On 28 July 1972, SEP Chief DA Henderson designated September 1972 as the beginning of the "final phase" of the smallpox eradication programme. Its objective was to reduce the number of cases to zero — "Target Zero".
Before the 1967 Smallpox Eradication Programme, the "success" of an eradication programme was measured as the proportion of the population apparently vaccinated successfully. The plan drafted in 1966 for WHO's Director-General by Henderson and Dr Charles Cockburn states unequivocally that "the ultimate measure of any eradication programme is its success in reducing the number of cases to zero." Further, "each case that occurs suggests the possibility of flaws in the programme. An outbreak, however small, demands a full critical review with appropriate revisions of the program."
Under "Target Zero", every case or suspected case of smallpox represented a potential failure. Every suspect case of smallpox would be dealt with as a public health emergency. Containment measures would be promptly and effectively carried out. In addition, an active search for cases would be required in many areas.
"Target Zero" became the programme's mantra. "Target Zero" T-shirts and bumper stickers were produced. The symbol of participation in the SEP, a small pin called the "Order of the Bifurcated Needle", was a bifurcated needle bent into a "zero" shape.
Order of the Bifurcated Needle, bronze, David Henderson
Target Zero — Progress Reports were issued approximately every 4 weeks from December 1972 through March 1976. The interruptions during 1975 reflect a crisis in the Bangladesh programme. Henderson "commuted" to Bangladesh from Geneva, spending 2-3 weeks there every month.
| 1972 | 1973 | 1974 | 1975-76 | ||||
|---|---|---|---|---|---|---|---|
| 16 Jan 1973 | Report No. 3 | 16 Jan 1974 | Report No. 18 | 7 Jan 1975 | Report No. 29 | ||
| 2 Feb 1973 | Report No. 4 | 11 Feb 1974 | Report No. 19 | ||||
| 27 Feb 1973 | Report No. 5 | ||||||
| 19 Mar 1973 | Report No. 6 | 11 Mar 1974 | Report No. 20 | ||||
| 2 Apr 1973 | Report No. 7 | 11 Apr 1974 | Report No. 21 | ||||
| 17 Apr 1973 | Report No. 8 | ||||||
| 8 May 1973 | Report No. 9 | 13 May 1974 | Report No. 22 | ||||
| 5 Jun 1973 | Report No. 10 | 14 Jun 1974 | Report No. 23 | 2 Jun 1975 | Report No. 30 | ||
| 28 Jul 1972 | Sep 1972: Beginning of the "final phase" | 20 Jul 1973 | Report No. 11 | 31 Jul 1974 | Report No. 24 | 11 Jul 1975 | Report No. 31 |
| 14 Aug 1973 | Report No. 12 | ||||||
| 31 Aug 1973 | Report No. 13 | 29 Aug 1974 | Report No. 25 | ||||
| 28 Sep 1972 | Progress and plans — The Final Phase | 25 Sep 1973 | Report No. 14 | ||||
| 22 Oct 1973 | Report No. 15 | 1 Oct 1974 | Report No. 26 | 27 Oct 1975 | Report No. 32 | ||
| 1 Dec 1972 | Report No. 1 | 19 Nov 1973 | Report No. 16 | 5 Nov 1974 | Report No. 27 | ||
| 21 Dec 1972 | Report No. 2 | 17 Dec 1973 | Report No. 17 | 9 Dec 1974 | Report No. 28 | 22 Mar 1976 | Report No. 33 |