Human response to live plague vaccine EV, Almaty region, Kazakhstan, 2014-2015

Abstract

Background In Kazakhstan, a live plague vaccine EV 76 NIIEG has been used for plague prophylaxis since the mid-1930s. Vaccination is administered yearly among people living in plague-enzootic areas. Similar practices are used in other former Soviet Union countries. Yet, to this day, the effectiveness period of the vaccine is unknown. It is also not clear how different factors can affect the effectiveness of the vaccine over time. Methods We surveyed changes in antibody levels specific for F1 antigens of Yersinia pestis among vaccinated people 4, 8, and 12 months post- vaccination. Blood samples were taken from the participants of the study for producing sera, which was later analyzed using indirect hemagglutination reaction with antigenic erythrocyte assay (micromethod) for identifying antibodies to F1 Y . pestis . Results In first-time-receivers of the plague vaccine, antibody titer reached the highest level of antibody that represents a conditionally protective titer after 4 months, dropped drastically after 8 months, and dropped again after 12 months. Similar results were obtained among those who have been vaccinated previously. However, in that group, the percentage of people with a level of antibody that represents a conditionally protective titer remained statistically significant even after 8 and 12 months. Conclusion Based on the results of this study, we recommend initiating vaccination campaigns for the medical and veterinary staff, as well as the general population four months prior to the springtime epizootics of plague among wild rodents.

Information support for monitoring post-vaccination immunity against plague

“…Зависимость динамики сероконверсии от крат ности предыдущих вакцинаций против чумы, установленная в результате изучения показа телей антительного ответа, согласуется с опу бликованными результатами многофакторного анализа, согласно которым частота вакцинации является статистически значимым фактором, вли яющим на уровень антител к белку F1 Y. pestis [13]. Так как прямая зависимость между серопозитив ностью и защитой от чумы отсутствует, существует потребность в исследовании коррелятивной связи между ключевыми показателями иммунологиче ской перестройки в динамике, когда множество параметров клеточных и гуморальных иммунных…”

Two fatal cases of plague after consumption of raw marmot organs

“…Y. pestis infection occurred even though the man had received an EV76 vaccine one year previously. There is no evidence showing that the available Y. pestis vaccines provide humans with long-lasting immunity and protection from plague [8,9].…”

The Analysis of Factors Influencing Immunologic Reactivity in People Vaccinated with a Live Plague Vaccine

“…кратности предыдущих вакцинаций против чумы. Эти данные согласуются с опубликованными результатами многофакторного анализа, согласно которым именно частота вакцинации является статистически значимым фактором, влияющим на уровень антител к F1 Y. pestis [11]. Влияние дополнительных факторов на показатели клеточного иммунного ответа было отмечено в ряде публикаций [12,13].…”