum as 0.002 cc. per 1,000 gm. of body weight. After 5 days, however, the immune substance rapidly diminished, and to keep the animal protected for as long as 10 days it was necessary to give 100 times as much, or 0.2 cc. For a man weighing 80 kilos, 0.16 cc. (0.002 x 80) would theoretically be sufficient to protect for at least 5 days, 1.6 cc. for 7 days, and 16 cc. for 10 days. This temporary protection may be a valuable antecedent to that furnished by vaccination, since the final effect of the latter cannot be expected until at least 9 to 10 days have passed.
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机译：对非免疫人员接种疫苗后仍染黄热的实例记录的分析表明，接种疫苗后不久便发病，最长为13天。由于黄热病的平均潜伏期为6天，因此似乎在某些情况下必须在发展保护的过程中发生感染。这些情况导致了对通过抗类胡萝卜素血清进行即时保护的可能性的研究。已经表明免疫血清可立即保护免受实验性钩端螺旋体感染，但仍需确定保护作用能持续多长时间。给豚鼠提供不同量的免疫血清，然后在不同的时间间隔内注射强毒的黄喉钩端螺旋体菌株。只需5分钟即可获得0.002 cc的血清，可提供长达5天的完全保护。每1,000克。体重然而，在5天后，免疫物质迅速减少，为了使动物受到保护长达10天，有必要给予100倍或0.2 cc。对于重80公斤的人，0.16 cc。 （0.002 x 80）理论上足以保护1.6 cc至少5天。持续7天和16毫升。持续10天。这种临时保护可能是接种疫苗所提供的有价值的先决条件，因为只有经过至少9到10天才能预期接种的最终效果。
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