Development of varicella vaccine in Japan and future prospects

Association Between Child Varicella Vaccination and Zoster in Household Adults: A Retrospective Japanese Cohort Study

AIM

Some countries are hesitant to implement routine varicella vaccination for children because of concerns over the exogenous boosting hypothesis, which suggests that vaccinating children may increase herpes zoster cases in adults. However, substantial evidence supporting this hypothesis is lacking. This study assessed the association between a child's varicella vaccination status and herpes zoster occurrence in adults in the same household.

METHODS

This retrospective cohort study analysed data from a Japanese city between April 2014 and December 2022. We included individuals aged ≥ 18 years living in households with a single child eligible for varicella vaccination. Children's vaccination status was categorised as unvaccinated, first-dose vaccinated or second-dose vaccinated. Cox regression analysis with time-dependent exposure assessed herpes zoster incidence in adults.

RESULTS

Among 4023 eligible individuals, 136 (3.4%) developed herpes zoster over the median follow-up of 552 days. Neither the first nor the second dose of varicella vaccine in children was significantly associated with an increased risk of herpes zoster in adults (hazard ratio 1.24 [95% confidence interval, 0.69-2.23] for the first dose and 1.51 [0.87-2.62] for the second dose).

CONCLUSION

Varicella vaccination in households with a single child was not significantly associated with an increased risk of herpes zoster in adults.

Varicella and Zoster Vaccination Strategies in Immunosuppressed Pediatric Transplant Recipients

The varicella vaccine has prevented varicella in hundreds of thousands of patients since its establishment in 1974. It stimulates both humoral and cell-mediated immunity to produce an immune response that helps protect against the disease (not necessarily the infection). Serious sequala of varicella including pneumonia, hepatitis, and encephalitis can occur, with higher incidence in immunosuppressed individuals than in the general population. Patients who are not immunosuppressed should receive routine varicella vaccinations. For those who have not completed the series or are significantly distant from their last immunization, serologic testing may be considered. In pre-transplant patients, live-attenuated vaccines should ideally be administered at least four weeks before transplantation. Case studies have documented instances of patients requiring treatment for varicella after receiving a transplant within four weeks of vaccination.

Ramsay Hunt Syndrome With Multiple Cranial Neuropathies, Meningitis, and Subsequent Brainstem Encephalitis: A Case Report

We present a case of Ramsay Hunt syndrome in a previously healthy 49-year-old male, complicated by ipsilateral glossopharyngeal, vagus, accessory, and hypoglossal nerve palsies, along with meningitis. Despite a course of antiviral therapy and steroids for meningitis, the patient experienced a relapse, developing varicella-zoster virus (VZV) brainstem encephalitis after an initial period of stability. Hunt syndrome can be encountered in otolaryngology and internal medicine, dermatology, and other specialties. We report a case of Ramsay Hunt syndrome complicated by multiple cranial neuropathies and Hunt syndrome-associated meningitis and encephalitis, accompanied by a literature review.

An Introduction to the Japanese Immunization Program: Past, Present, and Future Perspectives

In Japan, immunization is regulated by the Immunization Law, enacted shortly after World War II ended. It has been subsequently revised in response to social changes; however, after public health conditions improved, adverse events following immunization have received more public attention than the effectiveness of vaccination. This kind of public opinion had a major impact on the immunization program, leading to a so-called "vaccine gap" around a decade ago, that is, the less availability of vaccines for routine vaccination as compared with other countries. However, in recent years, several vaccines have been approved and are being routinely administered with the same schedule as in other countries. National immunization programs are influenced by various factors, such as cultures, customs, habits and ideas. This paper summarizes the status of immunization schedule and practices in Japan, process of policymaking, and possible future issues.

Anti-varicella-zoster virus antibody titers and seroprotection status from before the first dose of varicella vaccination to before entering elementary school in one region in Japan

OBJECTIVE

We aimed to examine changes in anti-varicella-zoster virus (VZV) antibody titers and seroprotection status from before the first dose of vaccination to before 7 years old entering elementary school in children who received the routine two-dose varicella vaccination.

METHODS

Participants were 37 healthy children who received the routine two-dose varicella vaccination at our hospital. A total of five serum samples per child were collected immediately before and 4-6 weeks after each dose of the vaccination and in the year before entry to elementary school. We measured anti-VZV antibody titers by immune adherence hemagglutination (IAHA) method and glycoprotein-based enzyme-linked immunosorbent assay (gpELISA). A positive antibody titer and the seroprotection level were set as ≥2-fold and ≥16-fold, respectively, for IAHA antibody and as ≥50 units and ≥105 units, respectively, for gpELISA-IgG antibody.

RESULTS

The rates of IAHA antibody positivity in the five samples (in order of collection) were 0%, 65%, 38%, 100%, and 59%, and the rates of seroprotection were 0%, 43%, 8%, 100%, and 43%. The rates of gpELISA-IgG antibody positivity were 8%, 81%, 89%, 100%, and 100%, and the rates of seroprotection were 5%, 54%, 70%, 100%, and 89%. The mean IAHA antibody titer and mean gpELISA-IgG antibody titer before entering elementary school were both lower than the respective titers obtained after the second vaccination (both p < 0.01).

CONCLUSIONS

Routine two-dose varicella vaccination leads to good antibody production, but titers of acquired antibodies decrease before children enter elementary school.

Analysis of the reliability of rapid diagnostic tests for varicella, including breakthrough cases

In the era of universal varicella vaccination, diagnosis of varicella is challenging, especially for breakthrough cases. We sought to clarify the reliability of direct varicella-zoster virus (VZV) loop-mediated isothermal amplification (LAMP) and DermaQuick® VZV using the immunochromatography technique as rapid diagnostic tests for varicella. In addition, the usefulness of saliva as a sample type for direct LAMP was investigated. Among the 46 enrolled patients with suspected VZV infection, 31 patients (67.3%) were positive for the nucleic acid test based on real-time PCR from skin swab samples. Direct LAMP of skin swabs was positive in 29 (63.0%) of 46 patients. DermaQuick® VZV was positive in 25 (54.3%) of 46 patients. VZV DNA was detected in only 48.4% of oral swabs with the direct LAMP method. With real-time polymerase chain reaction (PCR) as the standard for diagnosing varicella, the sensitivity and specificity of DermaQuick® VZV were 80.7% and 100%, respectively. The sensitivity and specificity of direct LAMP from skin swabs were 93.6% and 100%, respectively. The sensitivity and specificity of real-time PCR for DNA extracted from oral swabs were 74.2% and 93.3%, respectively. Thus, oral swab samples are not suitable for breakthrough varicella diagnosis. Although DermaQuick® VZV is considered the most convenient point-of-care test for varicella, its sensitivity and specificity were lower than those of direct VZV LAMP.

Long-term vaccine efficacy of a 2-dose varicella vaccine in China from 2011 to 2021: A retrospective observational study

Objective

A 2-dose varicella vaccine immunization strategy has been implemented in many cities in China, but there is few evidence on a long-term evaluation of the efficacy of the 2-dose varicella vaccine from China. This study aims to assess the long-term vaccine efficacy of the two doses varicella vaccine and analysis of its influencing factors.

Methods

A retrospective study was carried out in 837,144 children born between 2011 and 2017 in Ningbo, Easten China. The logistic regression was performed to estimate varicella vaccine effectiveness (VE).

Results

The overall VE of 2 doses of varicella vaccine compared without the vaccine was 90.31% (89.24-91.26%), and the overall incremental VE of 2 doses of varicella vaccine compared to the 1-dose was 64.71% (59.92-68.93%). Moreover, the varicella vaccination age of the second dose and the interval between 2 doses were both associated with VE. The VE compared to that without the vaccine in children vaccinated at <4 years old was 91.22% (95%CI: 90.16-92.17%) which was higher than in children vaccinated at ≥4 years old (VE: 86.79%; 95%CI: 84.52-88.73). And the effectiveness of the vaccine was 93.60% (95%CI: 92.19-94.75%) in children with the interval of the 2 doses ≤ 24 months significantly higher than in children with the interval of ≥36 months (VE: 85.62%, 95%CI: 82.89-87.91%).

Conclusions

This study provides evidence for long-term VE of the 2-dose varicella vaccine and the better age for 2-dose vaccination and the interval between 2 doses of the vaccine in China.

Immunological characteristics of MAV/06 strain of varicella-zoster virus vaccine in an animal model

BACKGROUND

Varicella-zoster virus (VZV) is a pathogen that causes chickenpox and shingles in humans. Different types of the varicella vaccines derived from the Oka and MAV/06 strains are commercially available worldwide. Although the MAV/06 vaccine was introduced in 1990s, little was known about immunological characteristics.

RESULTS

Here, we evaluated B and T cell immune response in animals inoculated with the Oka and MAV/06 vaccines as well as a new formulation of the MAV/06 vaccine. A variety of test methods were applied to evaluate T and B cell immune response. Plaque reduction neutralization test (PRNT) and fluorescent antibody to membrane antigen (FAMA) assay were conducted to measure the MAV/06 vaccine-induced antibody activity against various VZVs. Glycoprotein enzyme-linked immunosorbent assay (gpELISA) was used to compare the degree of the antibody responses induced by the two available commercial VZV vaccines and the MAV/06 vaccine. Interferon-gamma enzyme-linked immunosorbent spot (IFN-γ ELISpot) assays and cytokine bead array (CBA) assays were conducted to investigate T cell immune responses. Antibodies induced by MAV/06 vaccination showed immunogenicity against a variety of varicella-zoster virus and cross-reactivity among the virus clades.

CONCLUSIONS

It is indicating the similarity of the antibody responses induced by commercial varicella vaccines and the MAV/06 vaccine. Moreover, VZV-specific T cell immune response from MAV/06 vaccination was increased via Th1 cell response. MAV/06 varicella vaccine induced both humoral and cellular immune response via Th1 cell mediated response.

Implementing vaccination policies based upon scientific evidence in Japan

The theme of the 24th Annual Meeting of the Japanese Society for Vaccinology was “Sustainable Future Medical Care Created by Vaccines.” This theme includes topics such as the proposal to reduce the medical costs incurred by societies with aging populations through prophylactic vaccination. The coronavirus disease 2019 (COVID-19) pandemic alerted us to the important roles that preventive measures, such as vaccines, play in fighting infectious diseases. In order to inform the public of the benefits of vaccines, it is important to provide society with information regarding new vaccine developments, adjuvants, the cost–benefit ratio of vaccine introduction, and vaccine effectiveness and safety. Clinical research is essential for obtaining evidence of vaccine effectiveness and safety. The United States Centers for Disease Control and Prevention (CDC) conducts active surveillance in defined areas before and after the introduction of vaccines and documents the reduction in infection rates as a measure of vaccine effectiveness. However, vaccine efficacy and side effects may vary by country and ethnicity. Therefore, it is necessary for individual countries to develop their own evidence-based surveillance programs. We have studied vaccine efficacy and documented side-effects observed in patients for the varicella and rotavirus vaccines in Japan. This review outlines the importance of providing scientific evidence for vaccine effectiveness and safety.

Changes in epidemiological characteristics and sero-prevalence against the varicella zoster virus in school-age children after the introduction of a national immunization program in Japan

A national immunization program using two doses of live attenuated varicella vaccine was introduced for children aged one to two years in Japan in October 2014. Varicella cases declined after 2014, and immunological status against varicella among vaccinated children changed in post-vaccination era. A retrospective observational study of anti-varicella antibody seroprevalence, varicella vaccination status, and history of varicella among 528 students in the first grade of elementary school was conducted. The percentage of students who received at least a single dose of varicella vaccination increased from 67% (187 of 279 students) in 2007-2008 to 91% (226 of 249 students) in 2017. Students with a history of varicella decreased from 114 of 279 (41%) in 2007-2008 to 48 of 249 (19%, P < .01) in 2017. Among them, the rate of breakthrough varicella after a single dose of vaccine in students with a history of varicella significantly increased from 38% (43 of 114 students) in 2007-2008 to 58% (28 of 48 students) in 2017 (P < .05). The antibody-positive rate significantly decreased from 50% among subjects without varicella zoster who received a single dose (95%CI: 41-58%) in 2007-2008 to 29% (95%CI: 21-38%) in 2017 (P < .01). The antibody-positive rate among students without varicella history who received two doses of vaccine was only 43% (95%CI: 32-55%) in 2017. The number of varicella infections and antibody-positive rate among students without history of varicella who received varicella vaccination decreased after the introduction of a national immunization program.

A Protein Assembly Hypothesis for Population-Specific Decrease in Dementia with Time

A recent report in the journal, Neurology, documents age-normalized, nation-specific (e.g., United States and Western Europe), progressive decrease of dementia, beginning about 25 years ago. This observation has, thus far, not had explanation. We begin our proposed explanation with the following previous disease construct. (1) Some dementia is caused by innate immune over-response to infections. (2) The innate immune over-response occurs via excessive conversion of amyloid protein to α-sheet conformation. (3) This conversion evolved to inhibit invading microbes by binding microbe-associated α-sheet, e.g., in hyper-expanded capsid intermediates of some viruses. The rarity of human α-sheet makes this inhibition specific for microbial invaders. As foundation, here we observe directly, for the first time, extreme, sheet-like outer shell thinness in a hyper-expanded capsid of phage T3. Based on phage/herpesvirus homology, we propose the following. The above decrease in dementia is caused by varicella-zoster virus (VZV) vaccination, USFDA-approved about 25 years ago; VZV is a herpesvirus and causes chickenpox and shingles. In China and Japan, a cotemporaneous non-decrease is explained by lower anti-VZV vaccination. Co-assembly extension of α-sheet is relatively independent of amino acid sequence. Thus, we project that additional dementia is suppressible by vaccination against other viruses, including other herpesviruses.

Evaluation of immunogenicity, safety and breakthrough following administration of live attenuated varicella vaccine in two doses three months apart regimen in Indian children

Background:

In India, where varicella outbreaks are reported at a younger age, a two-dose vaccine schedule administered at an early age could be highly efficacious in preventing varicella infection. The aim of this study was to evaluate the immunogenicity and safety of live attenuated varicella vaccine (VR 795 Oka strain) in a two-dose, 3 months apart regimen.

Methodology:

Healthy children (⩾ 12 months and ⩽12 years; mean age: 4.4 years) of either sex were included. Geometric mean titers (GMT) were measured at baseline and 28 days post first- and second-dose, and seroprotection rates were measured 28 days post first and second dose. The incidence of breakthrough (BT) infections post vaccination was determined from 42 days post first and second dose of vaccine up to 12 months. Adverse events (AEs) were monitored and recorded throughout the study period.

Results:

Of 305 subjects enrolled, 217 were seronegative. The seroconversion rate (a change from a seronegative to a seropositive condition) was 93.3% post first-dose and 100% post two-doses. High levels (9 times) of GMT were reported since post first-dose to post second-dose in children aged 12–18 months, 18–60 months (99.43%); and in and above 60 months (99.02%). The extent of rise of anti-VZV IgG antibody titer post 28 days of first-dose at two-fold, three-fold and four-fold rise was 93.39%, 90.56% and 80.66%, respectively and 100% 4-fold rise post second-dose. A single case, a day after the first-dose of vaccination of mild BT infection, was observed after close contact with a severe case. AEs were mild and none of the serious AEs were related to the study drug.

Conclusion:

The two-dose schedule of varicella vaccine was safe and immunogenic when given 3 months apart. However, further comparative studies and follow up for both dosing schedules are needed to validate the advantage of early dosing.

Reliability of direct varicella zoster virus loop-mediated isothermal amplification method for rapid diagnosis of breakthrough varicella

BACKGROUND

Since patients with breakthrough varicella (BV) have mild symptoms, clinical diagnosis is difficult. In high vaccine coverage area, as BV occurs sporadically, point of care test is required for controlling varicella outbreak. In this study, the reliability of varicella zoster virus (VZV)-loop mediated isothermal amplification (LAMP) was evaluated for the rapid diagnosis of BV.

STUDY DESIGN

A total of 328 swab samples collected from patients with suspected varicella were analyzed. For the laboratory diagnosis of varicella, VZV real-time PCR was carried out using DNA extracted from swab samples. Swab samples without DNA extraction were used for VZV-LAMP(direct-LAMP).

RESULTS

VZV infection was diagnosed by real-time PCR in 285 cases, including 105 natural varicella cases and 180 BV cases. VZV DNA was detected in 250 (87.8%) of the 285 cases by direct-LAMP. The presence and duration of fever, number of skin eruptions, and VZV DNA load were significantly lower in BV than natural varicella. The sensitivity of direct-LAMP for the diagnosis of varicella and BV was 93.3% and 84.4%, respectively.

CONCLUSIONS

Direct LAMP was considered to be useful for rapid diagnosis of BV as it has several advantages such as low cost, ease and rapidity, as compared to real time PCR.

Altered immunogenicity of 23-valent pneumococcal polysaccharide vaccine in elderly patients with diabetes who revealed lower responses to concomitant administration of BIKEN varicella zoster vaccine: Results of post hoc analysis of a randomized double-blind trial

AIMS

This double-blind randomized controlled study of 52 elderly patients with diabetes assessed cell-mediated immunity and safety of BIKEN varicella-zoster vaccine (BVZV). Cellular and humoral responses to VZV at 3 months after BVZV and 23-valent polysaccharide pneumococcal vaccine (PPSV23) vaccination elicited poor results. Post-hoc analyses assessed the effects of immunogenicity of PPSV23.

METHODS

Using standardized enzyme-linked immunosorbent assay, pneumococcal 6B and 23F serotype-specific immunoglobulin G (IgG)-binding antibody concentrations were measured in stored samples retrospectively before administration and 3 months after. Responders increased more than twofold in at least one serotype-specific IgG.

RESULTS

The geometric mean concentration ratio (GMCR) of serum anti-pneumococcal 6B IgG was 1.76 (95%C.I.: 0.58, 5.34) in patients receiving concurrent PPSV23 and BVZV, compared to 2.39 (95%C.I.: 0.53, 10.76) in patients receiving PPSV23 and placebo (P = .055). The GMCR of serum anti-pneumococcal 23F IgG was 2.54 (95%C.I.: 0.57, 11.43) in PPSV23/BVZV vaccinees compared to 3.34 (95%C.I.: 0.84, 12.92) in PPSV23/placebo vaccinees (P = .424). Responder rates, those who developed antibodies to either/both serotypes, were 68% in the BVZV group and 85% in the placebo group (P = .007).

CONCLUSIONS

Results suggest that concurrent administration of BVZV influenced humoral responses to PPSV23 in elderly subjects with diabetes.

Associations of Perceived Mental Stress, Sense of Purpose in Life, and Negative Life Events With the Risk of Incident Herpes Zoster and Postherpetic Neuralgia: The SHEZ Study

In the present population-based prospective study, we examined the associations of psychosocial factors with the incidence of herpes zoster (HZ) and postherpetic neuralgia (PHN). Data were collected from 12,359 participants (≥50 years of age) who answered a self-completed health questionnaire in the Shozu County of Kagawa Prefecture in Japan. During a 3-year follow-up between December 2008 and November 2012, HZ and PHN were diagnosed in 400 and 79 subjects, respectively. We used Cox regression analysis to estimate hazard ratios of incident HZ and PHN according to psychosocial factors, adjusting for age, sex, histories of HZ, cancer, and diabetes, smoking and drinking habits, and time from disease onset to treatment. Men with high levels of mental stress were twice as likely to be at risk for incident HZ. The risk of incident HZ was approximately 60% lower among men and women who reported a high sense of purpose in life. Women who experienced negative life events-particularly changes in their work, living environment, and relationships-had a 2- to 3-fold higher risk of incident PHN. Psychosocial factors such as perceived mental stress, sense of purpose in life, and negative life events may contribute to the development of HZ and PHN in the general population.

Vaccine Development for Varicella-Zoster Virus

Varicella-zoster virus (VZV) is the first and only human herpesvirus for which a licensed live attenuated vaccine, vOka, has been developed. vOka has highly safe and effective profiles; however, worldwide herd immunity against VZV has not yet been established and it is far from eradication. Despite the successful reduction in the burden of VZV-related illness by the introduction of the vaccine, some concerns about vOka critically prevent worldwide acceptance and establishment of herd immunity, and difficulties in addressing these criticisms often relate to its ill-defined mechanism of attenuation. Advances in scientific technologies have been applied in the VZV research field and have contributed toward uncovering the mechanism of vOka attenuation as well as VZV biology at the molecular level. A subunit vaccine targeting single VZV glycoprotein, rationally designed based on the virological and immunological research, has great potential to improve the strategy for eradication of VZV infection in combination with vOka.

Evaluating the effectiveness of the universal immunization program against varicella in Japanese children

OBJECTIVE

Matched case control study was conducted to elucidate the effectiveness of the Oka/Biken vaccine immediately after implementation of the universal immunization program in Japan.

METHODS

Cases were laboratory confirmed varicella patient under 15years of age diagnosed at 14 designated pediatric clinics between September 2015 and September 2016. Controls were selected from patients who visited the same practice for different reasons as the varicella case within 2weeks. Swab samples were collected from varicella suspected patients and molecular diagnostic assays were used to confirm varicella cases. Matched odds ratio were used to calculate vaccine effectiveness (VE).

RESULTS

Varicella zoster virus DNA was detected in 183 (81.3%) of 225 suspected cases. One sample was excluded because it was positive for the Oka vaccine strain (182/225, 80.9%). Three hundred twenty-three control subjects were enrolled. The effectiveness of 1 dose of the Oka/Biken vaccine compared with no vaccine was 76.7% (95% confidence interval [CI]: 58.6-86.9%; P<0.001). The effectiveness of 2 doses of the Oka/Biken vaccine was 94.2% (95% CI: 85.7-97.6%; P<0.001). After adjusting for potential confounding effects, the adjusted VE of 1 and 2 doses of varicella vaccine were 76.9% (95% CI: 58.1-87.3%; P<0.001) and 94.7% (95% CI: 86.0-98.0%; P<0.001), respectively.

CONCLUSIONS

VE of one dose of Oka/Biken varicella vaccine was insufficient to control varicella. Therefore, two doses of Oka/Biken varicella vaccine is significant for controlling varicella in Japan.