Varicella: a vaccine preventable disease?

Management of chickenpox in pregnant women: an Italian perspective

Chickenpox is a highly contagious disease caused by primary infection of varicella zoster virus (VZV). The disease is spread worldwide and is usually benign but, in some groups of population like pregnant women, can have a severe outcome. Due to a not optimal vaccination coverage, a relatively high number of childbearing-aged women in a European country such as Italy tested seronegative for VZV and so are currently at risk of acquiring chickenpox during pregnancy, especially if they live in contact with children for family or work reasons. Only few data are available about the risk of infection in this setting: the incidence of chickenpox may range from 1.5 to 4.6 cases/1000 childbearing females and from 1.21 to 6 cases/10,000 pregnant women, respectively. This review is aimed to focus on the epidemiology and the clinical management of exposure to chickenpox during pregnancy. Particular emphasis is given to the accurate screening of childbearing women at the time of the first gynecological approach - the females who tested susceptible to infection can be counseled about the risks and instructed on procedure should contact occur - and to the early prophylaxis of the at-risk exposure. Lastly, the achievement of adequate vaccination coverage of the Italian population remains a cornerstone in the prevention of chickenpox in pregnancy.

Varicella-zoster vaccine in the USA: success for control of disease severity, but what next?

In the period from 1990 to 1994, before the introduction of a varicella vaccine to the USA, approximately 100 deaths in otherwise healthy individuals, children and adolescents under 20 years of age, were attributable to varicella complications. The administration of a single-dose vaccine has now been widespread in the USA for nearly 10 years; however, since the effectiveness of a single dose in children under 13 years of age in an outbreak situation is approximately 80%, consideration of a second booster dose is in progress although not yet recommended. Licensure of a measles-mumps-rubella-varicella vaccine may hasten the recommendation.

The incidence of varicella and herpes zoster in Taiwan during a period of increasing varicella vaccine coverage, 2000-2008

The introduction and the widespread use of the varicella vaccine in Taiwan has led to a 75-80% decrease in the incidence of varicella in children. However the vaccine's long-term impact on the incidence of herpes zoster (HZ) has attracted attention. By controlling gender, underlying diseases, and age effects, a Poisson regression was applied on the 2000-2008 chart records of 240 000 randomly selected residents who enrolled in the Universal National Health Insurance. The results show that, as the vaccine coverage in children increases, the incidence of varicella decreases. However, the incidence of HZ increased even before the implementation of the free varicella vaccination programme in 2004, particularly in females. The increase in the incidence of HZ cannot be entirely and directly attributed to the widespread vaccination of children. Continuous monitoring is needed to understand the secular trends in HZ before and after varicella vaccination in Taiwan and in other countries.

Varicella-zoster virus (chickenpox) infection in pregnancy

Congenital varicella syndrome, maternal varicella-zoster virus pneumonia and neonatal varicella infection are associated with serious fetomaternal morbidity and, not infrequently, mortality. Vaccination against varicella-zoster virus can prevent the disease, and outbreak control limits the exposure of pregnant women to the infectious agent. Maternal varicella-zoster immunoglobulin administration before rash development, with or without antiviral medication, can modify the progression of the disease.

A new challenge for Europe: introducing a pediatric quadrivalent vaccine for measles, mumps, rubella, and varicella

BACKGROUND

Varicella is often considered to be a benign disease of childhood. In fact, varicella is associated with serious complications and mortality even among healthy individuals.

DISCUSSION

Although the course of varicella can be uncomplicated, it can also be associated with serious complications such as pneumonia, fluid and electrolyte disturbances, skin and soft tissue infections and central nervous system disturbances. Worldwide studies have confirmed the high frequency of disease as well as the resultant morbidity, mortality and medical resource use. A quadrivalent vaccine is now available in certain countries to protect against measles, mumps, rubella and varicella (MMRV). Countries that have initiated routine vaccination pro- grams have reported substantial reductions in morbidity and mortality as well as improved health outcomes. The MMRV vaccine facilitates coverage against all four diseases, and would be expected to improve compliance as well as coverage of varicella.

CONCLUSIONS

Universal vaccination programs with MMRV should be considered as a way to reduce the medical and economic impact of varicella. The MMRV vaccine provides a means to achieve universal coverage.

Herpes simplex and varicella-zoster virus infections during pregnancy: current concepts of prevention, diagnosis and therapy. Part 2: Varicella-zoster virus infections

Varicella during pregnancy can be associated with severe illnesses for both the mother and her neonate. Varicella pneumonia must be regarded as a medical emergency, since pregnant women are at risk of life-threatening ventilatory compromise and death. After maternal chickenpox in the first and second trimesters, congenital varicella syndrome may occur in nearly 2% of the cases. The characteristic symptoms consist of skin lesions in dermatomal distribution, neurological defects, eye diseases and skeletal anomalies. If the mother develops varicella rashes between day 4 (5) antepartum and day 2 postpartum, generalized neonatal varicella leading to death in about 20% of the cases has to be expected. Normal zoster has not been shown to be associated with maternal pneumonia, birth defects or problems in the perinatal period. On the basis of the clinical consequences of varicella-zoster virus infections during pregnancy, the present paper summarizes the currently available concepts of prevention, diagnosis and therapy.

Safety, tolerability, and immunogenicity of a two-dose regimen of high-titer varicella vaccine in subjects ≥13 years of age

A new manufacturing process, known as process upgrade varicella vaccine (PUVV) was developed for a refrigerated formulation of varicella vaccine and for an investigational zoster vaccine. Safety and tolerability of a two-dose regimen of high-titered (approximately 50,000 PFU) PUVV were compared to a lower-titer formulation (approximately 5400 PFU) of VARIVAX; in 1366 healthy subjects > or =13 years old. Only one vaccine-related clinical serious adverse experience (pruritus; no hospitalization) was reported, in the VARIVAX group. Injection-site adverse experiences following any dose were higher in the PUVV group, 70.0%, than in the VARIVAX group, 56.2%, but generally were mild. Immunogenicity were similar in both groups in seronegative subjects. PUVV was generally well tolerated, and elicited an immune response similar to that induced by the marketed formulation of VARIVAX.

Genotyping of different varicella vaccine strains

BACKGROUND

Little is known about single nucleotide polymorphism (SNP) in different lots of varicella vaccines distributed by the manufacturers. Recently, the genetic analysis of several genomic regions revealed a polymorphism in different vaccine lots of Varilrix manufactured by GlaxoSmithKline. These findings need attention since mutations in the vaccine strain could result in changes of virulence and efficacy of the vaccine.

OBJECTIVES

To identify SNPs in three varicella vaccine lots of Varilrix and to compare the results with that of Varivax as well as the published sequences of the Oka vaccine strain (V-Oka) and its parental virus (P-Oka).

STUDY DESIGN

The open reading frames (ORF) 1, 6, 10, 21, 50, 54, and 62 were analyzed by sequencing of amplified DNA fragments.

RESULTS

Wild-type nucleotides identical to that of P-Oka and/or the European wild-type reference strain Dumas and in contrast to V-Oka could be identified in ORF 1 of a Varilrix vaccine lot distributed in 1991. In the ORF 62 probably responsible for attenuation of V-Oka, this vaccine strain contained 16 SNPs which were nearly all wild-type-like. By contrast, different lots of the Varivax vaccine revealed uniform sequencing results. The vaccine Varilrix 1999 showed a high similarity to the Varivax vaccine currently available.

CONCLUSIONS

The obvious genetic diversity of different lots of the varicella vaccine Varilrix cannot be explained with the coexistence of several strain variants in the vaccine, but most likely with different seed lot preparations used for vaccine production.