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Resurgence of mumps in Korea.

Park SH - Infect Chemother (2015)

Bottom Line: The recent resurgence of mumps is caused by multiple factors: suboptimal effectiveness of the current mumps vaccines, use of the Rubini strain vaccine, waning immunity in the absence of natural boosting due to the marked reduction in the mumps incidence, genotype mismatch between the vaccine and circulating mumps virus strains, and environmental conditions that foster intense exposures.Despite the suboptimal vaccine effectiveness in outbreak settings, maintaining the high vaccine coverage is an important strategy to prevent mumps outbreaks, given that the routine use of mumps vaccines has substantially reduced the incidence of mumps and its complications as compared with that in the pre-vaccine era.Furthermore, more effective mumps vaccines need to be developed in the future.

View Article: PubMed Central - PubMed

Affiliation: Division of Infectious Diseases, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.

ABSTRACT
Routine vaccination against mumps has markedly reduced its incidence. However, the incidence of mumps continuously has increased since 2007. In 2013, a large mumps epidemic occurred in Korea, and this epidemic is still an ongoing problem. This epidemic occurred primarily in school settings and affected vaccinated adolescents, predominantly male students. The recent resurgence of mumps is caused by multiple factors: suboptimal effectiveness of the current mumps vaccines, use of the Rubini strain vaccine, waning immunity in the absence of natural boosting due to the marked reduction in the mumps incidence, genotype mismatch between the vaccine and circulating mumps virus strains, and environmental conditions that foster intense exposures. Containment of mumps outbreaks is challenging because the sensitivity of diagnostic tests is low among vaccinees and control measures are less efficient because of the inherent nature of the mumps virus. Despite the suboptimal vaccine effectiveness in outbreak settings, maintaining the high vaccine coverage is an important strategy to prevent mumps outbreaks, given that the routine use of mumps vaccines has substantially reduced the incidence of mumps and its complications as compared with that in the pre-vaccine era. In order to control the current mumps epidemic and prevent further outbreaks, we need to better understand the dynamics of mumps among vaccinated populations and the changing epidemiology in Korea. Concerted efforts should be made to systematically monitor the immunization status of the Korean population and to improve diagnosis efficiency. Furthermore, more effective mumps vaccines need to be developed in the future.

No MeSH data available.


Related in: MedlinePlus

Changes in proportions of reported mumps cases in Korea by age between 2001 and 2014.
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Figure 3: Changes in proportions of reported mumps cases in Korea by age between 2001 and 2014.

Mentions: Demographically, mumps outbreaks occurred predominantly among middle and high school students aged 13-18 years, with the highest incidence among adolescents aged 15-17 year old. In this population, two-dose vaccine coverage was reported to reach approximately 99% [21]. The age range of affected individuals has become wider than in previous years, and the number of mumps cases appeared to increase in early teens (12-14 year olds) (Fig. 2). However, the proportion of mumps cases in this age group has not changed significantly during the past decade, whereas the proportion of older teens aged 15-19 years increased and that of children aged less than10 years decreased (Fig. 3.). Interestingly, the number of mumps cases also increased in those aged 30 years or older (Fig. 3), which suggests possible transmission of mumps virus to susceptible adults through household contacts [4]. The male predominance is also a distinct characteristic (the male to female ratio is 2.1). In addition, the age-specific gender ratio was more prominent among adolescents (3.78 among 15-19 year-olds) compared with other age groups (1.4 among 5-9 year-olds; 1.3 among 20-24 year-olds) (Fig. 2B) [20]. Geographically, there was a nationwide increase in the mumps incidence. As of 2008, the largest number of mumps cases was reported in Gyeonggi-do, which is densely populated with the population under the age of 20 years being highest. In 2014, a sudden surge in the number of mumps cases was observed in Gwangju and Jeollabuk-do (Fig. 4). Considering the overall population size of each region, the incidence rate over 100,000 population was particularly high in Daejeon (112.51/100,000) and Jeju-do (116.69/100,000) in 2013 and in Gwangju (218.35/100,000) and Jeollabuk-do (244.03/100,000) in 2014 [20]. The mumps incidence showed strong seasonality, with two peaks in spring (from May to June) and late autumn/early winter (from November to December), which coincided with the Korean school terms (Fig. 5). Despite the increased incidence of mumps, disease severity was low and complications were less frequent compared with the cause that occurred two decades ago [22].


Resurgence of mumps in Korea.

Park SH - Infect Chemother (2015)

Changes in proportions of reported mumps cases in Korea by age between 2001 and 2014.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4384450&req=5

Figure 3: Changes in proportions of reported mumps cases in Korea by age between 2001 and 2014.
Mentions: Demographically, mumps outbreaks occurred predominantly among middle and high school students aged 13-18 years, with the highest incidence among adolescents aged 15-17 year old. In this population, two-dose vaccine coverage was reported to reach approximately 99% [21]. The age range of affected individuals has become wider than in previous years, and the number of mumps cases appeared to increase in early teens (12-14 year olds) (Fig. 2). However, the proportion of mumps cases in this age group has not changed significantly during the past decade, whereas the proportion of older teens aged 15-19 years increased and that of children aged less than10 years decreased (Fig. 3.). Interestingly, the number of mumps cases also increased in those aged 30 years or older (Fig. 3), which suggests possible transmission of mumps virus to susceptible adults through household contacts [4]. The male predominance is also a distinct characteristic (the male to female ratio is 2.1). In addition, the age-specific gender ratio was more prominent among adolescents (3.78 among 15-19 year-olds) compared with other age groups (1.4 among 5-9 year-olds; 1.3 among 20-24 year-olds) (Fig. 2B) [20]. Geographically, there was a nationwide increase in the mumps incidence. As of 2008, the largest number of mumps cases was reported in Gyeonggi-do, which is densely populated with the population under the age of 20 years being highest. In 2014, a sudden surge in the number of mumps cases was observed in Gwangju and Jeollabuk-do (Fig. 4). Considering the overall population size of each region, the incidence rate over 100,000 population was particularly high in Daejeon (112.51/100,000) and Jeju-do (116.69/100,000) in 2013 and in Gwangju (218.35/100,000) and Jeollabuk-do (244.03/100,000) in 2014 [20]. The mumps incidence showed strong seasonality, with two peaks in spring (from May to June) and late autumn/early winter (from November to December), which coincided with the Korean school terms (Fig. 5). Despite the increased incidence of mumps, disease severity was low and complications were less frequent compared with the cause that occurred two decades ago [22].

Bottom Line: The recent resurgence of mumps is caused by multiple factors: suboptimal effectiveness of the current mumps vaccines, use of the Rubini strain vaccine, waning immunity in the absence of natural boosting due to the marked reduction in the mumps incidence, genotype mismatch between the vaccine and circulating mumps virus strains, and environmental conditions that foster intense exposures.Despite the suboptimal vaccine effectiveness in outbreak settings, maintaining the high vaccine coverage is an important strategy to prevent mumps outbreaks, given that the routine use of mumps vaccines has substantially reduced the incidence of mumps and its complications as compared with that in the pre-vaccine era.Furthermore, more effective mumps vaccines need to be developed in the future.

View Article: PubMed Central - PubMed

Affiliation: Division of Infectious Diseases, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.

ABSTRACT
Routine vaccination against mumps has markedly reduced its incidence. However, the incidence of mumps continuously has increased since 2007. In 2013, a large mumps epidemic occurred in Korea, and this epidemic is still an ongoing problem. This epidemic occurred primarily in school settings and affected vaccinated adolescents, predominantly male students. The recent resurgence of mumps is caused by multiple factors: suboptimal effectiveness of the current mumps vaccines, use of the Rubini strain vaccine, waning immunity in the absence of natural boosting due to the marked reduction in the mumps incidence, genotype mismatch between the vaccine and circulating mumps virus strains, and environmental conditions that foster intense exposures. Containment of mumps outbreaks is challenging because the sensitivity of diagnostic tests is low among vaccinees and control measures are less efficient because of the inherent nature of the mumps virus. Despite the suboptimal vaccine effectiveness in outbreak settings, maintaining the high vaccine coverage is an important strategy to prevent mumps outbreaks, given that the routine use of mumps vaccines has substantially reduced the incidence of mumps and its complications as compared with that in the pre-vaccine era. In order to control the current mumps epidemic and prevent further outbreaks, we need to better understand the dynamics of mumps among vaccinated populations and the changing epidemiology in Korea. Concerted efforts should be made to systematically monitor the immunization status of the Korean population and to improve diagnosis efficiency. Furthermore, more effective mumps vaccines need to be developed in the future.

No MeSH data available.


Related in: MedlinePlus