[1] For part of this time he worked on vaccine control and standardisation, an area in which he received training at the Paul Ehrlich Institute in Germany.
Under his leadership an outbreak of variola minor in the Horn of Africa during the Ethiopian–Somali war was successfully contained, and the final case of naturally transmitted smallpox occurred in October 1977.
He was also involved in formulating policies on issues including ongoing vaccination and laboratory stocks of variola virus, and in archiving WHO's data on the eradication programme.
[9] Arita was one of the lead authors, with Frank Fenner and Henderson, of the WHO publication Smallpox and its Eradication, an exhaustive 1460-page volume which was published in January 1988.
[1] He advised Morihiro Hosokawa (then governor of the Kumamoto prefecture) on the foundation of the Agency for Cooperation in International Health (ACIH) in 1990,[12] and became its chair in 1993.
[13] The ACIH aims to promote disease prevention in developing countries, and the body has organised international conferences on vaccines and other topics.
In 2006, with Fenner and Miyuki Nakane, Arita published an opinion piece in the journal Science that questioned whether it was feasible to eradicate polio globally, and suggested that control might be a preferable option.