Summary of Chapter 11:
Smallpox vaccine and vaccination in the Intensified Smallpox Eradication Programme

By the time the Intensified Smallpox Eradication Programme (1967-1980) was launched, vaccination was already widely practiced across the world. However, many endemic countries still lacked a high-quality, heat-stable vaccine that could be effectively distributed under challenging environmental conditions. This chapter discusses the challenges, improvements, and innovations in smallpox vaccine production, distribution, and administration, which played a key role in achieving global eradication.

Vaccine requirements for the intensified programme

The success of the eradication programme depended on the availability of potent, heat-stable vaccines. Initially, vaccine quality varied significantly, and WHO faced major obstacles, including:

  • Shortages in vaccine supply due to limited global production.
  • Inconsistencies in vaccine quality, with some batches lacking potency or heat stability.
  • Logistical challenges in distribution, especially in tropical regions.

To address these issues, WHO established quality control mechanisms, ensuring vaccines met international standards before being used in the field.

Development of improved vaccines

Efforts to improve vaccine quality included:

  1. Survey of Vaccine Producers (1967) – WHO evaluated vaccine production facilities worldwide to standardize manufacturing practices.
  2. Freeze-Dried Vaccine Production – Unlike earlier liquid vaccines that lost potency quickly, freeze-dried vaccines remained stable for months in high temperatures.
  3. Strains of Vaccinia Virus – Different strains were used, but the Lister strain became the most widely adopted due to its strong immune response and stability.
  4. Heat Stability and Potency Testing – WHO developed rigorous heat-stability tests to ensure vaccines could survive distribution in remote areas.

New vaccination techniques

To improve vaccine delivery, new tools and techniques were introduced:

  • Bifurcated Needle – A simple and cost-effective device that improved vaccine uptake and reduced wastage.
  • Jet Injectors – Used for mass vaccination campaigns, particularly in areas with high population density.
  • Modified Scarification Methods – Improved techniques were developed to reduce contamination and maximize vaccine effectiveness.

Ensuring vaccine availability

WHO coordinated vaccine donations from multiple countries, with the USSR, the USA, and European nations providing millions of doses. Over time, production in endemic countries increased, making vaccine supply more sustainable.

Final phase: Discontinuation of vaccination

Following smallpox eradication in 1980, routine smallpox vaccination was discontinued worldwide, except for military personnel and laboratory workers handling variola virus. However, research on vaccinia virus as a vector for other vaccines has continued, demonstrating its potential in combating other infectious diseases.

Conclusion

The success of smallpox eradication was directly linked to improvements in vaccine quality, production, and delivery methods. WHO’s efforts in ensuring vaccine potency and stability, combined with innovative vaccination techniques, allowed for the complete elimination of smallpox, making it one of the greatest achievements in global public health.