lessons learnt from smallpox eradication and post-eradication strategy
TRANSCRIPT
Dr. David Ulaeto
© Crown copyright 2014 Dstl
3 May 2023
Lessons learnt from smallpox eradication
and post-eradication strategy
Outline
• Variola virus and orthopoxviruses• Smallpox and its eradication• Sequestration of variola virus after eradication• Regulation of variola virus repositories & research• Emergence of related viruses
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Genus Orthopoxvirus
• Members: variola (smallpox), monkeypox, cowpox, vaccinia, ectromelia, raccoonpox, taterapox, camelpox, rabbitpox, buffalopox
• All are morphologically identical• All are immunologically related and confer protection
against other members of the genus
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Why Was Smallpox Eradication Possible?• No animal reservoir• No latent or persistent infection• Smallpox was an easily recognised disease• The vaccine was effective against all strains of
virus• Vaccine properties. Efficacy, potency, low cost,
abundance, heat stability, easy administration• WHO determination
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Smallpox Control
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Lady Mary Wortley MontaguVariolation 1721
Edward JennerVaccination 1796
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Smallpox Eradication • 1721. Variolation• 1796. Vaccination• 1801. Eradication predicted• 19th century. Vaccination spreads throughout the world
• 1950. Freeze dried vaccine developed
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Smallpox Eradication • 1959. WHO adopts Russian proposal to eradicate smallpox• 1967. Intensified eradication campaign begins• 1975. Last case in India• 1977. Last case in Somalia – last endemic case in the
world• 1978. Last case in the world – Birmingham, UK • 1980. Eradication certified by WHO• 1993. Genome of variola virus sequenced• ???? Last stocks of variola virus to be destroyed
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Sequestration of Variola VirusAfter Smallpox Eradication• WHO writes to all governments• WHO writes to all Virus laboratories• WHO scans index medicus for variola research
– Writes to directors
• WHO requests destruction or transfer of all stocks
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Sequestration of Variola VirusAfter Smallpox Eradication• In 1975, 75 laboratories held variola virus
stocks
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Year No of Laboratories
1975 75
1977 18
1978 13
1979 7
1980 6
1981 4
1982 3
1983 2
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Sequestration of Variola VirusAfter Smallpox Eradication• Forgotten stocks have been discovered on at
least 4 occasions
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Year No of Laboratories
1979 USA
1979 Tanzania
1985 UK
2014 USA
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Sequestration of Variola VirusAfter Smallpox Eradication• Centralised in 2 locations:
– CDC, Atlanta, USA– Vector, Novosobirsk, Russia
• Maximum security lab’s• Biennial inspection by WHO• All work with live variola virus requires prior
approval by WHO
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Why Retain Variola Virus AfterSmallpox Eradication?• Smallpox is a human disease *• Treatment requires anti-virals *
– Brincidofovir– Tecovirimat
• The vaccine has significant side-effects *– A safer vaccine is required
• Modern diagnostics
• * These rationales do not apply to rinderpest
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Emergence of Related Viruses
• Monkeypox– Human infection only apparent since 1970
• Clinically similar to smallpox• Virus closely related to variola• Controlled by smallpox vaccine
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Emergence of Related Viruses: The Human Niche
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Smallpox Vaccine Empty Monkeypox?
• Smallpox eradication opened an ecological niche
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Why is this important?
• Eradication – leads to loss of herd immunity– Vulnerability to deliberate or accidental release
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Summary• Identification of laboratories and stocks is
essential• Oversight of handling laboratories is essential
– Accidental releases have occurred– Birmingham 1978 – after last endemic case
• Emergence of related viruses– e.g. monkeypox
• Bioterrorism/accident– The virus could be recreated– All research with virus must be regulated
• Diagnostics/surveillance– Subject to changing technology– Need to define requirements
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Questions?
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Questions?
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