The stalemate continues over the question of when to destroy the last stocks of the virus that causes smallpox, a killer disease that was eradicated in 1980. One of the World Health Organization’s (WHO) two advisory committees on smallpox supports the stocks’ destruction, and the other opposes it. Last weekend, health ministers of the WHO’s 194 member states again postponed a decision and decided to set up a third WHO smallpox advisory committee in a bid to broker a consensus.

The issue came up again on the agenda of the annual meeting of the World Health Assembly, the WHO’s top decision-making body, which was held in Geneva, Switzerland, from 19 to 24 May. It was last discussed at the 2011 assembly, which reaffirmed that the stocks of the variola virus should be destroyed but deferred to this year’s meeting discussion on any date of destruction.

A central question remains whether research of public-health importance is still needed on the virus, or whether the last stocks should be destroyed to eliminate the threat of an accidental release from the two labs where they are held — at the US Centers for Disease Control and Prevention in Atlanta, Georgia, and the Russian State Research Center of Virology and Biotechnology in Koltsovo, near Novosibirsk.

The final agenda of this year’s meeting, however, asked ministers only to take note of a WHO update report to the assembly on progress on completing needed research. The WHO’s ‘advisory committee on variola virus research’ (ACVVR), which oversees and approves any research using the stocks, felt that live virus was no longer needed to develop diagnostics and vaccines, but was still needed to develop antiviral drugs. By contrast, its ‘advisory group of independent experts to review the smallpox research programme’ (AGIES) felt that there was no research justification for holding on to the stocks.

Although the ACVVR reached a consensus on antivirals, there was considerable debate about this among its members. Some argued, for example, that with two promising drugs — tecovirimat and brincidofovir — close to licensing, virus stocks were no longer needed. Others felt that the virus should be kept in case these drugs failed to get licensed, requiring the development of other compounds.

The AGIES considered the same issues but swung towards virus being no longer needed to develop antivirals — it also suggested that should a future need arise to develop new drugs, live virus could in any case be recreated from viral DNA. The ACVVR is often perceived as being more focused on research interests, and the AGIES on public-health aspects.

By the time the WHO assembly got to discussion of destruction of smallpox stocks, it was near the end of the last day of the meeting. It quickly became clear that there were sharply divided opinions and no consensus, according to Glenn Thomas, a WHO spokesman. The decision to setup a third expert group is intended to bring together a mix of scientists and public-health and other experts to review all the elements of the debate and take the issue forward, says Thomas.

For the moment, the precise terms of reference of the group, or its composition, have yet to be decided. The latter will be important, as the destruction of the variola stocks is also a political issue. The United State is strongly opposed to destruction of the virus stocks, largely because — like many other developed countries — it wants to pursue research that it believes might help to protect against a bioweapons attack by rogue states or terrorists, who may have access to undeclared stocks (see ‘WHO to decide fate of smallpox stocks‘).

Some scientists are also keen for smallpox research using live virus not to be stopped, but continued and expanded. Two members of the ACVVR, Clarissa Damaso, of the Federal University of Rio de Janeiro in Brazil, and Grant McFadden, of the University of Florida in Gainesville, have argued, for example, that the WHO’s restricting of smallpox research to tightly circumscribed public-health applications has limited fundamental research that could advance public health. In an opinion piece published 1 May in the journal PLoS Pathogens, along with Inger Damon, head of the poxvirus and rabies branch of the Centers for Disease Control and Prevention in Atlanta, Georgia, they argue that: “the research agenda with live variola virus is not yet finished and that significant gaps still remain”.

But the majority of the health ministers of the WHO member states — including those of many poorer countries, who view the risks of an accidental release as outweighing any research benefits — want the stocks of virus destroyed at some point. The question for the WHO assembly is, as always, when? But yet again, it has kicked that can down the road.