Interpreting the transmissibility of measles in two different post periods of supplementary immunization activities in Hubei China.

Tuesday, 24th of January 2017

Vaccine. 2017 Jan 19. pii: S0264-410X(17)30015-4. doi: 10.1016/j.vaccine.2017.01.010. [Epub ahead of print]

Interpreting the transmissibility of measles in two different post periods of supplementary immunization activities in Hubei China.

Chong KC¹ Zhang C² Zee BC¹ Luo T³ Wang L² Tam GC³ Jia KM³ Sun R¹ Wang MH⁴ Guan X⁵.

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Abstract

Although evidence has shown that supplementary immunization activity (SIA) campaigns greatly reduce the incidence of measles their effects on disease transmissibility have seldom been monitored. A great decrease in the number of cases may be a false signal of early success towards measles elimination to policy makers. By interpreting the transmissibility in two different post-SIA periods in Hubei China the current study showed sustained measles transmissions despite a reduced number of cases. Two population-based cross-sectional serological surveys of measles antibodies were conducted in Hubei province in mid-2010 and mid-2011 after the implementation of SIAs. Immunoglobulin G (IgG) antibodies against measles were measured by enzyme-linked immunosorbent assay (ELISA). Based on the estimated age-specific susceptibility levels the effective reproduction number (R) a key indicator of disease transmissibility was determined by the next generation matrix in transmission model. The results revealed an overall IgG seroprevalence of 88.0% (95% confidence interval [CI]: 85.6-90.4%) and 89.6% (95%CI: 88.0-91.2%) respectively in the two different periods. Comparatively lower seroprevalence rates were observed among children less than 24months of age and young adults 15 to 19years of age in 2011. The Rs were 0.76 and 1.53 for the two study periods. In conclusion even though the incidence was reduced to below 1/100000 in both 2010 and 2011 the reproduction number in 2011 indicates a high risk for sustained measles transmission. This finding was potentially due to a lower seropositivity rate among young adults that had not been covered in the first SIA. Thus implementation of SIA targeted to appropriate age groups is recommended. Regular monitoring of seroprevalence is also suggested to track disease transmissibility and to align SIA with the appropriate age groups.

Copyright © 2017. Published by Elsevier Ltd.