After Hakuō had delivered the vaccine to Fukui and set up his clinic, he immediately offered to share it widely with medical specialists in nearby domain territories. He probably did so for the same reason he had accommodated his colleagues in Osaka: because he hoped to create a reservoir and build a professional vaccinators' network with common goals and standards, one that could share knowledge, suppress competitors, and even challenge domain administrators if necessary. Besides, as noted, Hakuō was driven by a strong commitment to eradicate smallpox from the Japanese islands as a whole. 

Hakuō wanted to ensure that only trained specialists performed vaccinations. He feared that parents would otherwise lose confidence in the treatment and hesitate to make their children's bodies available. A few weeks after his return to Fukui (1850, 1/17), he wrote to specialists of Dutch medicine in towns and territories in the surrounding Hokuriku region with an offer to share the vaccine. Physicians from Fuchū (a subfief of Fukui domain) had already received a transmission upon Hakuō's reentry into Fukui. In subsequent weeks, colleagues from Toyama (Toyama, a branch domain of Kaga), Kanazawa (Kaga domain), Tsuruga (Obama domain), Sabae (Sabae domain), Ōno (Ōno domain), Daishōji (a branch domain of Kaga), Maruoka (Maruoka domain), Kanazu (Fukui domain), and Katsuyama (Katsuyama domain) came to Fukui with children in tow who would carry vaccines home in their bodies. Before vaccination, these physicians had to receive instructions and sign an oath at the domain office that they would observe tenets of medical ethics and all technical requirements.

The newly minted vaccinators joined the vaccinators' society (sha) and formed chapters (so-called shachū) in their respective towns and territories. Initially, each chapter had only a handful of members, but together, these chapters formed a professional organization that transcended domain borders and provided retransmissions. Other functions of the organization included the sharing of information and suppression of uncontrolled transmissions. An autonomous, self-regulating network of medical professionals was thus taking shape without much prodding from domain governments. At the same time, effective collaboration with domain leaders was one of the network's most important functions.

In Osaka, Ogata Kōan, the head of the local vaccination clinic who had received a transmission from Hakuō in 1849, kept a similar record of physicians with whom he had shared the smallpox vaccine, up until 1869. His list included 168 transmissions, mostly to physicians in Osaka and surrounding provinces, and some based in places as far away as Edo and Nagasaki [Osaka no jotōkan].