Vaccine-derived poliovirus in Nigeria

January 01, 0001

Vaccine-derived poliovirus in Nigeria

The largest recorded outbreak of a circulating vaccine-derived poliovirus (cVDPV), detected in Nigeria, provides a unique opportunity to analyze the pathogenicity of the virus, the clinical severity of the disease, and the effectiveness of control measures for cVDPVs as compared with wild- type poliovirus (WPV). These UK investigators identified cases of acute flaccid paralysis associated with fecal excretion of type 2 cVDPV, type 1 WPV, or type 3 WPV reported in Nigeria through routine surveillance from January 2005 through June 2009. The clinical characteristics of these cases, the clinical attack rates for each virus, and the effectiveness of oral polio vaccines in preventing paralysis from each virus were compared.

They found: "No significant differences were found in the clinical severity of paralysis among the 278 cases of type 2 cVDPV, the 2323 cases of type 1 WPV, and the 1059 cases of type 3 WPV. The estimated average annual clinical attack rates of type 1 WPV, type 2 cVDPV, and type 3 WPV per 100,000 susceptible children under 5 years of age were 6.8, 2.7, and 4.0, respectively. The estimated effectiveness of trivalent oral polio vaccine against paralysis from type 2 cVDPV was 38% per dose, which was substantially higher than that against paralysis from type 1 WPV (13%), or type 3 WPV (20%). The more frequent use of serotype 1 and serotype 3 monovalent oral polio vaccines has resulted in improvements in vaccine-induced population immunity against these serotypes and in declines in immunity to type 2 cVDPV."

The authors concluded: "The attack rate and severity of disease associated with the recent cVDPV identified in Nigeria are similar to those associated with WPV. International planning for the management of the risk of WPV, both before and after eradication, must include scenarios in which equally virulent and pathogenic cVDPVs could emerge."

We haven’t quite conquered polio yet.

For the full abstract, click here.

N Engl J Med 362(24):2360-2369, 24 June 2010
© 2010 to the Massachusetts Medical Society
Implications of a Circulating Vaccine-Derived Poliovirus in Nigeria. Helen E. Jenkins, R. Bruce Aylward, Alex Gasasira, et al. Correspondence to Dr. Jenkins: [email protected]

Category: B. Blood/Blood Forming Organs/Immune Mechanisms. Keywords: polio, vaccine-derived poliovirus, Nigeria, descriptive epidemiological study, journal watch.
Synopsis edited by Dr Linda French, Toledo, Ohio. Posted on Global Family Doctor 6 July 2010

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