Genetic characteristics of mumps viruses isolated in Korea from 2007 to 2012

[Genetic diversity of the mumps viruses (Paramyxoviridae: Orthorubulavirus: Mumps orthorubulavirus): an overview]

Mumps is an infectious disease controlled by specific vaccine prophylaxis. To date, its social and epidemiological significance remains high. This is evidenced by the process of developing and implementing into the health care practices of many countries a set of measures for surveillance of mumps. In the Russian Federation, the National Program «Elimination of measles and rubella and achievement of sporadic morbidity with epidemic mumps in the Russian Federation (2021-2025)» and the national plan for its implementation were adopted in 2021. The basis for the adoption of these documents was the development of the domestic trivalent vaccine for the prevention of measles, rubella and mumps, Vaktrivir, and the start of its clinical application. The availability of this vaccine will make the epidemiological surveillance of mumps to be a part of the existing system of appropriate measures for measles and rubella. The fulfillment of this set of tasks involves the study of the molecular epidemiology of the mumps virus (MuV) with possible subsequent implementation of its methodology into the surveillance actions. In this connection, this work was aimed at presenting the data on global genetic diversity of MuV as well as its genotyping methods in a systematized form. The analysis of MuV global genetic diversity in different years will be the starting point in the subsequent development of approach to monitoring virus strains circulating in the Russian Federation.

Cross-neutralization between vaccine and circulating wild-type mumps viruses in Korea

Mumps is a contagious disease caused by the mumps virus. It can be prevented using mumps vaccines, administered as a measles-mumps-rubella (MMR) vaccine. For first and second dose immunization, children aged 12-15 months and 4-6 years have been administered this vaccine since 1997 in Korea. Nevertheless, mumps outbreaks still occur in vaccinated populations worldwide. Hence, immunity against these diseases may be attenuated, or there are antigenic differences between currently available vaccine strains and circulating wild-type viruses. After the introduction of national immunization programs in Korea, mumps cases became sporadic. Viral genotypes F, H, and I have emerged since 1998 whereas the vaccine strains belong to genotype A. Here, we compared the amino acid sequences of the haemagglutinin-neuraminidase (HN) gene from wild-type viruses and the mumps vaccine and measured the cross-neutralization titers between them. We selected the F, H, and I wild-type mumps strains circulating in Korea from 1998 to 2016 and analyzed changes in the amino acid sequence of the protein encoded by the HN gene. We measured mumps virus-specific IgG and rapid focus reduction neutralization test (FRNT) titers in Korean isolates and sera obtained from 50 children aged 1-2 years who had been administered a single dose of MMR vaccine. Analysis of the HN protein sequences disclosed no changes in the glycosylation sites but did reveal 4-5 differences between the Korean isolates and the genotype A vaccine strain in terms of the neutralizing epitope sites on their HN proteins. Post-vaccination FRNT titers were significantly lower against genotypes F, H, and I than they were against genotype A. This finding highlights the possibility of a recurrence of mumps outbreaks in vaccinated populations depending on the degree of genetic conservation of the HN gene. Further research into this issue is needed to prevent the resurgence of mumps.

Mumps Outbreaks in Vaccinated Populations-Is It Time to Re-assess the Clinical Efficacy of Vaccines?

History illustrates the remarkable public health impact of mass vaccination, by dramatically improving life expectancy and reducing the burden of infectious diseases and co-morbidities worldwide. It has been perceived that if an individual adhered to the MMR vaccine schedule that immunity to mumps virus (MuV) would be lifelong. Recent mumps outbreaks in individuals who had received two doses of the Measles Mumps Rubella (MMR) vaccine has challenged the efficacy of the MMR vaccine. However, clinical symptoms, complications, viral shedding and transmission associated with mumps infection has been shown to be reduced in vaccinated individuals, demonstrating a benefit of this vaccine. Therefore, the question of what constitutes a good mumps vaccine and how its impact is assessed in this modern era remains to be addressed. Epidemiology of the individuals most affected by the outbreaks (predominantly young adults) and variance in the circulating MuV genotype have been well-described alluding to a collection of influences such as vaccine hesitancy, heterogeneous vaccine uptake, primary, and/or secondary vaccine failures. This review aims to discuss in detail the interplay of factors thought to be contributing to the current mumps outbreaks seen in highly vaccinated populations. In addition, how mumps diagnoses has progressed and impacted the understanding of mumps infection since a mumps vaccine was first developed, the limitations of current laboratory tests in confirming protection in vaccinated individuals and how vaccine effectiveness is quantified are also considered. By highlighting knowledge gaps within this area, this state-of-the-art review proposes a change of perspective regarding the impact of a vaccine in a highly vaccinated population from a clinical, diagnostic and public perspective, highlighting a need for a paradigm shift on what is considered vaccine immunity.

Viral etiology of sporadic cases of parotitis among children in Korea during 2013-2014

Recent years have seen a high incidence of mumps, which is generally diagnosed based on clinical features, especially parotitis, without laboratory confirmation in Korea. To better understand the epidemiology of mumps in Korean children, we investigated sporadic suspected mumps cases with parotitis. In total, 237 buccal swabs or throat swabs collected from children with parotitis who had been clinically diagnosed with mumps were tested using real-time PCR for the detection of six viruses (Epstein-Barr virus, Human herpesvirus 6, Mumps virus, Human parainfluenza virus-1, -2, -3, Human adenovirus, Human bocavirus). Among 237 parotitis cases, 87 (36.7%) were positive for at least one virus; a single infection was observed in 73 (83.9%) cases, and co-infections were detected in 14 (16.1%) cases. Epstein-Barr virus was most frequent (20.7%), followed by human herpesvirus 6 (8.0%), mumps virus (5.5%), human parainfluenza virus-3 (4.6%), human adenovirus (4.2%), and human bocavirus (0.4%). These data suggested that the sporadic suspected mumps in the children might be related to other respiratory viruses rather than to the mumps virus. Our findings also indicate the limitation of clinical diagnosis without laboratory confirmation for mumps and thus highlight the importance of laboratory testing in suspected mumps cases.