Committee on Infectious Diseases. Policy statement—Prevention of varicella: update of recommendations for use of quadrivalent and monovalent varicella vaccines in children

Issues in pediatric vaccine-preventable diseases in low- to middle-income countries

The highest burden of pediatric vaccine-preventable disease is found in developing nations where resource constraints pose the greatest challenge, impacting disease diagnosis and surveillance as well as the implementation of large scale vaccination programmes. In November 2012, a Working Group Meeting convened in Casablanca to describe and discuss the status with respect to 8 vaccine-preventable diseases (pertussis, pneumococcal disease, measles-mumps-rubella-varicella (MMRV), rotavirus and meningococcal meningitis) to identify and consider ways of overcoming obstacles to pediatric vaccine implementation. Experts from Europe, Russia, the Commonwealth of Independent States, the Middle East, Africa and South East Asia participated in the meeting. A range of region-specific needs and barriers to uptake were discussed. The aim of this article is to provide a summary of the ongoing status with respect to pediatric vaccine preventable disease in the countries represented, and the experts' opinions and recommendations with respect to pediatric vaccine implementation.

A double blind, randomized, active controlled study to assess the safety, tolerability and immunogenicity of measles, mumps rubella, and varicella vaccine (MMRV) manufactured using an alternative process

Vaccination against measles, mumps, rubella, and varicella is recommended for all children in the US. Limitations manufacturing Oka/Merck strain varicella-zoster virus have hampered the availability of the combination vaccine (MMRV) against these 4 viruses, which drove the need to investigate an alternative manufacturing process. Healthy children 12-to-23 months of age at 71 US sites were randomized (1:1) to receive MMRV manufactured using an alternative process (MMRVAMP) or the currently licensed MMRV. Subjects received 2 0.5 mL doses 3 months apart. Sera were collected before and 6 weeks after Dose-1. Adverse experiences (AEs) were collected for 42 d after each dose and serious AEs and events of special interest for 180 d after Dose-2. Overall, 706 subjects were randomized to MMRVAMP and 706 to MMRV and 698 and 702 received at least 1 dose of study vaccine, respectively. The risk difference in response rates and geometric mean concentrations of antibody to measles, mumps, rubella, and varicella viruses 6 weeks after Dose-1 met non-inferiority criteria for MMRVAMP versus, MMRV. Response rates met acceptability criteria for each virus, and the seroconversion rate to varicella-zoster virus was 99.5% in both groups. Vaccine-related AEs were mostly mild-to-moderate in intensity and somewhat more common after MMRVAMP. Febrile seizures occurred at similar rates in both groups during the first 42 d after each vaccine dose. MMRVAMP is non-inferior to MMRV and represents an important advancement in maintaining an adequate supply of vaccines against these diseases.

Clinical and molecular aspects of the live attenuated Oka varicella vaccine

VZV is a ubiquitous member of the Herpesviridae family that causes varicella (chicken pox) and herpes zoster (shingles). Both manifestations can cause great morbidity and mortality and are therefore of significant economic burden. The introduction of varicella vaccination as part of childhood immunization programs has resulted in a remarkable decline in varicella incidence, and associated hospitalizations and deaths, particularly in the USA. The vaccine preparation, vOka, is a live attenuated virus produced by serial passage of a wild-type clinical isolate termed pOka in human and guinea pig cell lines. Although vOka is clinically attenuated, it can cause mild varicella, establish latency, and reactivate to cause herpes zoster. Sequence analysis has shown that vOka differs from pOka by at least 42 loci; however, not all genomes possess the novel vOka change at all positions, creating a heterogeneous population of genetically distinct haplotypes. This, together with the extreme cell-associated nature of VZV replication in cell culture and the lack of an animal model, in which the complete VZV life cycle can be replicated, has limited studies into the molecular basis for vOka attenuation. Comparative studies of vOka with pOka replication in T cells, dorsal root ganglia, and skin indicate that attenuation likely involves multiple mutations within ORF 62 and several other genes. This article presents an overview of the clinical aspects of the vaccine and current progress on understanding the molecular mechanisms that account for the clinical phenotype of reduced virulence.

Immunogenicity and safety of a tetravalent measles-mumps-rubella-varicella vaccine: an open-labeled, randomized trial in healthy Korean children

Purpose

This study (NCT00751348) evaluated the immunogenicity and safety of a combined measles-mumps-rubella-varicella (MMRV) vaccine compared to co-administration of measles-mumps-rubella and varicella (MMR+V) vaccines in Korean children during their second year of life.

Materials and Methods

Healthy children aged 11-24 months received one dose of MMRV or MMR+V. Antibody titers against measles, mumps and rubella were measured using enzyme-linked immunosorbent assay and against varicella using an immunofluorescence assay. Parents/guardians recorded adverse events in diary cards for up to 43 days post-vaccination. The primary objective was to demonstrate non-inferiority of MMRV to MMR+V for all antigens in terms of seroconversion rates (SCRs), defined as a group difference with a lower limit of the 95% confidence interval (CI)>-10%.

Results

Of 474 subjects enrolled, 458 (MMRV, 301; MMR+V, 157) were included in the according-to-protocol cohort. For measles (98.0% vs. 99.4%), rubella (99.7% vs. 100%) and varicella (98.9% vs. 100%) SCRs, the lower limits of the 95% CIs for group differences were greater than -10%; however, for mumps SCRs (88.8% vs. 94.2%), it was -10.40%. The primary objective of non-inferiority in mumps SCRs was therefore not met, although the observed group difference in a post-hoc analysis of anti-mumps antibodies using a plaque reduction neutralization assay was 0.39% with a 95% CI lower limit of -4.03%. Adverse events occurred at comparable frequencies for both groups, except for more frequent fever in MMRV recipients.

Conclusion

Based on the pre-specified non-inferiority criterion, SCRs of the MMRV vaccine were non-inferior to that elicited by MMR+V vaccines for all antigens except mumps.

Epilepsy and vaccinations: Italian guidelines

Reports of childhood epilepsies in temporal association with vaccination have had a great impact on the acceptance of vaccination programs by health care providers, but little is known about this possible temporal association and about the types of seizures following vaccinations. For these reasons the Italian League Against Epilepsy (LICE), in collaboration with other Italian scientific societies, has decided to generate Guidelines on Vaccinations and Epilepsy. The aim of Guidelines on Vaccinations and Epilepsy is to present recent unequivocal evidence from published reports on the possible relationship between vaccines and epilepsy in order to provide information about contraindications and risks of vaccinations in patients with epilepsy. The following main issues have been addressed: (1) whether contraindications to vaccinations exist in patients with febrile convulsions, epilepsy, and/or epileptic encephalopathies; and (2) whether any vaccinations can cause febrile seizures, epilepsy, and/or epileptic encephalopathies. Diphtheria-tetanus-pertussis (DTP) vaccination and measles, mumps, and rubella vaccination (MMR) increase significantly the risk of febrile seizures. Recent observations and data about the relationships between vaccination and epileptic encephalopathy show that some cases of apparent vaccine-induced encephalopathy could in fact be caused by an inherent genetic defect with no causal relationship with vaccination.

Economic evaluation of Varicella vaccination: results of a systematic review

INTRODUCTION

The aim of the present study is to review the economic burden of varicella disease and the benefit of universal varicella vaccination in different settings pending its implementation in all Italian regions.

MATERIALS AND METHODS

Research was conducted using PubMed, Scopus and ISI databases. Score quality and data extraction were performed for all included studies.

RESULTS

Twenty-three articles met the criteria: 15 cost-effectiveness, 8 cost-benefit and one cost-utility analysis. Varicella vaccination could save the society from €637,762 (infant strategy) to 53 million annually (combined infant and adolescent strategy). The median and the mean quality scores resulted in 91.8% and 85.4% respectively; 11 studies were considered of high quality and 12 of low quality.

DISCUSSION

The studies are favorable to the introduction of universal varicella vaccination in Italy, being cost saving and having a positive impact on morbidity. The quality score of the studies varied greatly: recent analyses were of comparable quality to older studies.

Immunogenicity and safety of combined measles-mumps-rubella-varicella vaccine using new measles and rubella working seeds in healthy children in Taiwan and Singapore: a phase II, randomized, double-blind trial

AIM

This study evaluated the immunogenicity and safety of tetravalent measles-mumps-rubella-varicella (MMRV) vaccine produced with measles and rubella monovalent bulks derived from a newly established working seed virus stock (MMRV(new WS)) compared with the combined MMRV vaccine derived from the current seed virus stock, in Taiwanese and Singaporean children (NCT00892775).

METHODS

Healthy children aged 11-22 mo were randomized to receive two doses of either the MMRV(new WS) vaccine or the MMRV vaccine. Antibody titers against measles, mumps and rubella were measured using ELISA and against varicella using an immunofluorescence assay. The primary objective was to demonstrate non-inferiority of MMRV(new WS) to MMRV in terms of post-dose-1 seroconversion rates, defined as a group difference with a lower limit of the 95% confidence interval greater than -10% for each antigen. Parents/guardians recorded symptoms in diary cards for 43 d after each vaccine dose.

RESULTS

Non-inferiority of MMRV(new WS) to MMRV was achieved for all vaccine antigens. The lower limits of the 95% confidence intervals for group differences (MMRV(new WS) group vs. MMRV) for measles (99.4% vs 100%), mumps (89.7% vs 90.4%), rubella (99.7% vs 100%) and varicella (97.6% vs 92.9%) seroconversion rates were greater than -10%. Mild symptoms including a peak in fever between days 5 and 12, post-dose-1, was observed in both groups.

CONCLUSION

The immune responses elicited by the MMRV(new WS) vaccine were non-inferior to that elicited by the MMRV vaccine for all antigens. Both vaccines exhibited an acceptable safety profile in Taiwanese and Singaporean children.

Immunogenicity and safety of two tetravalent (measles, mumps, rubella, varicella) vaccines coadministered with hepatitis a and pneumococcal conjugate vaccines to children twelve to fourteen months of age

BACKGROUND

This study compared single-dose tetravalent measles, mumps, rubella, varicella vaccine, Priorix-Tetra, stored refrigerated (GSK+4C) or frozen (GSK-20C), with ProQuad (Merck-20C), when coadministered with hepatitis A vaccine (HAV) and 7-valent pneumococcal conjugate vaccine (PCV7).

METHODS

Multicenter, observer-blind phase 2 study in 1783 healthy 12-14 month olds randomized to: GSK+4C (n = 705), GSK-20C (n = 689) or Merck-20C (n = 389), administered concomitantly with HAV (Havrix) and PCV7 (Prevnar). Seroresponse rates and antibody geometric mean concentrations/titers were determined from enzyme-linked immunosorbent assay and neutralization assays. Reactogenicity and safety were assessed.

RESULTS

Seroresponse rates (day 42) were >97% for measles and rubella viruses and >92% for mumps virus, in all groups. Noninferiority of both GSK+4C and GSK-20C vaccines versus Merck-20C was demonstrated for seroresponse rates to measles, mumps and rubella viruses (lower 97.5% confidence interval above -5%, -10% and -5%, respectively). For varicella-zoster virus, seroresponse rates were 57.1%, 69.8% and 86.7% in the GSK+4C, GSK-20C and Merck-20C groups, respectively. Noninferiority was not shown for either GSK vaccine (lower 97.5% confidence intervals <-15%). Geometric mean concentration ratios for anti-varicella-zoster virus demonstrated noninferiority (lower 97.5% confidence interval ≥ 0.5) versus Merck-20C for GSK-20C only. Geometric mean concentration ratios for antibodies to HAV and to PCV7 pneumococcal serotypes also met criteria for noninferiority for both GSK groups compared with Merck-20C. GSK vaccine safety was observed comparable to Merck-20C. Localized but not generalized measles/rubella-like rash and grade 3 fever was reported slightly more frequently with GSK vaccines, but antipyretic use was similar. The incidence of subjects experiencing at least 1 serious adverse event was 2.0%, 2.9% and 1.8% in the GSK+4C, GSK-20C and Merck-20C groups, respectively.

CONCLUSIONS

Noninferiority of both GSK measles, mumps, rubella, varicella vaccines versus Merck-20C was demonstrated for responses to measles, mumps and rubella viruses but was not fully demonstrated for varicella-zoster virus. The vaccines showed acceptable reactogenicity/safety when coadministered with HAV and PCV7.

Update on child and adolescent immunizations: selected review of US recommendations and literature

PURPOSE OF REVIEW

To provide a clinically relevant synopsis of recent research findings as well as updated guidelines from the American Academy of Pediatrics and Advisory Committee on Immunization Practices regarding child and adolescent immunizations.

RECENT FINDINGS

Childhood vaccinations have served to dramatically reduce pediatric morbidity and mortality in the USA. Much of the recent research has focused on the improvement of current vaccines as well as on the development of new vaccines. By improving the safety, efficacy and immunogenicity of vaccinations, children can be more fully protected. Additionally, recommendations have broadened as vaccinations have been proven well tolerated and effective for a growing number of subpopulations. Although more groups of children are now included in vaccination recommendations, efforts must continue to ensure that all eligible children receive their vaccinations. This article reviews selected recent publications on influenza, human papillomavirus, the childhood and adolescent/adult formulations of diphtheria and tetanus toxoids and acellular pertussis, meningococcal conjugate and pneumococcal vaccines. The relationship between febrile seizures and childhood immunizations is explored.

SUMMARY

The research on childhood and adolescent vaccinations is continuously growing and will serve to shape future recommendations. Through their findings, we can learn how to optimize the protection of all children and adolescents against these very serious diseases.