It took only a few months—until the 7th month of 1850—for the vaccine to go extinct in Ōno domain. Ōno’s vaccinators blamed this failure on a lack of volunteers and received a second transmission from Kasahara Ryōsaku in the 11th month [“Shutō shōrei ni tsuki furegaki,” 1851, in Fukui kenshi, Shiryō-hen 7, 458–59]. But suddenly their fortunes turned. In the winter of 1850/51, Motodo, a village deep in the “southern mountains” exclave of Ōno domain, was ravaged by the smallpox virus (see the header image for a photo of the former village site, and the map below for its location). This sad event turned into an unexpected boon for Ōno’s vaccinators because it convinced skeptical villagers that the cowpox vaccine was effective at protecting children from smallpox.

In a letter to Kasahara, Ōno's domain physicians Nakamura Taisuke and Hayashi Unkei explained that the disease had spared a handful of children who had received the vaccine in the summer of 1850. According to the letter, village officials in the affected area had then begun to turn to the rural intendant to request more vaccinations and gathered about a hundred volunteers. The letter stated that townspeople and villagers had finally understood the value of the vaccine, and that “we have now escaped the trouble of searching for children to be vaccinated.” [Letter from Nakamura Taisuke and Hayashi Unkei to Kasahara Hakuō, 1851.2.25, in Kasahara, Hakushinki, 144–45] This small vaccination boom occurred two years before Fukui town experienced a similar effect in the winter of 1852/53. It was widely advertised within the domain by Ōno's domain government.

What made Motodo such a compelling test case? It was located in a remote, thinly populated valley about a day’s journey (30 kilometers) from Ōno's castle town. Apparently the three physicians had made an effort to travel to certain parts of the domain in the spring and summer of 1850 to spread the vaccine. Why Motodo was selected is uncertain, but the fact that only a handful of Motodo’s children were vaccinated suggests that most village parents had remained suspicious at the time. The village’s secluded location probably amplified the impact of the 1850/51 smallpox outbreak. It was not uncommon for smallpox to hit different parts of the same region at different points in time. In addition, data from other parts of Japan suggest that remote villages were not visited by the virus as frequently as other communities, but tended to experience higher fatalities when the virus did strike because there were many cohorts of newborns who had failed to build immunity [Jannetta, Epidemics and Mortality in Early Modern Japan, 1987, p.].

Motodo’s success story does not mean that Ōno’s physicians had solved the problem of uncooperative parents. In the early 1850s there were only three physicians in the domain who were capable of administering vaccinations, and villages like Motodo had to have regular access to vaccinate every newborn, either by bringing their children to the castle town or by having vaccinators visit their valley once with carrier children in tow and then a second time after seven days, as described in the pathway on village relay in Fukui domain. In the winter, such visits would have been particularly daunting because mountain roads were blocked by heavy snow. Moreover, their optimism in 1851 notwithstanding, Ōno’s vaccinators had not yet convinced the local people of the benefits of their treatment.