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PLoS One. 2018 Mar 29;13(3):e0194931. doi: 10.1371/journal.pone.0194931. eCollection 2018.
Evaluation of nationwide supplementary immunization in Lao Peoples Democratic Republic: Population-based sero-prevalence survey of anti-measles and anti-rubella IgG in children and adults mathematical modelling and a stability testing of the vaccine.
Hachiya M1 Miyano S1 Mori Y2 Vynnycky E345 Keungsaneth P6 Vongphrachanh P7 Xeuatvongsa A8 Sisouk T7 Som-Oulay V7 Khamphaphongphane B7 Sengkeopaseuth B7 Pathammavong C8 Phounphenghak K8 Kitamura T1 Takeda M2 Komase K2.
Abstract
BACKGROUND:
Measles outbreaks have occurred in some countries despite supplementary immunization activities (SIA) using measles-containing vaccine with high vaccination coverage. We conducted a cross-sectional sero-prevalence survey to estimate population immunity in Lao Peoples Democratic Republic where repeated mass immunization has failed to eliminate measles.
METHODS AND FINDINGS:
In this nationwide multistage cluster sampling survey conducted in 2014 based on probability proportionate to size sampling blood samples were collected from 2135 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 rubellacomponent.
CONCLUSIONS:
Inconsistent 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.
PMID:
29596472
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