Key result
The oral polio vaccine campaign reduced the projected wild poliovirus attack rate in Bedouin children under 10 from 57% to 42% and likely shortened the outbreak duration by a mean of 309 days.
Why the study?
Does an OPV campaign reduce the attack rate and duration of a wild poliovirus outbreak in an IPV-vaccinated population of children?
Does an OPV campaign reduce the attack rate and duration of a wild poliovirus outbreak in an IPV-vaccinated population of children?
Absolute Risk Reduction: 15 (95% CI 0–40)
Absolute Event Rate: 42% vs 57%
Absolute Risk Reduction: 15%
An OPV campaign is essential for interrupting wild poliovirus transmission and reducing outbreak duration even in a developed country with high IPV coverage.
May support OPV campaigns during wild poliovirus outbreaks in high-IPV settings; leaves open prospective validation.
BACKGROUND: Polio eradication is an extraordinary globally coordinated health program in terms of its magnitude and reach, leading to the elimination of wild poliovirus (WPV) in most parts of the world. In 2013, a silent outbreak of WPV was detected in Israel, a country using an inactivated polio vaccine (IPV) exclusively since 2005. The outbreak was detected using environmental surveillance (ES) of sewage reservoirs. Stool surveys indicated the outbreak to be restricted mainly to children under the age of 10 in the Bedouin population of southern Israel. In order to curtail the outbreak, a nationwide vaccination campaign using oral polio vaccine (OPV) was conducted, targeting all children under 10. METHODS: A transmission model, fitted to the results of the stool surveys, with additional conditions set by the ES measurements, was used to evaluate the prevalence of WPV in Bedouin children and the effectiveness of the vaccination campaign. Employing the parameter estimates of the model fitting, the model was used to investigate the effect of alternative timings, coverages and dosages of the OPV campaign on the outcome of the outbreak. RESULTS: The mean estimate for the mean reproductive number was 1.77 (95 % credible interval, 1.46-2.30). With seasonal variation, the reproductive number maximum range was between zero and six. The mean estimate for the mean infectious periods was 16.8 (8.6-24.9) days. The modeling indicates the OPV campaign was effective in curtailing the outbreak. The mean estimate for the attack rate in Bedouin children under 10 at the end of 2014 was 42 % (22-65 %), whereas without the campaign the mean projected attack rate was 57 % (35-74 %). The campaign also likely shortened the duration of the outbreak by a mean estimate of 309 (2-846) days. A faster initiation of the OPV campaign could have reduced the incidence of WPV even if a lower coverage was reached, at the risk of prolonging the outbreak. CONCLUSIONS: OPV campaigns are essential for interrupting WPV transmission, even in a developed country setting with a high coverage of IPV. In this setting, establishing ES of WPV circulation is particularly crucial for early detection and containment of an outbreak.
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Yaari et al. (2016) studied Wild poliovirus (WPV1) transmission (n=57,882). Oral polio vaccine (OPV) campaign vs. No OPV campaign (projected) was evaluated on Attack rate at the end of 2014 (15% absolute reduction, 95% CI 0-40). The oral polio vaccine campaign reduced the projected wild poliovirus attack rate in Bedouin children under 10 from 57% to 42% and likely shortened the outbreak duration by a mean of 309 days.
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