WORLD HEALTH ORGANIZATION FIFTY-FIFTH WORLD HEALTH ASSEMBLY Provisional agenda item 13.16 A55/21 5 April 2002
Smallpox eradication: destruction of variola virus stocks Report by the Secretariat
1. In May 1999, the Fifty-second World Health Assembly by resolution WHA52.10 authorized temporary retention up to not later than 2002 of the existing stocks of Variola virus at the two current locations,1 for the purpose of further international research. It also requested the Director-General: (1) to appoint a new group of experts which will establish what research, if any, must be carried out in order to reach global consensus on the timing for the destruction of existing variola virus stocks, and will: (a) (b) advise WHO on all actions to be taken with respect to variola; develop a research plan for priority work on the variola virus;
(c) devise a mechanism for reporting of research results to the world health community; (d) outline an inspection schedule to confirm the strict containment of existing stocks and to assure a safe and secure research environment for work on the variola virus, and make recommendations on these points; (2) to facilitate the full participation in the work of the new group of experts of a limited number of scientists and public health experts from Member States of each of the WHO regions; (3) to report the initial recommendations and plans of the group of experts, including relevant costs for WHO, to the Executive Board at its 106th session in May 2000, providing that external funding has been made available for this purpose; (4) to present a detailed report, including progress of the research programme on the smallpox virus, to the Executive Board and Health Assembly as soon as possible, but in any event not later than 2002, and to make recommendations to the Executive Board and Health
Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America, and the Russian State Centre for Research on Virology and Biotechnology, Koltsovo, Novosibirsk Region, Russian Federation.
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Assembly regarding their proposals for the date of final destruction of the remaining stocks of variola virus. 2. The WHO Advisory Committee on Variola Virus Research, composed of 18 members from all WHO regions and advised by some 10 scientific academic experts from such areas as public health, fundamental applied research and regulatory agencies, was subsequently established and has met three times. Reports from the first two meetings have already been submitted to the Health Assembly.1 This document provides a report of the third meeting (Geneva, 3 and 4 December 2001).
THIRD MEETING OF THE WHO ADVISORY COMMITTEE ON VARIOLA VIRUS RESEARCH 3. The Committee agreed that, despite the considerable progress that had been made in investigating Variola virus, significant components of this research, most notably the refinement and use of an animal model developed in 2001 and the development of antiviral drugs, were unlikely to be completed by the end of 2002. Further, during extensive discussion about the potential availability of an animal model, additional research was identified that would necessitate access to live Variola virus stocks after the expected 2002 destruction date. 4. The Committee’s main recommendation, therefore, was that serious consideration should be given to further extending the deadline for the destruction of Variola virus in order to allow essential research to be completed. Further, this additional research with live virus should continue to be carefully monitored and reviewed under the auspices of WHO, and steps should be taken to ensure that all approved research would remain outcome-focused and time-limited and periodically reviewed. 5. Review of Variola virus strains in the two repositories. It was previously noted that the Centers for Disease Control and Prevention held 451 viral isolates obtained from different continents and countries when smallpox was endemic.2 The current review and the studies reported at the meeting concentrated on some 50 isolates in the Russian collection that were not present in the American collection. From these isolates, 23 strains from scab material and previously lyophilized samples were viable in tissue-culture. Isolation of DNA from these strains is continuing; already, two genomes have been completely cloned and at least five others will be cloned by the end of 2002. The Committee agreed that before the end of 2002 further consideration should be given to the necessity of holding the wide range of isolates currently available in the two repositories. 6. Nucleic acid-based diagnostics. Several methods have been devised recently for very sensitive detection of Variola virus DNA and to distinguish this DNA from that of other orthopoxviruses, the most promising being analysis by polymerase chain reaction (PCR) of restriction fragment length polymorphisms, multiplex PCR and real-time PCR with fluorigenic probes. Some of these tests have been used in the definitive diagnosis of a recent laboratory-acquired infection with a non-variola orthopoxvirus. 7. The results obtained indicate that single-gene restriction fragment length polymorphisms and multiplex PCR detection methods are useful for detecting Variola virus in clinical samples. The Committee noted that, although the real-time PCR test has greater sensitivity and can therefore detect 1 2
Documents A53/27 and A54/16. Document A54/16.
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infection at an earlier stage, it requires the use of expensive equipment and, so far, cannot consistently distinguish between species of orthopoxviruses. An extended PCR test for restriction fragment length polymorphisms has proved useful in defining the origin of an isolate, but may require prior tissueculture passage of clinical samples. 8. The Committee recognized the significant progress made in the area of molecular diagnosis but agreed that there was still scope for improving the sensitivity of the tests available. For example, it would be useful to know how early infection with Variola virus might be detected at the prodromal stage. An ultimate goal might be the development of relatively cheap hand-held equipment for the detection of Variola virus DNA and diagnosis of infection. 9. To further this important area of work, the Committee encouraged investigators to share diagnostic reagents, essential primer sequences for PCR assays and protocols where appropriate. This cooperation would be particularly useful for enhancing capabilities in different countries for the rapid and reliable detection and diagnosis of Variola virus infections. 10. Sequence analysis of Variola virus DNA. The Committee was informed that the complete genomes of an additional seven isolates of Variola virus had been sequenced, bringing the total number of full-length genome sequences to 10 (nine variola major and one variola minor strain). The sequences were highly conserved. To counter the criticism that this result was a consequence of tissueculture passage, the Committee suggested that further thought be given to sequencing DNA directly from scab material. 11. The Committee noted that a considerable amount of information on the nucleic acid sequences of variola viruses was now available. After discussion, it was agreed that further sequencing of the more variable genomic termini had priority over the derivation of sequences of additional whole genomes. This would be useful for forensic purposes if there were ever a deliberate release of variola viruses, and reference DNA should be kept for this purpose. 12. Serological assays. Polyclonal and monoclonal antibodies against Vaccinia virus have been used in various enzyme-linked immunosorbent assays to evaluate their usefulness in the detection of Variola virus antigens. Polyclonal antibodies detected all viral strains more readily than the monoclonal antibodies currently available, but, although the methods appear to be relatively sensitive, they do not facilitate the detection of all viral isolates. The Committee concluded that a Variola virusspecific serological assay could usefully complement molecular diagnostic techniques, particularly as a second method to detect infection. However, further validation of the tests available was needed. 13. Animal models. The Committee was informed of the successful infection of cynomolgus monkeys with two different Variola virus strains by intravenous, or intravenous plus aerosol, routes. The disease induced shared several pathological features with human smallpox. However, in the particular experiment, the dose of virus was very high and the course of the disease was much faster. 14. Additional studies are needed to improve and validate this animal model, but this would need work extending beyond 2002. The monkey model has the potential to be used as an assay in prophylactic or therapeutic studies with live Variola virus and could also provide access to good diagnostic reagents. Other surrogate animal models are being investigated in parallel, in particular the infection of monkeys with Monkeypox virus and the infection of rodents with Cowpox virus, in order to obtain data that relate more to models using Variola virus.
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15. Drug development. Most studies have focused so far on the efficacy of cidofovir against poxviruses. This compound has demonstrable activity against cowpox in mice and against monkeypox in monkeys. In the United States of America cidofovir may be used in emergencies as an investigational new drug to treat significant adverse events following immunization with the current smallpox vaccine, and in the unlikely event of smallpox re-emerging. 16. In vitro screening of other chemical entities has identified more than 140 additional compounds with antiviral activity against poxviruses. The finding that some of these compounds have selective activity, inhibiting one or more orthopoxvirus but not necessarily Variola virus, supports the premise that access to live Variola virus is necessary for the effective screening of additional lead compounds. Most active compounds identified so far target the viral DNA polymerase and it was considered important to identify other viral gene products susceptible to drug intervention. 17. Vaccine development. The Committee agreed that the best safeguard against smallpox was vaccination. This strategy had been successfully deployed during the eradication programme, but the smallpox vaccine currently available was associated with a significant number of adverse events. This suggested that, although the current vaccine had proved its efficacy and utility, improvements were needed, particularly to facilitate the safe and effective immunization of vulnerable sectors of certain populations (the immunocompromised, the elderly, pregnant women and children with eczema). 18. The Committee therefore encouraged the delineation of further research into vaccine strategies that might use more attenuated Vaccinia virus strains, subunit vaccines or other promising approaches, including DNA vaccines. Results reported at the meeting and in numerous publications on attenuated Vaccinia virus recombinants encoding antigens from other pathogens indicate the potential value of these alternative strategies for vaccine development. It was recognized that access to live Variola virus would be necessary to assess the efficacy of new, improved smallpox vaccines and, ultimately, to obtain regulatory approval. 19. Conclusions and recommendations. The Committee acknowledged that important progress has been made in health-oriented research involving Variola virus. However, it concluded that much essential research will not be completed by the end of 2002. The Committee recommended that further goal-oriented research, extending beyond the expected 2002 destruction deadline, could be justified so that the world population could be adequately prepared for the unlikely, but potentially catastrophic, event of a re-emergence of smallpox. 20. It was further recommended that the current advisory committee should continue its role in monitoring and reviewing all research involving live Variola virus, and that steps should be taken to ensure that all approved research would remain outcome-focused and time-limited.
SMALLPOX VACCINE INVENTORIES 21. Preparedness for smallpox outbreaks. The recent deliberate use of Bacillus anthracis with the intent to harm a civilian population has raised public health concerns of Member States about potential exposure to intentionally released Variola virus and other biological agents. Efforts by WHO to support Member States, either in the event of intentional use of Variola virus as a biological weapon or of the emergence of another orthopoxvirus disease, include activities to strengthen preparedness through monitoring and investigation of rumours about cases of smallpox; ensuring the availability of diagnostic capacity for orthopoxviruses; compilation of global inventories of vaccine stocks and vaccine manufacturers; ensuring access to training material and expertise; establishing standard
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operating procedures, tools and a roster of experts for field response to and investigation of outbreaks. New guidance and results of the inventories will be provided, as they become available, to Member States. 22. Monitoring and investigation of rumours of smallpox. Between 1 January 2000 and 14 March 2002, rumours of suspected smallpox cases were reported on eight occasions from five different WHO regions. All the events were investigated through the Global Outbreak Alert and Response Network. In one instance there had been accidental exposure to Vaccinia virus, leading to the admission to hospital of eight children. Two events were associated with varicella outbreaks, one with a measles outbreak, and four were of unknown etiology. 23. Twenty-two outbreaks of suspected monkeypox, all but one in the Democratic Republic of the Congo, were reported to WHO during the same period. As a result of the investigations, 11 were laboratory-confirmed as monkeypox, and four were shown to be varicella. Laboratory results are pending for five outbreaks. On two occasions, laboratory investigation was not possible. 24. Inventory of national stocks of smallpox vaccine. A survey was conducted in order to assess the availability of stocks of vaccine and number of doses, the availability of vaccine-manufacturing facilities, and the existence of plans to produce or to procure the vaccine from a source other than a national manufacturer. Accordingly, on 26 October 2001, all 191 Member States were approached through their permanent missions to the United Nations and/or through WHO regional offices and asked to complete a questionnaire. 25. As of 14 March 2002, 91 (48%) Member States had responded to the survey. Thirteen respondents (14%) reported holding stocks of smallpox vaccine and 25 (27%) reported the presence of production facilities capable of manufacturing vaccine on the national territory, with 19 (21%) planning to produce or already producing vaccine. In 40 (44%) countries, authorities expressed their intention to procure vaccine elsewhere or had already done so; most of these countries specified that they would purchase the vaccine only in response to a real threat or a recommendation to do so from WHO. 26. Inventory of smallpox vaccine manufacturers. Altogether 63 potential smallpox vaccine manufacturers were contacted during the period 10 November 2001 to 6 March 2002, and information about availability of stocks of vaccine, their quantity and characteristics (year of production, Vaccinia virus seed strain used and potency), plans to produce and intention to make the vaccine commercially available was collected by means of a self-administered questionnaire. Replies were received from 33 of the 63 manufacturers (52%). Of these, nine (27%) reported having stockpiles of vaccine that was produced between 1972 and 1980 and was derived from a variety of seed strains. Seven indicated that vaccine potency had been tested between 1999 and 2002. Of 10 manufacturers that were considering production, six indicated that they could make the vaccine available on the market as early as April 2002, with production levels up to 500 million doses per year. 27. Worldwide availability of smallpox vaccine. According to information gathered through the surveys of Member States and vaccine manufacturers about 110 million doses of smallpox vaccine are estimated to be currently available worldwide, including a stock of 500 000 doses held by WHO in Geneva. This figure is a conservative estimate, as some respondents were uncertain about the number of doses they held: this number varied within a range of several million doses. Several Member States and manufacturers in those countries did not respond to the surveys. Additionally, some respondents declined to disclose information about vaccine stocks held in their country. Furthermore, the potency of these doses is not known in all cases.
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28. Preliminary results of ongoing trials to test the efficacy of diluted vaccine are promising and might allow existing stockpiles to be expanded up to fivefold.
RECOMMENDATIONS OF THE DIRECTOR-GENERAL 29. Having noted the report of the Advisory Committee for Variola Virus Research, including the recommendations for research priorities, and its conclusion that the research programme will not be completed by the end of 2002, the Director-General recommends that: • the WHO Advisory Committee on Variola Virus Research should continue to oversee the Variola virus research programme and that the research programme should be conducted in an open and transparent manner; • the research programme should be completed as quickly as possible, and a proposed new date for destruction should be set when the research accomplishments and outcomes allows consensus to be reached on the timing of destruction of Variola virus stocks; • regular biosafety inspections of the storage and research facilities should be continued in order to confirm the strict containment of existing stocks and to ensure a safe research environment for work with Variola virus; • depending on progress, a report on the research should be submitted to the Executive Board and Health Assembly in two to three years’ time. 30. The Executive Board at its 109th session endorsed these recommendations.
ACTION BY THE HEALTH ASSEMBLY 31. The Health Assembly is invited to consider the adoption of the following resolution. The Fifty-fifth World Health Assembly, Recalling resolutionWHA52.10 on smallpox eradication; Having considered the report on Smallpox eradication: destruction of variola virus stocks;1 Noting that the research programme will not be completed by the end of 2002, 1. DECIDES to authorize the further, temporary, retention of the existing stocks of live Variola virus at the current locations specified in resolution WHA52.10, for the purpose of enabling further international research, on the understanding that the research should be completed as quickly as possible and a proposed new date for destruction should be set when the research accomplishments and outcomes allows consensus to be reached on the timing of destruction of Variola virus stocks; 1
Document A55/21.
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2.
REQUESTS the Director-General: (1) to continue the work of the Advisory Committee on Variola Virus Research with respect to the research involving Variola virus stocks and to ensure that the research programme is conducted in an open and transparent manner; (2) to ensure that regular biosafety inspection of the storage and research facilities is continued in order to confirm the strict containment of existing stocks and to ensure a safe research environment for work with Variola virus; (3) depending on progress achieved in the research programme, to report at the latest to the Fifty-eighth World Health Assembly, through the Executive Board.
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