Spatial, temporal and spatio-temporal clusters of measles incidence at the county level in Guangxi, China during 2004-2014: flexibly shaped scan statistics.

BACKGROUND: Outbreaks of measles re-emerged in Guangxi province during 2013-2014, where measles again became a major public health concern. A better understanding of the patterns of measles cases would help in identifying high-risk areas and periods for optimizing preventive strategies, yet these patterns remain largely unknown. Thus, this study aimed to determine the patterns of measles clusters in space, time and space-time at the county level over the period 2004-2014 in Guangxi. METHODS: Annual data on measles cases and population sizes for each county were obtained from Guangxi CDC and Guangxi Bureau of Statistics, respectively. Epidemic curves and Kulldorff's temporal scan statistics were used to identify seasonal peaks and high-risk periods. Tango's flexible scan statistics were implemented to determine irregular spatial clusters. Spatio-temporal clusters in elliptical cylinder shapes were detected by Kulldorff's scan statistics. Population attributable risk percent (PAR%) of children aged ≤24 months was used to identify regions with a heavy burden of measles. RESULTS: Seasonal peaks occurred between April and June, and a temporal measles cluster was detected in 2014. Spatial clusters were identified in West, Southwest and North Central Guangxi. Three phases of spatio-temporal clusters with high relative risk were detected: Central Guangxi during 2004-2005, Midwest Guangxi in 2007, and West and Southwest Guangxi during 2013-2014. Regions with high PAR% were mainly clustered in West, Southwest, North and Central Guangxi. CONCLUSIONS: A temporal uptrend of measles incidence existed in Guangxi between 2010 and 2014, while downtrend during 2004-2009. The hotspots shifted from Central to West and Southwest Guangxi, regions overburdened with measles. Thus, intensifying surveillance of timeliness and completeness of routine vaccination and implementing supplementary immunization activities for measles should prioritized in these regions.

Timeliness and completeness of measles vaccination among children in rural areas of Guangxi, China: A stratified three-stage cluster survey.

BACKGROUND: Large-scale outbreaks of measles occurred in 2013 and 2014 in rural Guangxi, a region in Southwest China with high coverage for measles-containing vaccine (MCV). This study aimed to estimate the timely vaccination coverage, the timely-and-complete vaccination coverage, and the median delay period for MCV among children aged 18-54 months in rural Guangxi. METHODS: Based on quartiles of measles incidence during 2011-2013, a stratified three-stage cluster survey was conducted from June through August 2015. Using weighted estimation and finite population correction, vaccination coverage and 95% confidence intervals (CIs) were calculated. Weighted Kaplan-Meier analyses were used to estimate the median delay periods for the first (MCV1) and second (MCV2) doses of the vaccine. RESULTS: A total of 1216 children were surveyed. The timely vaccination coverage rate was 58.4% (95% CI, 54.9%-62.0%) for MCV1, and 76.9% (95% CI, 73.6%-80.0%) for MCV2. The timely-and-complete vaccination coverage rate was 47.4% (95% CI, 44.0%-51.0%). The median delay period was 32 (95% CI, 27-38) days for MCV1, and 159 (95% CI, 118-195) days for MCV2. CONCLUSIONS: The timeliness and completeness of measles vaccination was low, and the median delay period was long among children in rural Guangxi. Incorporating the timeliness and completeness into official routine vaccination coverage statistics may help appraise the coverage of vaccination in China.

Parental migration and children's timely measles vaccination in rural China: a cross-sectional study.

OBJECTIVE: With the rapid economic development in China, millions of rural residents are migrating to the cities to gain employment, resulting in numerous left-behind children (LBC). Simultaneously, outbreaks of measles continue to occur, yet the effect of parental migration on children's vaccination status is largely unknown. This study aimed to evaluate the association between parental migration and children's timely measles vaccination in rural China, after adjusting for family socio-economic status (SES) indicators. METHODS: We conducted a cross-sectional survey using multistage sampling among children aged 18-54 months in rural Guangxi of China. Information on measles vaccination status was obtained from the child's vaccination certificate, and data on SES were collected by interviewing the child's primary guardian. Family SES and vaccination coverage were compared between LBC and non-left-behind children (NLBC) using weighted logistic regression, while the delay in vaccination was compared using Kaplan-Meier survival analysis. RESULTS: Of the 1216 study children, 46% were LBC and 54% were NLBC. Compared to NLBC, the coverage of timely measles vaccination was significantly lower, and the median delay period was longer among LBC. After adjusting for SES indicators, LBC were significantly more likely to have an untimely vaccination for their first dose of measles vaccine than NLBC (OR = 1.33, 95% CI = 1.02-1.75). CONCLUSIONS: Due to the negative effect of parental migration and family SES, LBC were more likely to encounter serious delays of measles vaccination in rural China. Optimising vaccination policies could facilitate timely vaccination among LBC in rural China.

[Study on the spatiotemporal trend of Japanese encephalitis in Guangxi, based on geographic information system and space-time permutation scan statistic].

OBJECTIVE: To study the spatiotemporal trend of Japanese encephalitis in Guangxi Zhuang Autonomous Region between 1989 and 2006. METHODS: Retrospective space-time permutation scan statistic and inverse distance weighted (IDW) interpolation were employed to detect the spatiotemporal trend of Japanese encephalitis in Guangxi, from the year 1989 to 2006. RESULTS: The spatiotemporal pattern of Japanese encephalitis was divided into four phases by IDW interpolation maps, from 1989 to 2006. The first phase was spatiotemporal cluster located in southeast region, from 1989 to 1996. The second phase showed discrete distribution from 1997 to 1998. The third phase of spatiotemporal cluster located in Lingshan county, Pubei county and Bobai county, in 1999. And the last phase was spatiotemporal cluster located in northwest region from 2000 to 2006. Three statistically significant spatiotemporal clusters were detected by retrospective space-time permutation scan statistic. The primary cluster appeared in 1999 (LLR = 253.25, P = 0.001, RR = 4.62), with 109°54' E, 22°28' N (located in Pubei county) as its center and radiated 45.24 km. From 2000 to 2006, the secondary cluster showed in northwest (LLR = 75.91, P = 0.001, RR = 1.88), with center located at 105° 23' E, 24° 68' N (Longlin county), and radiated 199.85 km. From 1989 to 1996, the other secondary cluster appeared in the southeast area (LLR = 46.29, P = 0.001, RR = 1.16), with center located at 110°94' E, 24°03' N (Zhaoping county) and radiated 229.12 km. CONCLUSION: Space-time permutation scan statistic and geographical information system could be applied to quantitatively detect the potentially spatiotemporal trend of the disease. The spatiotemporal cluster shifted from southeast to northwest, from 1989 to 2006.