Matched case-control study of effectiveness of live, attenuated S79 mumps virus vaccine against clinical mumps

Attenuated MuV-S79 as vector stably expressing foreign gene

BACKGROUND

To describe mumps virus (MuV) used as a vector to express enhanced green fluorescent protein (EGFP) or red fluorescent protein (RFP) genes.

METHODS

Molecular cloning technique was applied to establish the cDNA clones of recombinant mumps viruses (rMuVs). rMuVs were recovered based on our reverse genetic system of MuV-S79. The properties of rMuVs were determined by growth curve, plaque assay, fluorescent microscopy and determination of fluorescent intensity.

RESULTS

Three recombinant viruses replicated well in Vero cells and similarly as parental rMuV-S79, expressed heterologous genes in high levels, and were genetically stable in at least 15 passages.

CONCLUSION

rMuV-S79 is a promising platform to accommodate foreign genes like marker genes, other antigens and immunomodulators for addressing various diseases.

Establishment of an efficient reverse genetic system of Mumps virus S79 from cloned DNA

BACKGROUND

Mumps is a common type of respiratory infectious disease caused by mumps virus (MuV), and can be effectively prevented by vaccination. In this study, a reverse genetic system of MuV that can facilitate the rational design of safer, more efficient mumps vaccine candidates is established.

METHODS

MuV-S79 cDNA clone was assembled into a full-length plasmid by means of the GeneArt™ High-Order Genetic Assembly System, and was rescued via reverse genetic technology. RT-PCR, sequencing, and immunofluorescence assays were used for rMuV-S79 authentication. Viral replication kinetics and in vivo experimental models were used to evaluate the replication, safety, and immunogenicity of rMuV-S79.

RESULTS

A full-length cDNA clone of MuV-S79 in the assembly process was generated by a novel plasmid assemble strategy, and a robust reverse genetic system of MuV-S79 was successfully established. The established rMuV-S79 strain could reach a high virus titer in vitro. The average viral titer of rMuV-S79 in the lung tissues was 2.68 ± 0.14 log₁₀PFU/g lung tissue, and rMuV-S79 group did not induce inflammation in the lung tissues in cotton rats. Neutralizing antibody titers induced by rMuV-S79 were high, long-lasting and could provide complete protection against MuV wild strain challenge.

CONCLUSION

We have established a robust reverse genetic system of MuV-S79 which can facilitate the optimization of mumps vaccines. rMuV-S79 rescued could reach a high virus titer and the safety was proven in vivo. It could also provide complete protection against MuV wild strain challenge.

Dynamic transmission model of routine mumps vaccination in Japan

The mumps vaccine is not included in the national immunisation programme (NIP) of approximately 80 countries including Japan. To investigate the vaccine's cost-effectiveness, we developed a dynamic transmission model for routine one- and two-dose mumps vaccination programs in Japan. We calculated the incremental cost-effectiveness ratio compared with a current programme over a projected 50-year period. We created a Japanese population model and performed dynamic simulation to estimate the number of patients enrolled in the current programme, the routine one-dose programme, and the routine two-dose programme over the next 50 years using the Berkeley Madonna program. We estimated the medical and social costs of natural mumps infections and vaccinations to analyse cost-effectiveness. Finally, we performed a sensitivity analysis with parameters including vaccine cost, vaccine efficacy, medical costs per case, social costs per case, incidence of adverse events and discount rate. Base case analysis showed that both the one-dose and two-dose programmes predominated and that quality-adjusted life years (QALYs) were saved, compared with the current programme. The medical costs, total cost and QALYs saved during the study period in the two-dose programme compared with the current programme were 217 billion JPY, 860 billion JPY and 184 779, respectively. The two-dose programme surpassed the one-dose programme throughout the study period. In all the scenarios of the sensitivity analysis, two-dose vaccination was better than the one-dose programme. This simulation confirmed that the routine two-dose vaccination programme was more cost-effective and QALY-saving than either the one-dose programme or the current programme. Because of the variability of the results between the various models, further simulations with different models should be conducted.

Mumps outbreaks: A problem in need of solutions

OBJECTIVES

To discuss what is presently known about recent mumps outbreaks and what solutions can be suggested to ensure more complete protection against mumps.

METHODS

PubMed was used to search for all of the studies published over the last 15 years using the key words "mumps" or "mumps virus" or "mumps vaccine". More than 1500 articles were found, but only those published in English or providing evidence-based data were included in the evaluation.

RESULTS

Prevention of mumps remains an unsolved problem. Available vaccines are effective but the protection they evoke declines over time. The use of booster doses can control outbreaks but it is not precisely defined whether they can prevent them. The rapid decline of antibody levels could limit the impact of the introduction of a third dose in the recommended immunization schedule. Furthermore, in most of the areas, mumps viral strains that are genetically different from those included in the vaccines are emerging and this might favour vaccine escape. However, also for this problem, its real relevance in favouring outbreak development is not precisely defined.

CONCLUSIONS

The true reasons for the development of mumps outbreaks in people with very high vaccination coverage are not clearly understood. The use of a booster dose or the preparation of vaccines containing the emerging serotypes are possible solutions, but both have some limitations. Further studies mainly devoted to improve our knowledge of the immune response to mumps vaccines are needed before long-term effective mumps vaccines can be prepared and outbreaks can be avoided.

Immunogenicity of mumps virus vaccine candidates matching circulating genotypes in the United States and China

Mumps virus (MuV) causes acute infection in humans with characteristic swelling of the parotid gland. While vaccination has greatly reduced the incidence of MuV infection, there have been multiple large outbreaks of mumps virus (MuV) in highly vaccinated populations. The most common vaccine strain, Jeryl Lynn, belongs to genotype A, which is no longer a circulating genotype. We have developed two vaccine candidates that match the circulating genotypes in the United States (genotype G) and China (genotype F). We found that there was a significant decrease in the ability of the Jeryl Lynn vaccine to produce neutralizing antibody responses to non-matched viruses, when compared to either of our vaccine candidates. Our data suggests that an updated vaccine may allow for better immunity against the circulating MuV genotypes G and F.

The relationship between meteorological factors and mumps incidence in Guangzhou, China, 2005-2012:

BACKGROUND

Over the past decade, there have been resurgences and large-scale outbreaks of mumps worldwide. Little evidence is available on the relationship between meteorological factors and the incidence of mumps. We aimed to explore the effects of meteorological factors on mumps incidence.

METHODS

A Poisson regression model combined with a distributed lag non-linear model (DLNM) was used to evaluate the association between meteorological factors and the mumps incidence in Guangzhou, China, 2005-2012.

RESULTS

Nonlinear relationships between meteorological factors, except sunshine hours, and mumps incidence were observed. The relative risks (RRs) of mean temperature, relative humidity and atmospheric pressure were 1.81 (95% confidence interval (CI), 1.41 to 2.32), 1.28 (95% CI, 1.02 to 1.59), and 0.80 (95% CI, 0.67 to 0.95) comparing the 99th percentile to the median of their own, respectively. For wind velocity, the RR was 0.70 (95%CI, 0.54 to 0.91) comparing the 1st percentile to the median. The hot effect and cold effect were larger in females than in males, and the hot effect increased with age.

CONCLUSIONS

Mean temperature, relative humidity, wind velocity and atmospheric pressure might be important predictors of the mumps incidence. Tropical cyclone caused a higher increase in mumps cases. Our findings highlight the need to strengthen the awareness of using protective measures during typhoon days and allocating more attention to the susceptible populations during the summer. The two-dose regimen of mumps vaccine should be included in the National Immunization Program schedule, and the catch-up vaccination campaigns should be promoted among adults.

Assessing mumps outbreak risk in highly vaccinated populations using spatial seroprevalence data

Mumps is a potentially severe viral infection. The incidence of mumps has declined dramatically in high-income countries since the introduction of mumps antigen-containing vaccines. However, recent large outbreaks of mumps in highly vaccinated populations suggest waning of vaccine-induced immunity and primary vaccine failure. In this paper we present a simple method for identifying geographic regions with high outbreak potential, demonstrated using 2006 mumps seroprevalence data from Belgium and Belgian vaccination coverage data. Predictions of the outbreak potential in terms of the effective reproduction number in future years signal an increased risk of new mumps outbreaks. Literature reviews on serological information for both primary vaccine failure and waning immunity provide essential information for our predictions. Tailor-made additional vaccination campaigns would be valuable for decreasing local pockets of susceptibility, thereby reducing the risk of future large-scale mumps outbreaks.

Measles epidemic from 1951 to 2012 and vaccine effectiveness in Guangzhou, southern China

BACKGROUND

Since the National Expanded Program on Immunization was implemented in China, considerable progress has been made in reducing the incidence of measles. However, the incidence of measles increased again in 2004. Few post-marketing studies on measles vaccine effectiveness were reported in China. In this study, we aimed to describe the measles epidemic and to evaluate the effectiveness of the measles vaccine in Guangzhou, southern China.

METHODS

Based on the surveillance data for measles, we investigated the epidemiology during different periods between 1951 and 2012. We analyzed the clinical characteristics of laboratory-confirmed cases of measles between 2009 and 2012 and conducted a case-control study using test-negative cases as controls. We determined the protective effect of measles vaccine.

RESULTS

The highest annual incidence in Guangzhou was 2187.15/100,000 in 1964, and the lowest was 0.32/100,000 in 2011. The average incidence of measles from 1951 to 2012 was 306.27/100,000. There was a significant tendency of decline in recent years. From 2009 to 2012, there are 700 laboratory-confirmed cases were reported with an average onset age of 2.5 (median) years. The non-vaccinated target population (age<8 months and ≥ 15 years) accounted for 56.7% of the cases. The transient (non-resident) population accounted for 51.3% of the cases. Fewer cases were observed in the population targeted for measles vaccine (aged 8 months to 14 years). The effectiveness of a single dose of the measles vaccine was 89.1% (95% confidence interval (CI), 44.5-97.9), and the effectiveness of ≥ 2 doses of the measles vaccine was 97.8% (95% CI, 88.3-99.6) in children aged 8 months to 14 years old.

CONCLUSIONS

There is a significant overall decline in the incidence of measles (including clinical and laboratory confirmed cases) in the measles vaccine targeted population in Guangzhou. Two doses of measles vaccine are more effective than one dose in preventing measles in China. In order to accelerate the elimination of measles, vaccination should also be given to the transient and the non-vaccine targeted population.

Effectiveness of one dose of mumps vaccine against clinically diagnosed mumps in Guangzhou, China, 2006-2012

Although mumps-containing vaccines were introduced in China in 1990s, mumps continues to be a public health concern due to the lack of decline in reported mumps cases. To assess the mumps vaccine effectiveness (VE) in Guangzhou, China, we performed a 1:1 matched case-control study. Among children in Guangzhou aged 8 mo to 12 y during 2006 to 2012, we matched one healthy child to each child with clinically diagnosed mumps. Cases with clinically diagnosed mumps were identified from surveillance sites system and healthy controls were randomly sampled from the Children's Expanded Programmed Immunization Administrative Computerized System in Guangzhou. Conditional logistic regression was used to calculate VE. We analyzed the vaccination information for 1983 mumps case subjects and 1983 matched controls and found that the overall VE for 1 dose of mumps vaccine, irrespective of the manufacture, was 53.6% (95% confidence interval [CI], 41.0-63.5%) to children aged 8 mo to 12 y. This post-marketing mumps VE study found that immunization with one dose of the mumps vaccine confers partial protection against mumps disease. Evaluation of the VE for the current mumps vaccines, introduction of a second dose of mumps vaccine, and assessment of modifications to childhood immunization schedules is essential.

Effectiveness of seasonal influenza vaccine against clinically diagnosed influenza over 2 consecutive seasons in children in Guangzhou, China: a matched case-control study

Influenza vaccine has to be reformulated each year due to the ever-changing antigenicity of the influenza virus. However, few post-licensure studies of influenza vaccine are available in China. We aimed to measure the effectiveness of seasonal influenza vaccine during 2 consecutive seasons. Among children in Guangzhou aged 6 to 59 mo in 2010-2012, we matched each child with clinically diagnosed influenza to 3 healthy children. Cases with clinically diagnosed influenza were identified from surveillance system. Healthy controls were randomly sampled from the Children's Expanded Programmed Immunization Administrative Computerized System. Conditional logistic regression was used to calculate vaccine effectiveness (VE). A total of 275 matched sets of subjects were included. VE levels against clinically diagnosed influenza for both seasons combined was 47.4% [95% confidence interval (CI), 8.5-69.8%] for full vaccination for children aged 6-35 mo, 33.6% (95% CI, 5.4-53.5%) for any vaccination for children aged 6-59 mo, respectively. VE by time since vaccination for any vaccination was 34.6% (95% CI, 4.7-55.2%) in 0-5 mo, and no protection was observed in 6-11 mo. Annual, full and timely vaccination should be encouraged for children.

Effectiveness of the Lanzhou lamb rotavirus vaccine against gastroenteritis among children

The Lanzhou lamb rotavirus (LLR) vaccine has been in use in China since 2000. This study evaluated this vaccine's effectiveness using a case-control design in Guangzhou. In the study area, there were 3130 laboratory-confirmed rotavirus gastroenteritis cases in children between 2 and 35 months old from 2009 to 2011. A total of 3607 controls were also enrolled in this study. Of the subjects, 970 (14.4%) had received 1 dose of the LLR vaccine. Because of the low vaccination rate, we only obtained an effectiveness of 44.3% (95% CI, 28.4-56.7%) for children 9-11 months old, 52.8% (40.8-62.3%) for children 12-17 months old, and 51.8% (11.6-73.8%) for children 18-35 months old for one dose. This post-marketing study found that one dose of the LLR vaccine confers partial protection when given to children between 9 and 35 months old. Therefore, earlier immunization and the administration of the full immunization regimen should be encouraged.

Seasonal influenza vaccine effectiveness among children aged 6 to 59 months in southern China

In China the protective effect of seasonal influenza vaccine has only been assessed in controlled clinical trials and proven to be highly effective. However, the post-licensure effectiveness of influenza vaccine has not been examined. In our study all influenza cases from the 19 surveillance sites in Guangzhou were laboratory confirmed during 2009 and 2010. Controls were randomly selected from children aged 6 to 59 months in the Children's Expanded Programmed Immunization Administrative Computerized System. 2529 cases and 4539 controls were finally enrolled. After adjusting for gender, age and area of residence, the vaccine effectiveness of full vaccination was 51.79% and 57.78% in the 2009 and 2010 influenza season, respectively. Partial vaccination provided 39.38% and 35.98% protection to children aged 24 to 59 months in 2009 and 2010, respectively, and no protective effect was observed among younger children. Full vaccination is highly protective and partial vaccination is protective for older children. Influenza vaccination in general should be encouraged, and full vaccination should be particularly encouraged because its protective effect is much stronger than that of partial vaccination.

Recent mumps outbreaks in vaccinated populations: no evidence of immune escape

Recently, numerous large-scale mumps outbreaks have occurred in vaccinated populations. Clinical isolates sequenced from these outbreaks have invariably been of genotypes distinct from those of vaccine viruses, raising concern that certain mumps virus strains may escape vaccine-induced immunity. To investigate this concern, sera obtained from children 6 weeks after receipt of measles, mumps, and rubella (MMR) vaccine were tested for the ability to neutralize a carefully selected group of genetically diverse mumps virus strains. Although the geometric mean neutralizing antibody titer of the sera was lower against some virus strains than others, all viruses were readily neutralized, arguing against immune escape.

The use of immunization registry-based data in vaccine effectiveness studies

Vaccine effectiveness (VE) studies provide a measure of population-based vaccine performance by combining immunization history data with rates of disease incidence. This review assessed the feasibility of using electronic immunization registry data sources in VE studies. Electronic databases were searched through January 31, 2010. Out of 17 studies, only one paper assessed data accuracy (71%), and three papers assessed population coverage of the registry (estimates ranged from 25% to 90%). This review shows that registry-based data sources can be used to conduct VE studies in a variety of settings and populations. However, we found little information regarding the quality of this data source in VE studies and future evaluations should investigate their reliability, accuracy, and potential bias.