What Worked
Five things did the work. The first one is not what the programme was designed around, and it was found by someone running out of vaccine rather than by anyone planning a strategy.
Surveillance and containment
Find every case, then vaccinate the people around that case rather than the whole population. In eastern Nigeria during a vaccine shortage, Bill Foege vaccinated only family members and close contacts of patients, put other contacts at risk under surveillance, and the cluster of outbreaks there stopped. [3] The method was published in 1971 as selective epidemiologic control. [1] It requires weekly reports of cases from all health facilities and containment teams that go out to outbreaks. [24]
The reason this works and mass vaccination struggles is arithmetic about uncertainty. Mass vaccination has to reach a whole population, most of which will never be exposed. Containment only has to reach the people who actually are. Against a disease with no animal reservoir, every chain runs through someone you could find. [2]
Active search instead of passive reporting
Waiting for cases to be reported did not find them. In India, reports moved up through a hierarchy of offices, delayed at each stop and sometimes changed on the way. [24] The programme replaced that with searching. By late 1974 in India some 33,000 district health personnel and more than 100,000 additional field workers were searching house to house across 575,721 villages and 2,641 cities, covering every one of the country's 100 million households in a six-day period each month. [4] Breman puts the peak at more than 150,000 field workers. [3] Both figures are sourced and they disagree, so both stand.
The bifurcated needle
A sewing machine needle with its eye bifurcated holds a drop of vaccine between the prongs when dipped in the bottle. It cut the vaccine used per person and needed little training. Success rates were above 95%. [3]
Endemic countries paying for most of it
The intensified programme cost about US$300 million between 1967 and 1977, and two thirds of that came from the endemic countries themselves rather than from donors. [7]
Certification by people who did not run the programme
Eradication was not declared by the programme that achieved it. An independent scientific commission certified it in December 1979, using special certification procedures in the 35 countries where the disease had been endemic and in 44 others judged at particular risk. [2] The World Health Assembly accepted that conclusion in May 1980. [5]
Indian search staffing, late 1974 [4]
133 K
Vaccination success rate with the bifurcated needle [3]
>95%
Endemic countries given certification procedures [2]
35
Further countries certified as at special risk [2]
44
A warning about reading this page. Four of these five are cheap, unglamorous and organisational: find the cases, go to them, use less vaccine, let someone else check your work. None of them is a scientific breakthrough. The vaccine was roughly two centuries old when the programme that used it succeeded. If you take one thing from this slate to another problem, it should probably not be the technology.