Safety of varicella vaccination strategies: An overview of reviews

Immunogenicity and safety of a live attenuated varicella vaccine in children aged 1 to 12 years: A double-blind, randomized, parallel-controlled phase III clinical trial in China

Chickenpox outbreaks frequently occur in collective settings such as kindergartens and schools, posing a significant threat to children's physical and mental health. This study aimed to evaluate the immunogenicity and safety of the freeze-dried live attenuated varicella vaccine (VarV) developed by Beijing Minhai Biotechnology Co. LTD. in healthy participants aged 1-12 years. In this phase III, single-center, randomized, double-blind, active-controlled trial,1,200 healthy participants randomly assigned in a 1:1 ratio to receive one dose of either the test vaccine or the active control vaccine. Venous blood samples were collected before vaccination and 42 days after vaccination, and the fluorescent antibody to membrane antigen (FAMA) assay was used to detect VZV antibody. Adverse events (AEs) observed within 42 days after vaccination and serious adverse events (SAEs) within six months after vaccination were recorded. The seroconversion rates in the test and control groups were 96.79% and 96.43%, respectively, with a difference of 0.36% (95% CI, -1.76%-2.48%). The geometric mean titers (GMTs) were 61.74 and 58.04, respectively, with a difference of 1.06 (95% CI, 0.92-1.23). The lower limits of the 95% CI for the differences in seroconversion rates and GMT ratios between the two groups were greater than their respective pre-set non-inferiority margins. The overall incidence of AEs (p = .0112) in the test group was significantly lower than that in the control group. The freeze-dried live attenuated VarV developed by Beijing Minhai Biotechnology Co. LTD. demonstrated good immunogenicity and higher safety compared to the active control vaccine in healthy participants aged 1-12 years.

Immunogenicity and safety of a live attenuated varicella vaccine in healthy subjects aged between 13 to 55 years: a double-blind, randomized, active-controlled phase III clinical trial in China

BACKGROUND

Adolescents and adults who contract chickenpox are at a higher risk of severe complications. Vaccination with the varicella vaccine (VarV) effectively prevents chickenpox.

RESEARCH DESIGN AND METHODS

In this phase III, single-center, randomized, double-blind, active-controlled trial, 1,200 healthy participants were randomly assigned in a 1:1 ratio to receive two doses of either the test vaccine or the active control vaccine. Varicella-zoster virus (VZV) antibody was detected before vaccination and 42 days after the two doses of vaccination.

RESULTS

The lower limits of the 95% CI for the differences in seroconversion rates and geometric mean titer (GMT) ratios between the two groups were greater than their respective pre-set non-inferiority margins. The overall incidence of Adverse events (AEs) and adverse reactions (ARs) in the test group was significantly lower than those in the control group. Additionally, the incidence rates of swelling and fatigue were lower in the test group compared to the control group after vaccination.

CONCLUSIONS

The test freeze-dried live attenuated VarV demonstrated good immunogenicity and higher safety compared to the active control vaccine in healthy participants aged 13-55 years.

CLINICAL TRIALS REGISTRATION

www.clinicaltrials.gov identifier: NCT06592456.

Surveillance of Adverse Events Following Varicella Vaccine Immunization in Zhejiang Province, China, from 2020 to 2022

Background: China has a high incidence rate of varicella yet a low coverage rate of the varicella vaccine (VarV), with safety concerns being a leading cause of the lack of vaccination willingness. This study aimed to describe VarV-related adverse events following immunization (AEFIs) and analyze their characteristics in Zhejiang, China, 2020-2022. Methods: VarV-related AEFIs in Zhejiang Province from 1 January 2020 to 31 December 2022 were collected through the Chinese National AEFI Information System (CNAEFIS) for a descriptive epidemiological analysis. Results: From 2020 to 2022, a total of 1477 VarV-related AEFI cases were reported (incidence rate: 34.79/100,000). The three most frequently reported clinical symptoms of common adverse reactions were fever, redness, and induration at the vaccination site. The distribution of VarV-related AEFIs varied significantly by age, dose, severity, and season. VarV-related AEFIs were more likely to be non-severe adverse events that occurred in the summer and winter seasons following the first dose of vaccine and among those under 3 years old. The top three regions with the highest incidence rates were Lishui City (59.53/100,000), Quzhou City (41.05/100,000), and Jinhua City (40.43/100,000). Most of the cases achieved full recovery without treatment (96.21%), and the rest were successfully treated without any sequelae. Conclusions: VarV demonstrates a safe profile in Zhejiang Province. Most VarV-related AEFIs are common reactions without requiring treatment, and the rates of rare and severe AEFIs remain low. Consistent monitoring, investigation, and diagnosis are needed to guide future VarV research and vaccination strategy adjustment. Our findings call for more policy changes, such as integrating VarV into China's National Immunization Program and conducting more trials to evaluate the safety and effectiveness of VarV.

Appraisal of umbrella reviews on vaccines

Umbrella reviews are systematic reviews of all systematic reviews on a given question and can provide a higher-level view of current available evidence on broad research topics. Given the importance and possible consequences of the insights derived from umbrella reviews, it is fundamental to ensure accurate, comprehensive reporting and methodological rigor in these papers. Here, we present the potential and limitations of these evolving evidence synthesis tools by looking at umbrella reviews published on vaccine research. Vaccines are essential tools in modern medicine for preventing disease and promoting public health. The scientific literature on vaccines grows rapidly as researchers work to improve existing vaccines and develop new ones. More than half a million scientific papers on vaccines have already been published, including several thousands of systematic reviews that aim to appraise and summarize this growing literature. However, as the published systematic reviews are only able to cover a small proportion of the literature it is important to also provide higher-level evidence syntheses. and discuss further improvements that could be made to integrate evidence on vaccines.

Febrile seizures: A clinical review and focus on caregiver education

ABSTRACT

Febrile seizures are the most common seizure disorder in childhood. Most febrile seizures have a benign course and children have a good prognosis. However, febrile seizures are traumatizing events for a child's family or caregiver to witness. Appropriate caregiver education is crucial to ease anxiety. This article reviews the risk factors, clinical presentation, diagnostics, treatment, and prevention of febrile seizures in addition to providing a guideline for effective caregiver education and support.

An economic evaluation and incremental analysis of the cost effectiveness of three universal childhood varicella vaccination strategies for Ireland

BACKGROUND

The cost effectiveness of childhood varicella vaccination is uncertain, as evidenced by variation in national health policies. Within the European Economic Area (EEA), only 10 of 30 countries offer universally funded childhood varicella vaccination. This study estimates the cost effectiveness of universal childhood varicella vaccination for one EEA country (Ireland), highlighting the difference in cost effectiveness between alternative vaccination strategies.

METHODS

An age-structured dynamic transmission model, simulating varicella zoster virus transmission, was developed to analyse the impact of three vaccination strategies; one-dose at 12 months old, two-dose at 12 and 15 months old (short-interval), and two-dose at 12 months and five years old (long-interval). The analysis adopted an 80-year time horizon and considered payer and societal perspectives. Clinical effectiveness was based on cases of varicella and subsequently herpes zoster and post-herpetic neuralgia avoided, and outcomes were expressed in quality-adjusted life-years (QALYs). Costs were presented in 2022 Irish Euro and cost effectiveness was interpreted with reference to a willingness-to-pay threshold of €20,000 per QALY gained.

RESULTS

From the payer perspective, the incremental cost-effectiveness ratio (ICER) for a one-dose strategy, compared with no vaccination, was estimated at €8,712 per QALY gained. The ICER for the next least expensive strategy, two-dose long-interval, compared with one-dose, was estimated at €45,090 per QALY gained. From a societal perspective, all three strategies were cost-saving compared with no vaccination; the two-dose short-interval strategy dominated, yielding the largest cost savings and health benefits. Results were stable across a range of sensitivity and scenario analyses.

CONCLUSION

A one-dose strategy was highly cost effective from the payer perspective, driven by a reduction in hospitalisations. Two-dose strategies were cost saving from the societal perspective. These results should be considered alongside other factors such as acceptability of a new vaccine within the overall childhood immunisation schedule, programme objectives and budget impact.

Adverse events following immunisation: Prospective cohort study evaluating Australian children presenting to specialist immunisation clinics

OBJECTIVE

Prior experience of an adverse event following immunisation is a known barrier to vaccination. Limited Australian data evaluating adverse event recurrence among children exists to inform clinical decisions. We aimed to assess adverse event following immunisation recurrence among children with prior adverse events and to evaluate if family history increased adverse event risk.

METHODS

A prospective cohort study was conducted from March 3rd until August 18th, 2023. Children ≤ 16 years with prior adverse events following immunisation in themselves or family were recruited from specialist immunisation clinics at two quaternary paediatric hospitals. Adverse event outcomes were collected via surveys administered at presentation, three, and eight days post vaccination, and analysed by key characteristics and potential risk factors.

RESULTS

Forty three of forty nine (43/49, 87.8 %) children enrolled received further vaccines. Of those who completed the follow up surveys, 50.0 % (16/32) reported an adverse event. Recurrence of prior adverse events occurred for 23.3 % (10/43, 95 % CI: 11.8 % - 38.6 %) of the cohort. Two of twelve (2/12, 16.7 %) participants with prior serious adverse events who received further vaccines reported a serious adverse event recurrence. No post review serious adverse events were observed in children with prior non serious adverse events. Neurological conditions were a risk factor for prior (neurological condition 3/3 versus no neurological condition 2/40, p < 0.001) and post review (neurological condition 2/3 versus no neurological condition 0/28, p = 0.006) post vaccination seizures. Family history had no relationship to post review adverse events (family history 5/8 versus no family history 11/23, p = 0.685).

CONCLUSION

Revaccination is safe for the majority of children with a personal or family history of adverse event following immunisation.

Do vaccines cause epilepsy? Review of cases in the National Vaccine Injury Compensation Program

OBJECTIVE

The National Childhood Vaccine Injury Act of 1986 created the National Vaccine Injury Compensation Program (VICP), a no-fault alternative to the traditional tort system. Since 1988, the total compensation paid exceeds $5 billion. Although epilepsy is one of the leading reasons for filing a claim, there has been no review of the process and validity of the legal outcomes given current medical information. The objectives were to review the evolution of the VICP program in regard to vaccine-related epilepsy and assess the rationale behind decisions made by the court.

METHODS

Publicly available cases involving epilepsy claims in the VICP were searched through Westlaw and the US Court of Federal Claims websites. All published reports were reviewed for petitioner's theories supporting vaccine-induced epilepsy, respondent's counterarguments, the final decision regarding compensation, and the rationale underlying these decisions. The primary goal was to determine which factors went into decisions regarding whether vaccines caused epilepsy.

RESULTS

Since the first epilepsy case in 1989, there have been many changes in the program, including the removal of residual seizure disorder as a vaccine-related injury, publication of the Althen prongs, release of the acellular form of pertussis, and recognition that in genetic conditions the underlying genetic abnormality rather than the immunization causes epilepsy. We identified 532 unique cases with epilepsy: 105 with infantile spasms and 427 with epilepsy without infantile spasms. The petitioners' experts often espoused outdated, erroneous causation theories that lacked an acceptable medical or scientific foundation and were frequently criticized by the court.

SIGNIFICANCE

Despite the lack of epidemiological or mechanistic evidence indicating that childhood vaccines covered by the VICP result in or aggravate epilepsy, these cases continue to be adjudicated. After 35 years of intense litigation, it is time to reconsider whether epilepsy should continue to be a compensable vaccine-induced injury.

Combined measles-mumps-rubella-varicella vaccine and febrile convulsions: the risk considered in the broad context

INTRODUCTION

Studies on quadrivalent measles, mumps, rubella, and varicella (MMRV) vaccines have indicated a twofold increased relative risk of febrile convulsion (FC) after the first dose compared to MMR and V administered at the same medical visit (MMR+V).

AREAS COVERED

This narrative review contextualizes FC occurrence after the first MMRV vaccine dose from a clinical perspective and outlines approaches to attenuate FC occurrence post-vaccination.

EXPERT OPINION

While the relative FC risk increases after the first dose of MMRV compared to MMR+V vaccine in measles-naïve infants, the attributable risk is low versus the overall FC risk in the pediatric population triggered by other causes, like natural exposure to pathogens or routine vaccination. No increased risk of FC has been reported after MMRV co-administration with other routine vaccines compared to MMRV alone. Based on our findings and considering the MMRV vaccination benefits (fewer injections, higher coverage, better vaccination compliance), the overall benefit-risk profile of MMRV vaccine is considered to remain positive. Potential occurrence of FC in predisposed children (e.g. with personal/family history of FC) may be attenuated if they receive MMR+V instead of MMRV as the first dose. It is also important to monitor vaccinees for fever during the first 2 weeks post-vaccination.