Via The Lancet Infectious Diseases, an editorial: Yellow fever: the consequences of neglect. Excerpt:
But shouldn't the Angolan outbreak have been contained because of the availability of a cheap and effective vaccine? That should have been the case but actually the progressive spread of yellow fever has been facilitated by long-standing issues in funding and implementing immunisation.
Despite mass vaccination campaigns, vaccination coverage for yellow fever in endemic countries remains well below the recommended 80% of the population. This suboptimal coverage implies that herd immunity is not reached, leaving sections of the population vulnerable to infection and consequently a potential source of spread of the disease to other areas.
The other crucial issue hampering the control of the current yellow fever outbreak has been the lack of vaccine doses. For years, the production of vaccine has been far below global demand. WHO stocks around 7 million doses of yellow fever vaccine for possible emergencies. Although all those doses have already been sent to Angola this year, full vaccination coverage has not been reached yet.
Since the Angolan population alone amounts to 24 million people, the number of cases is increasing in Kinshasa (DRC), and unlinked yellow fever cases have also been reported in other countries (Ghana and Uganda), vaccination of all people at risk is not possible at the moment. One way to increase the vaccination coverage in the coming months could be the use of a lower dose of vaccine (a fifth of the original dose).
Two clinical trials have shown that lower doses of the vaccine can still generate immunological protection against yellow fever in adults. However, WHO will evaluate this possible emergency measure towards the end of June, which could further delay the control of the yellow fever outbreak.
The seriousness of the outbreak was further highlighted on May 23, when in her address to the 69th World Health Assembly, WHO Director-General Margaret Chan remarked that WHO had been warning for a decade that changes in demography and land use patterns in Africa have created ideal conditions for explosive outbreaks of urban yellow fever. Chan also highlighted how suboptimal mosquito control in past years has been a key factor in the emergence of vector-borne diseases such as yellow fever.
WHO has called the yellow fever outbreak “a serious public health event”, but as the international spread of the disease has slowed and vaccine supplies are slowly recovering, they stopped short of declaring it a ‘public health emergency of international concern’, which would have given WHO additional powers to implement measures to contain the outbreak.
It is clear that the current yellow fever outbreak could have been more limited with better emergency planning and adequate vaccine production. While vaccine production restarts, we hope that African and Asian populations will not pay the price for the lack of preparation of the global health systems.