BackgroundMeasles outbreaks have occurred in some countries despite supplementary immunization activities (SIA) using measles-containing vaccine with high vaccination coverage. We conducted a cross-sectional seroprevalence survey to estimate population immunity in Lao People's Democratic Republic where repeated mass immunization has failed to eliminate measles.Methods and findingsIn this nationwide multistage cluster sampling survey conducted in 2014 based on probability proportionate to size sampling, blood samples were collected from 2,135 children and adults living in 52 randomly selected villages. Anti-measles and anti-rubella IgG were measured, and IgG prevalence was calculated. We applied mathematical modelling to estimate the number of cases of congenital rubella syndrome (CRS) in 2013 that were averted by the 2011 SIA. A stability testing was applied to the MR vaccine at 4°C, 25°C, and 35°C to examine stability differences between measles and rubella vaccine components. Measles IgG prevalence was significantly lower in the target age groups (5–21 years) of the 2011 SIA using a combination vaccine for measles and rubella vaccine (MR vaccine) than in young adults (22–39 years) (86.8% [95% CI: 83.0–90.6] vs. 99.0% [98.3–99.8]; p<0.001), whereas rubella IgG prevalence was significantly higher (88.2% [84.5–91.8] vs. 74.6% [70.7–78.5]; p<0.001). In the SIA target age groups, prevalence of measles IgG, but not rubella IgG, increased with age. CRS cases prevented in 2013 ranged from 16 [0–50] to 92 [32–180] if the force of infection had remained unchanged or had been reduced by 75%, respectively. In freeze-dried conditions, the measles vaccine component was more heat sensitive than the rubella component.ConclusionsInconsistent IgG prevalence between measles and rubella in Lao PDR can be partly explained by different stability of the measles and rubella vaccine components under heat exposure. Suboptimal vaccine handling may cause insufficient immunogenicity for measles, which subsequently leads to an outbreak despite high SIA coverage, while direct evidence is lacking. Temperature monitoring of the vaccine should be conducted.

BackgroundHepatitis B is regarded as a serious public health issue in Lao People's Democratic Republic (Lao PDR), a Southeast Asian country. However, disease epidemiology among the general population is not well known, and thus a nationwide cross-sectional survey for hepatitis B surface antigen (HBsAg) prevalence in children and their mothers was conducted.Methods and findingsWe applied three-stage cluster sampling using probability proportionate to size. After randomly selecting child (5 to 9 years old) and mother (15 to 45 years old) pairs from the selected villages, questionnaires and HBsAg rapid tests were conducted. Data from 965 child and mother pairs were analyzed. Multivariate logistic regression analyses were used to investigate the independent association of individual background characteristics for the odds of being HBsAg positive. In total, 17 children and 27 mothers were HBsAg positive. HBsAg prevalence was estimated to be 1.7% (95% confidence interval: 0.8%-2.6%) in children, and 2.9% (95% confidence interval: 1.7%–4.2%) in their mothers after taking sampling design and weight of each sample into account. Mother's infection status was positively associated with HBsAg positivity in children (p<0.001), whereas other potential risk factors, such as ethnicity, proximity to health centers, and history of surgery, were not. There were no significant associations between mother's HBsAg status and history of surgery, and other sociodemographic factors.ConclusionsDespite the slow implementation of the hepatitis B vaccination program, HBsAg prevalence among children and their mothers was not high in Lao PDR compared to reports from neighboring countries. The reasons for the differences in prevalence among these countries are unclear. We recommend that prevalence surveys be conducted in populations born before and after the implementation of a hepatitis B vaccination program to better understand the epidemiology of hepatitis B.

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ObjectiveAll childhood vaccines, except the oral polio vaccine, should be kept at 2–8 °C, since the vaccine potency can be damaged by heat or freezing temperature. A temperature monitoring study conducted in 2008–2009 reported challenges in cold chain management from the provincial level downwards. The present cross-sectional pilot study aimed to assess the current status of the cold chain in two provinces (Saravan and Xayabouly) of Lao People’s Democratic Republic between March–April 2016. Two types of temperature data loggers recorded the temperatures and the proportions of time exposed to < 0 or > 8 °C were calculated.ResultsThe temperature remained within the appropriate range in the central and provincial storages. However, the vaccines were frequently exposed to > 8 °C in Saravan and < 0 °C in Xayabouly in the district storage. Vaccines were exposed to > 8 °C during the transportation in Saravan and to both > 8 and < 0 °C in Xayabouly. Thus, challenges in managing the cold chain in the district storage and during transportation remain, despite improvements at the provincial storage. A detailed up-to-date nationwide analysis of the current situation of the cold chain is warranted to identify the most appropriate intervention to tackle the remaining challenges.

Cancers including cervical cancer are leading causes of mortality in Lao PDR. Human papillomavirus (HPV) vaccination has been introduced as a pilot project. As a part the evaluation, program cost of the school-based vaccination was estimated. We employed an ingredient-based/ bottom-up costing study of incremental vaccine delivery cost using the WHO Cervical Cancer Prevention and Control Costing Tool (C4P). Both financial and economic costs are measured from the Ministry of Health perspective covering central supply unit to service provider levels. Costs are composed of labor cost and material cost but costs of building, vehicle and cold chain equipment are not included, except for extra cold chain equipment. Costs are presented in nominal value for the year 2013 (USD 1=7,855 LAK) in terms of total cost, cost component and unit cost. Scenarios for both 3-and 2-dose vaccination were explored. In two pilot provinces, there are 22 districts, 107 health centers, 917 schools and 13,558 target girls. We found that, with 100% coverage, the total costs of the 3-dose program were USD 106,677 and USD 135,479 for financial and economic cost, respectively. In terms of cost proportion by type of activities, service delivery comprised the highest percentage of economic cost (41.7%). For financial cost, supervision/AEFI comprised 42.5% and was the largest component. Costs per vaccination dose were USD 2.62 and USD 3.33 for financial and economic perspectives, respectively. Costs per fully immunized girl (FIG) for financial and economic perspective were USD 7.87 and USD 9.99, respectively. For a 2-dose vaccination scenario, costs per FIG were USD 5.7 and USD 7.9 for financial and economic cost, respectively. In conclusion, the overall cost of HPV vaccination program of Lao PDR was found to be in range of other countries, particularly those with similar features. Using a 2-dose vaccination schedule instead of a 3-dose schedule could save approximately one-third of the recurrent cost.