Epidemiological characteristics of Japanese encephalitis in Guizhou Province, China, 1971-2009.

OBJECTIVE: The aim of the study was to establish the contemporary epidemiological characteristics of Japanese encephalitis (JE) in Guizhou Province. METHODS: A retrospective study of National Notifiable Disease Reporting System (NNDRS) data from 1971 through 2009, was conducted to ascertain the geographical, seasonal, and age distributions of JE incidence in Guizhou Province, China. RESULTS: A total of 68 425 JE cases were reported in Guizhou from 1971-2009. The JE cases occurred sporadically in all 9 prefectures of Guizhou, mostly among residents of rural areas. Seasonal distribution of JE remained consistent over the period from 1971-2009 with the main transmission season starting from June to September and peaking in August. JE occurred mainly in children under the age of 15 years with peak incidence in the 0-6-year age group. Pearson's correlation analysis showed that JE vaccine distribution had a negative correlation with JE incidence rates during 1971-2009 (coefficient of correlation=-0.475, P<0.01). CONCLUSION: Over the period of 1971-2009, the JE incidence rate had declined dramatically in terms of geographical and age distributions due to JE vaccination to children at risk.

[Analysis of indexes used to evaluate immunization coverage rate of first dose of measles containing vaccine].

OBJECTIVE: To obtain an objective index of evaluating the immunization coverage rate of first dose of measles containing vaccine (MCV1)by comparison of the indexes in Guizhou Province. METHODS: Multistage random sampling method was applied to draw subjects from healthy children who had no measles history and aged from 8 months to 6 years of age. The investigated immunization coverage rate (IIR) and the estimated immunization coverage rate (EIR) were evaluated according to the positive rate of measles antibody as a gold standard, and the data of incidence cases as a reference. RESULTS: The IIR was 86.0% for the group aged from 8 months to 1 year, 90.1% for the group aged from 2 to 3 years and 90.2% for the group aged from 4 to 6 years. The adjusted estimated immunization coverage rate (AIIR) was 89.8%, 94.8% and 95.3%, respectively. Given the vaccine efficacy (VE) was 82.9%, the EIR1 was 59.8%, 71.6% and 77.9%, respectively and the AEIR1 was 68.2%, 79.7% and 86.8%, respectively; given the VE was 95%, the EIR1 was 84.3%, 90.1% and 92.7%, respectively, and the AEIR1 was 88.6%, 93.4% and 96.0%, respectively. The EIR2 was 97.9%, 94.5% and 91.4%, respectively. The relative difference was from 0 to 2.4% when compared with the estimated positive rate of AIIR and AEIR1 given the VE was 95% with the actual positive rate of measles antibody, the difference had no statistical significance(P>0.05). The relative error was low for the estimate positive rates of AIIR and EIR2 and AEIR1 (given the VE was 95%) for the children that had not suffered from measles, the relative error varied from 7.0% to 15.8%. CONCLUSION: The investigated immunization coverage rate after adjustment and the AEIR1 (VE 95%) were in line with the actual positive rate of measles antibody, which suggests that we should set an integral evaluation system for the immunization coverage rate based on AIIR and AEIR1.