[Varicella vaccine]

Varicella and herpes zoster represent a significant public health problem. Safe and highly effective varicella vaccines against severe and moderate varicella are currently available. Vaccine efficacy is lower and more variable against mild disease and several risk factors have been associated with mild breakthrough disease. Experts are currently discussing the need for a second vaccine dose. Universal varicella vaccination has been highly effective in reducing morbidity and hospitalizations due to varicella, a strategy that has proven to be cost effective in many regions when the societal-perspective is considered in the analysis. Recent data suggests that varicella vaccination may be associated with an increased incidence of herpes zoster in the elderly. Immunity conferred by varicella vaccination seems to be longlasting but a continued evaluation is needed in order to asses the effect of the changing epidemiology associated with universal immunization.

[Clinical trials of oral recombinant bivaccine against variola and hepatitis B during double vaccination]

Clinical trials of oral live recombinant embryonic variola and hepatitis B bivaccine as tablets (Revax-BT) were performed. When volunteers were prevaccinated with oral variola vaccine first in a small dose and, 7, 14, 30, 90, and 180 days later, in a larger dose, a slight reactoginicity was sometimes observed after the first vaccination (with a small dose) whereas revaccination with a larger dose did not give rise to any clinical manifestations. A month after vaccination, a protective level of virus-neutralizing antibodies to vaccinia virus (VV) was observed in 90-100% of the volunteers twice immunized with the bivaccine (in a small dose and in a larger one at an administration intervals of 1-2 weeks under remote revaccination while 6-9 months following vaccination, this level was recorded in 80% of the volunteers. A month following vaccination, 50-55% seroconversion to VV was observed in the volunteers twice immunized with the bivaccine (at an interval of 1 or 3-6 months). Cellular immunity to VV was low (0-20%). Double immunization of volunteers with the oral bivaccine under remote vaccination failed to produce the significant levels of humoral and cellular immune responses to hepatitis B markers. Recombinant VV was not recorded in any blood, saliva, and urine samples taken in the volunteers twice immunized with the bivaccine.

Increasing evidence of immunity to varicella among children in Massachusetts, 1999-2003

BACKGROUND

Experiences with vaccine-preventable diseases have demonstrated the success of school-entry requirements in increasing vaccination coverage and decreasing disease incidence. This study examines the effect of early implementation of daycare and school-entry requirements for varicella vaccination on recorded varicella immunity of preschool and school-aged children in Massachusetts.

METHODS

Immunization surveys were conducted in licensed child care centers and schools with kindergarten and/or 7th grades. Evidence of immunity to varicella was defined as having physician verified records of varicella vaccination or disease history from the 1999-2000 through 2003-2004 school years.

RESULTS

During the 5-year study period, physician-certified reliable history of varicella disease decreased in each grade level while vaccination coverage increased. The increase in the number of children in each grade level receiving varicella vaccine led to an increase in the overall percentage of children with evidence of immunity to varicella: 85% to 97% for children aged 2 years or more in child care, 93% to 98% for children in kindergarten, and 88% to 92% for children in 7th grade.

CONCLUSIONS

The implementation of daycare and school-entry requirements for varicella vaccination within 4 years of the start of the varicella vaccination program in Massachusetts was associated with high levels of vaccination coverage in the cohorts of children targeted by the requirements. Although evidence of immunity from varicella disease decreased during the study period, the increase in varicella vaccination coverage compensated for the decline in disease history, resulting in a higher proportion of young children with evidence of immunity to varicella.

The cost-effectiveness of antenatal varicella screening with post-partum vaccination of susceptibles

Varicella infection during pregnancy or around the time of birth can result in serious complications for the mother and/or her child. However, infection during pregnancy is relatively rare as most women are infected during childhood. Immigrant mothers from certain tropical countries are at increased risk of infection, as these countries appear to have lower rates of infection during childhood. We used a cohort model to assess the potential costs and benefits of screening first-time pregnant mothers and then vaccinating those who are susceptible. The model was stratified by age and country of birth (Bangladesh or UK). The strategies evaluated were: (a) an initial verbal screen followed by a serological screen for those with a negative or uncertain history; (b) universal serological screening; and (c) the current strategy which is to treat cases as they arise. Post-partum vaccination was given to those who screen negative for VZV antibodies. The model suggested that the screening and vaccination strategies prevent cases in women compared with the current strategy. Verbal followed by serological screening may be cost-saving to the NHS for both UK- and Bangladesh-born women. Universal screening is more costly but more effective than verbal screening, and it may be cost-effective to universally screen younger immigrant mothers.

Varicella-zoster virus vaccine: A review of its use in the prevention of herpes zoster in older adults

Current strategies for managing herpes zoster show variable efficacy and do not prevent its appearance. Varicella-zoster virus vaccine, or "zoster vaccine" is a more potent form of the varicella-zoster virus vaccine currently approved for use in the prevention of varicella in children. Zoster vaccine decreases the incidence of herpes zoster and burden of illness in adults aged 60 years and older and appears more efficacious in patients aged 60-69 than in those over 70 years. Importantly, the incidence of postherpetic neuralgia is significantly reduced in patients who receive zoster vaccine, irrespective of age or sex. The duration of postherpetic neuralgia is also significantly reduced. Zoster vaccine has a favorable safety profile; most treatment-related adverse events are related to the site of injection. This review summarizes the current data on the clinical efficacy and safety of zoster vaccine in adults aged 60 years and older.

Cost-Effectiveness Analysis of Routine Immunization for Varicella in Japan

OBJECTIVE

Immunization for varicella is not currently included in routine immunizations in Japan. This study was conducted to assess test its cost-effectiveness when it becomes a routine.

METHODS

We surveyed and collected information for the year beginning 15th June 2004 in one area. Almost all 11 pediatric clinics or hospitals in the area cooperated in this survey. There was a questionnaire form for families and for doctors. Absent days from routine tasks, i.e., job, housekeeping or study, for family nursing and others were asked on family form. Medical costs and other costs were asked on doctor form. Neither form included the patient's name or name of the medical institution. Doctors explained this survey to patients' family on their first visiting day and asked to cooperate. If they refused the doctor form was also discarded. Since family form was written after recovery and mailed, cooperation in this survey was voluntary. Opportunity cost for family nursing is estimated as opportunity cost based on the 2002 Basic Surveillance of Wage Structure. The burden of sequel cases was estimated assuming six million yen per Quality-adjusted Life Years (QALY). Total number of patients was estimated to be 0.84 million, which includes unvaccinated people in a birth cohort. We adopted incremental benefit cost ratios form societal viewpoint as a measure.

RESULTS

We collected 402 data from the doctor form and 265 from the family form. Total disease burden in all of Japan is estimated to be 52.2 billion yen, but opportunity cost accounted for 80%. The incremental benefit cost rations averaged more than 4 when vaccination cost is assumed to be five to twelve thousand yen. The lower limit of the confidence intervals is about 1.5.

DISCUSSION AND CONCLUSION

The disease burden of varicella was greater than measles in 2000, when there were measles 0.2 million patients. The incremental benefit cost ratio showed that there will almost surely be an additional benefit due to routine immunization is greater than the additional cost. Therefore, we found strong evidence for routine immunization for varicella.

Immunogenicity and safety of two doses of tetravalent measles-mumps-rubella-varicella vaccine in healthy children

BACKGROUND

Combination vaccines against common childhood diseases are widely used, provide an improved coverage, are more convenient and are more cost-effective than multiple injections. We conducted a study to evaluate the safety and immunogenicity of a combined measles-mumps-rubella-varicella (MMRV) candidate vaccine in comparison with the separate administration of licensed measles-mumps-rubella (MMR; Priorix) and varicella (V; Varilrix) vaccines.

METHODS

Healthy children 12-18 months of age received 2 doses of MMRV vaccine (3 lots) 6-8 weeks apart (MMRV group) or 1 dose of MMR vaccine administered concomitantly with 1 dose of varicella vaccine, followed by a second dose of MMR at 6-8 weeks later (MMR+V group). Local symptoms (redness, pain and swelling) were recorded for 4 days after vaccination, and fever (any, axillary temperature > or =37.5 degrees C or rectal temperature > or =38.0 degrees C; grade 3, axillary temperature >39.0 degrees C or rectal temperature >39.5 degrees C) was monitored daily for 15 days. Other adverse events were monitored for 6 weeks.

RESULTS

A total of 494 children were vaccinated (371 in the MMRV group and 123 in the MMR+V group. Two doses of MMRV vaccine were at least as immunogenic as 2 doses of MMR and 1 dose of varicella vaccine. After the second dose, all children had seroconverted to measles, rubella and varicella in both vaccine groups, and 98% versus 99% had seroconverted to mumps in the MMRV versus the MMR+V group, respectively. The MMRV vaccine did not induce an increased local or general reactogenicity compared with the separate administration, although a higher incidence of low grade fever was seen after the first dose in the MMRV group (67.7% after MMRV versus 48.8% after MMR+V; P < 0.05), this was not observed for grade 3 fever (11.6% after MMRV versus 10.6% after MMR+V; P = 0.87). After the second dose, no differences in incidence of fever were found in either MMRV or MMR+V groups.

CONCLUSION

Administration of 2 doses of the combined MMRV vaccine was as immunogenic and well-tolerated as separate injections of MMR and varicella vaccine.

Universal varicella vaccination: efficacy trends and effect on herpes zoster

In 1995, the Varicella Active Surveillance Project (VASP) was established in Antelope Valley (California), a geographically distinct high-desert community of 300,000 residents, as one of three sites in the nation in a cooperative agreement with the Centers for Disease Control and Prevention (CDC) to collect baseline demographic and clinical data and to monitor trends in varicella (chickenpox) following introduction of varicella vaccine. Herpes zoster (shingles) was added to the active surveillance January 1, 2000. The universal varicella program has proven effective in terms of reducing the number of reported verified varicella cases by 85%, from 2,934 in 1995 to 412 in 2002. Prior to this dramatic reduction, immunologic boosting due to exogenous exposures to wild-type varicella-zoster virus (VZV) in the community (1) caused mean serum anti-VZV levels among vaccines to increase with time after vaccination and (2) served as a mechanism that helped suppress the reactivation of herpes zoster (HZ), especially among individuals with a previous history of wild-type varicella. That immunologic boosting might play a significant role in both varicella and the closely related HZ epidemiology is evidenced by (1) a decline in vaccine efficacy by over 20%, from 95.7% (95% C.I., 82.7% to 98.9%) in 1999 to 73.9% (95% C.I., 57.9% to 83.8%) in 2001 and (2) an unexpectedly high cumulative (2000 to 2003) true incidence rate of 223 (95% C.I. 180-273) per 100,000 person-years (p-y) among children <10 years old with a previous history of varicella. Because capture-recapture methods demonstrate a likely lower bound of 50% underreporting, the actual rate is likely double or 446 per 100,000 p-y, approaching the HZ rate reported among older adults. Other recent studies based on VASP data have mitigated against discovery of the above trends that challenge several initial assumptions inherent to the universal varicella program, namely, (1) a single dose confers long-term immunity and (2) there is no immunologically mediated link between varicella and HZ incidence. As vaccinated children replace those with a prior history of wild-type varicella in the <10 age group, increasing HZ incidence among this cohort will be of less concern in the near future. However, previous scientific studies, including the present preliminary results from active surveillance indicate that HZ may be increasing among adults. It may be difficult to design booster interventions that are cost-effective and meet or exceed the level of protection provided by immunologic boosting that existed naturally in the community in the prelicensure era.

Herpes zoster ophthalmicus in an otherwise-healthy child

Herpes zoster ophthalmicus, although not uncommon in adults, is rarely found in children. Herein we present a case of pediatric herpes zoster ophthalmicus that is unique in 2 ways. First, the child had been vaccinated against varicella and otherwise had no known exposure to varicella-zoster virus. Second, the initial presentation of herpes zoster ophthalmicus was a painful and diffuse subconjunctival hemorrhage that appeared before any of its classic signs were observed. We report this case to document the possible occurrence of herpes zoster ophthalmicus in children who have been vaccinated against varicella and the possibility of a diffuse, painful subconjunctival hemorrhage as a presenting sign.

Determining the rate of varicella vaccine rash in children with moderate-severe eczema

OBJECTIVES

To determine the rate and severity of vesicular reactions following varicella vaccine in children with moderate-severe eczema. Secondary endpoints included the rates and severity of local reactions and eczema severity change within 42 days of vaccination.

METHODS

Prospective open intervention pilot study of varicella vaccine in children aged 12 months to 13 years with moderate-severe eczema. Children were given varicella vaccine alone and followed for 42 days after vaccination.

RESULTS

Fifty children, aged 12 months to 10.5 years were recruited, with complete follow-up for 48. A vesicular rash with a single lesion occurred in one child (2.1% (95% CI: 0, 11.1%)), 10 days following vaccination. Local reactions, including erythema, swelling and tenderness, were reported in eight children (16.7%). A flare-up of moderate-severe generalized eczema was reported in one child (2.1%) during the first week following varicella vaccine.

CONCLUSIONS

Vesicular rash and local reactions following varicella vaccination were no more common or severe in children with moderate-severe eczema than that reported in the published literature in children without eczema. Eczema in the 42 days following vaccination did not appear to increase in severity.

Varicella vaccination of children in the United States: assessment after the first decade 1995-2005

Live attenuated varicella vaccine (strain Oka) was approved for administration to healthy children in the United States in 1995. Over the past 10 years, varicella vaccine has been given to millions of children, usually at ages between 12 and 18 months. In states such as California, Michigan, and Texas, there has been a marked decline in the number of reported cases of varicella. Furthermore, there has been a 75% decrease in varicella-related hospitalizations across the United States, as well as a similar decrease in the number of deaths caused by complications of chickenpox. The main unanticipated result has been a growing number of outbreaks of varicella among immunized children ("breakthrough varicella"). The most cited risk factors for breakthrough varicella include the following: (1) 3-5-year interval since immunization and (2) immunization at the youngest ages, especially 12 months. Explanations for breakthrough varicella include a lessened immune response among the youngest recipients of the vaccine. Another possibility is genetic variation among circulating VZV strains. VZV strains can be separated into two geographic clades called European/North American and Asian, based on single nucleotide polymorphisms. Two mutant North American strains have been isolated from patients in the last 10 years. Several genomic differences between Oka vaccine strain and other strains have also been identified, including one site at the DNA origin of replication. Since breakthrough disease among vaccine recipients appears to be more common in the United States than in Japan, further comparisons between the varicella vaccination programs in Japan and the United States are warranted. In addition, data from varicella vaccination programs in Europe should provide further insight into the effectiveness of varicella vaccination in different geographic and ethnic populations.

Seroprevalence of varicella among children and adolescents in Valencia, Spain. Reliability of the parent's reported history and the medical file for identification of potential candidates for vaccination

This study assessed the seroprevalence of varicella antibodies in children and adolescents in Spain and evaluated the reliability of two methods for detecting susceptible individuals: (1) parental-reported history of varicella and (2) medically-documented histories maintained by the pediatrician. A total of 186 children (6 to 15 years of age) were recruited in 13 pediatric offices of Valencia, Spain. A brief case report form was completed including previous history of varicella referred by the parents, and a 5 mL blood sample was obtained. The pediatrician medical file was reviewed for antecedent of varicella. The overall prevalence of varicella antibodies was 84% and 88% in the 6-9 years and 10-15 years age brackets, respectively. The predictive value of a negative history of varicella disease was 48% by parental recall (52% "false negative"), and only 26% by medical record (74% "false negative"). However, the positive predictive value of a positive parental reported history or a positive medically-documented history was 95%. The most effective strategy for varicella vaccination of older children and adolescents in Spain will be to immunize those individuals with a lack of positive (unknown or negative) history of disease.

Dose-response study of a quadrivalent measles, mumps, rubella and varicella vaccine in healthy children

BACKGROUND

A combined measles, mumps, rubella and varicella (MMRV) vaccine would facilitate universal immunization against 4 diseases by decreasing the number of injections and thus enhancing compliance and coverage rates. If a second dose of varicella vaccine were to be recommended, MMRV could be used to administer a routine second dose of M-M-RII with the added advantage of boosting varicella-zoster virus (VZV) antibody titers.

METHODS

Subjects 12-23 months of age received a single injection of 1 of 3 lots of an MMRV vaccine (ProQuad) containing high, middle or low VZV potency, or VARIVAX given concomitantly with M-M-RII. Recipients of MMRV received a second injection of MMRV approximately 90 days later.

RESULTS

We enrolled 1559 subjects in the study. Antibody response rates to VZV 6 weeks after 1 injection of high potency MMRV (88.6%) or 2 injections of MMRV of any varicella potency (99.7-100%) were similar to the response rates after concomitant administration of M-M-RII and VARIVAX (93.1%). The second injection of MMRV boosted VZV antibody titers. Antibody responses to measles, mumps and rubella were >or=98%, similar to the control, after 1 or 2 injections of MMRV. MMRV was generally well-tolerated during the 42 days after vaccination.

CONCLUSIONS

One injection of high potency MMRV resulted in antibody responses to the 4 vaccine components equivalent to those found after concomitant administration of M-M-RII and VARIVAX. A second injection of MMRV resulted in a significant boost in VZV antibody. This boost may translate into enhanced immunogenicity against varicella, which is known to correlate with increased protection.

Evaluation of a quadrivalent measles, mumps, rubella and varicella vaccine in healthy children

BACKGROUND

A quadrivalent measles, mumps, rubella and varicella vaccine would facilitate universal immunization against all 4 diseases, improve compliance and immunization rates and decrease the number of injections given to children and visits to physicians' offices.

OBJECTIVES

To evaluate 1- and 2-dose regimens of a combined measles, mumps, rubella and varicella vaccine (ProQuad, referred to as MMRV) manufactured with a varicella component of increased potency.

METHODS

In this partially blind, multicenter study, 480 healthy 12- to 23-month-old children were randomized to receive either MMRV and placebo or M-M-RII and VARIVAX. Injections were given concomitantly at separate sites. Subjects randomized to receive MMRV and placebo received a second dose of MMRV 90 days later. Subjects were followed for 42 days after each vaccination for adverse experiences. Immunogenicity was evaluated 6 weeks after each vaccination.

RESULTS

Measles-like rash and fever during days 5-12 were more common after the first dose of MMRV (rash, 5.9%; fever, 27.7%) than after M-M-RII and VARIVAX (rash, 1.9%; fever, 18.7%). The incidence of other adverse events were similar between groups. Response rates were >90% to all vaccine components in both groups. Geometric mean titers to measles and mumps were significantly higher after 1 dose of MMRV than after administration of M-M-RII and VARIVAX. The second dose of MMRV elicited slight to moderate increases in measles, mumps and rubella antibody titers and a substantial increase in varicella antibody titer (from 13.0 to 588.1 glycoprotein antigen-based enzyme-linked immunosorbent assay units/mL).

CONCLUSION

A 1- or 2-dose regimen of MMRV is generally well-tolerated when administered to 12- to 23-month-old children and has a safety and immunogenicity profile similar to that of M-M-RII and VARIVAX administered concomitantly.

A mutant of Escherichia coli enterotoxin inducing a specific Thl-type of T cells to varicella-zoster vaccine enhances the production of IL-12 by IFNgamma-stimulated macrophages

A mutant of Escherichia coli enterotoxin induces specific Thl-type T cells to varicella-zoster vaccine. The mutant increased IL-12p40, TNFalpha and nitric oxide production by IFNgamma-stimulated bone marrow macrophages but cholera toxin did not. Anti-TNFalpha antibodies blocked its stimulation of IL-12p40 production but iNOS inhibitor did not. IL-12p40 and IL-12p35 production was stimulated at the level of mRNA formation by the mutant. Cholera toxin suppressed IL-12beta1 expression by spleen T cells stimulated with anti-CD3 antibodies but the mutant did not. These findings indicate that the mutant may induce Thl-type response to the vaccine through its IL-12 and TNFalpha induction by macrophages.

Seroepidemiology of varicella-zoster virus infection in a cosmopolitan city (Erzurum) in the eastern Turkey

OBJECTIVE

The aim of the study was to determine VZV seroprevalence under age 30 and to identify the relationship of VZV seroprevalence and several sociodemographic characteristics of the study subjects. The results were presented in order to design a strategy for vaccination against varicella-zoster virus (VZV).

MATERIAL AND METHOD

It was planned to include a total of 568 subjects. The sampling method of 30 clusters recommended for field studies was used for selecting subjects of a predetermined number in the rural and urban areas in eastern Turkey. ELISA method was used to examine the blood samples for VZV seropositivity. Age, gender, place of living, educational level, family size and socioeconomic status was investigated in the study subjects.

RESULTS

Positive VZV seroprevalence was detected in 78% of 559 subjects. Seroprevalence increased with age. Seroprevalence was 16.67% at the age of 1 year, subsequently increased to 57.58% at the age of 4 years, 70% at the age of 7 years, 92.31% at the age of 10 years and then remained 86.78-96.36% in subjects over the age of 10 years. No association was found between sociodemographic variables studied and prevalence levels of antibodies except for educational level in the 0-14 year group.

CONCLUSION

These results suggest that the majority of VZV infections occur during the early childhood; the best option to reduce the circulation of wild type VZV in the population would be the immunization of young children. VZV vaccine should be introduced into the routine childhood vaccination programme in Turkey.

The incidence of varicella and herpes zoster in Massachusetts as measured by the Behavioral Risk Factor Surveillance System (BRFSS) during a period of increasing varicella vaccine coverage, 1998-2003

BACKGROUND

The authors sought to monitor the impact of widespread varicella vaccination on the epidemiology of varicella and herpes zoster. While varicella incidence would be expected to decrease, mathematical models predict an initial increase in herpes zoster incidence if re-exposure to varicella protects against reactivation of the varicella zoster virus.

METHODS

In 1998-2003, as varicella vaccine uptake increased, incidence of varicella and herpes zoster in Massachusetts was monitored using the random-digit-dial Behavioral Risk Factor Surveillance System.

RESULTS

Between 1998 and 2003, varicella incidence declined from 16.5/1,000 to 3.5/1,000 (79%) overall with > or = 66% decreases for all age groups except adults (27% decrease). Age-standardized estimates of overall herpes zoster occurrence increased from 2.77/1,000 to 5.25/1,000 (90%) in the period 1999-2003, and the trend in both crude and adjusted rates was highly significant (p < 0.001). Annual age-specific rates were somewhat unstable, but all increased, and the trend was significant for the 25-44 year and 65+ year age groups.

CONCLUSION

As varicella vaccine coverage in children increased, the incidence of varicella decreased and the occurrence of herpes zoster increased. If the observed increase in herpes zoster incidence is real, widespread vaccination of children is only one of several possible explanations. Further studies are needed to understand secular trends in herpes zoster before and after use of varicella vaccine in the United States and other countries.

Barriers to adolescent immunization: a survey of family physicians and pediatricians

BACKGROUND

Although early childhood vaccination rates have increased, many adolescents are not up to date on recommended vaccinations. We assessed attitudes and practices of family physicians and pediatricians regarding adolescent vaccination to identify provider-level barriers that may contribute to low immunization rates.

METHODS

A 94-item self-report questionnaire was mailed to 400 physicians contracted with a managed care organization. Physicians were queried about demographic characteristics, source of vaccine recommendations, adolescent immunization practices, barriers to immunizing adolescents, and use of reminder/recall systems.

RESULTS

Response rate was 59%. Most respondents reported routinely recommending vaccines for tetanus and diphtheria toxoids (98%), Hepatitis B (90%), and measles, mumps, and rubella (84%), whereas 60% routinely recommended varicella vaccine. Physicians reported that they were more likely to assess immunization status, administer indicated immunizations, and schedule return immunization visits to younger adolescents (11 to 13 years old) than to older adolescents (14 to 18 and 19 to 21 years old).

CONCLUSION

Most respondents reported recommending the appropriate vaccinations during preventive health visits; however, older adolescents were least likely to be targeted for immunization assessment and administration of all recommended vaccines.

Chickenpox

PURPOSE OF REVIEW

Varicella-zoster virus (VZV) remains a public health issue around the globe despite the availability of a live attenuated vaccine and several highly active antiviral agents. A program of universal infant vaccination against varicella was introduced in the US almost 10 years ago. Epidemiological data continue to accumulate that will inform decision-making on vaccine use elsewhere. These findings, together with relevant advances in VZV virology, form the substance of this review.

RECENT FINDINGS

Understanding of the pathogenesis of varicella has significantly advanced with the demonstration that the cation-independent mannose 6-phosphate receptor is critical to both entry and egress of enveloped VZV. While our knowledge of intervening events remains sketchy, the future study of VZV will be facilitated by the recent successful cloning of the VZV genome into a bacterial artificial chromosome. Models of latency and reactivation are also being developed, which may help us to understand the epidemiology of herpes zoster in vaccinated populations. Continued evidence of decline in the incidence of varicella, associated hospitalizations and deaths suggests that the vaccine as used in the US is highly effective. However, rates of breakthrough disease are significant and sufficient to sustain outbreaks, even among highly vaccinated populations. This is so despite the generally reduced infectiousness of varicella occurring in vaccinated individuals. There is some evidence of attrition of the immune response over time following immunization in a small proportion of vaccinees.

SUMMARY

Our ability to prevent and treat varicella still outstrips our knowledge of pathogenetic and immune mechanisms. Further clinical advances are likely to arise from growing understanding of VZV biology.

Chickenpox vaccines: new drugs. A favourable risk-benefit balance in some situations

(1) Chickenpox is generally mild. Most severe cases of chickenpox occur in immunocompromised patients, adults, and pregnant women (and their foetuses). (2) Two live attenuated chickenpox vaccines derived from the same strain of varicella virus (Oka) are marketed in France, under the trade names Varilrix and Varivax. (3) They have not been adequately evaluated in immunocompromised children. (4) The impact of routine vaccination of women of child-bearing age on complications of chickenpox during pregnancy has not been studied. (5) Immunogenicity studies in several thousand immunocompetent children aged from 1 to 12 years show that the vaccine is almost always immunogenic after a single injection. Other comparative studies in adolescents and adults show that two injections are needed, at least two months apart. (6) A double-blind placebo-controlled trial including 513 immunocompetent children showed that Varilrix prevented 88% of cases of chickenpox after a median follow-up of 29 months, but no data on severe chickenpox were reported. A study that followed up 9202 children aged 1 to 12 years for more than 13 years showed that vaccination with Varivax failed to prevent chickenpox in 12.5% of cases and that 1.7% of these cases were severe. (7) Immunocompetent children vaccinated within three days after exposure to the virus are partially protected, according to one study of Varilrix (104 children) and two small studies of Varivax (10 and 42 children). There are no equivalent studies in adults. (8) Local adverse effects such as fever and rash are common in immunocompetent vaccinees. The rash is sometimes varicella-like and is due to infection by the vaccine strain. Pharmacovigilance studies of Varivax have shown no serious adverse effects. (9) Disseminated and/or persistent infection caused by the vaccine strain has been reported in immunocompromised patients. (10) Vaccination of immunocompetent subjects does not appear to result in a risk of chickenpox transmission to subsequent contacts. There seems to be no increase in the risk of herpes zoster in vaccinated children nor is there any firm evidence that chickenpox vaccination increases the incidence of herpes zoster in the general population. (11) Little information is available on vaccination during pregnancy. As a precaution, however, pregnant women should not be vaccinated. (12) Mass vaccination does not appear to be justified: chickenpox is generally mild during childhood, and several questions concerning the effects of the vaccine remain unanswered. (13) Chickenpox vaccination should be restricted to specific groups of non immune immunocompetent adults who are in a position to transmit chickenpox to immunodeficient contacts (e.g. health care personnel and kindergarten staff); adults who have been in contact with a case of chickenpox within the past three days; and children awaiting transplantation. The potential benefits and risks of vaccinating immunocompromised patients should be assessed on a case by case basis.

Varicella vaccination for grades 4 and 5 students: from theory to practice

BACKGROUND

In 2002-2003, as part of a pilot project, varicella vaccination was offered to susceptible students in grades 4 and 5 in schools whose health services are provided by a local community services centre in Montréal. This immunization campaign was merged with the hepatitis B immunization programme.

OBJECTIVES

To calculate the proportion of grade 4 and 5 students susceptible to varicella; to calculate the proportion of susceptible students who agree to be vaccinated; to compare the proportion of susceptibles who agree to be vaccinated when varicella vaccination is offered with the first or the second dose of hepatitis B; and to assess whether a catch-up varicella immunization programme would affect the vaccine coverage of a concurrent hepatitis B vaccination programme.

METHODS

The proportions of susceptible students and of parents of susceptibles who consented to vaccination were calculated. The proportions of parents of susceptibles who consented to vaccination were compared for both immunization strategies: varicella vaccination given with the first or second dose of hepatitis B vaccine. Logistic regression was performed to identify possible associations between consent to varicella vaccination and the various variables collected. Rates of vaccine coverage against hepatitis B after two doses were compared for the years 2000-2001 and 2002-2003.

RESULTS

Of 3,856 registered students, 3,486 (90.4%) returned consent forms. Among the 3,272 students for whom information was available, 441 (13.5%) were susceptible, including 394 (89.3%) who consented to vaccination. The rates of vaccine coverage in the schools after two doses of hepatitis B vaccine were exactly the same for the 2000-2001 and 2002-2003 school years.

CONCLUSION

Varicella vaccination of susceptible grade 4 and 5 students associated with a coincident hepatitis B vaccination campaign can be performed without negative impact on the hepatitis B vaccination programme.

Effectiveness of the Oka/GSK attenuated varicella vaccine for the prevention of chickenpox in clinical practice in Israel

BACKGROUND

The varicella Oka/Merck vaccine has been shown to be very effective in clinical practice; however, several recent studies reported reduced effectiveness. The varicella Oka/GSK vaccine (Varilrix; GlaxoSmithKline Biologicals), which has been subjected to fewer effectiveness studies, was licensed in Israel for voluntary use in 2000. This study was planned to estimate the effectiveness of the varicella Oka/GSK vaccine among children 1-5 years of age.

METHODS

Recent reports of varicella were retrieved from the Tel Aviv Health District. Two age-matched control subjects who attended the same day-care center and/or resided in the same neighborhood and had not contracted varicella in the past were recruited for each varicella case. The parents of case and control subjects were interviewed regarding the history of varicella vaccination and the severity of illness.

RESULTS

A total of 151 case subjects (mean age, 2.9 +/-1.1 years) and 298 control subjects (mean age, 3.0 +/-1.1 years) were recruited. Vaccination rates for case and control subjects were 6.6% and 38.3%, respectively (P < 0.001). Disease among vaccinated children was significantly milder, as measured by several indices, including parental perception of the illness, presence of fever, time until the lesions dried and days of day care missed. Vaccine effectiveness against varicella of any severity with these figures was 88% (95% confidence interval, 77-94%), and effectiveness against moderate/severe illness was 100%.

CONCLUSIONS

Our data demonstrate that the varicella Oka/GSK vaccine used in clinical practice is highly effective in prevention of varicella (especially moderate/severe disease) among children, including those attending day-care centers.

Associations of daycare and school entry vaccination requirements with varicella immunization rates

School and daycare entry requirements have been credited with increasing immunization rates among school-age children, but no prior study has assessed the nationwide effects of entry requirements while controlling for individual, family, and household characteristics. The 2002 National Immunization Survey (NIS) is a nationally representative annual survey that includes provider record-verified immunization dates for 20,546 children aged 19-35 months without prior history of varicella. In weighted bivariate and multivariate logistic regression models, we examined the association of state entry mandate implementation with children's up-to-date (UTD) status for varicella vaccine, adjusted for sociodemographic characteristics of children, mothers, and household income and for children's UTD status for other recommended vaccines. In this national sample representative of 5.6 million children, 83.2% (95% CI: 82.3%-84.1%) were UTD for varicella vaccine. Between 1997 and 2002 inclusive, 33 states and the District of Columbia had implemented school and/or daycare entry immunization mandates for varicella. In bivariate analyses, 84.9% (83.9%-85.9%) of children in states with varicella entry mandates were UTD, compared to 76.8% (75.3%-78.4%) of children in states without such mandates. In multivariate analyses controlling for child and family characteristics, children living in states with varicella entry mandates remained significantly more likely to be UTD for varicella than children in states without mandates. These findings indicate that immunization entry requirements are associated with higher immunization rates among preschool-age children, and suggest that the effects of entry requirements are independent of other individual and household factors associated with childhood immunization.

Recurrent papular urticaria after varicella immunization in a fifteen-month-old girl

Varicella-like rash after immunization with the live attenuated varicella vaccine is relatively common. Such vaccine-associated rashes generally consist of fewer lesions than occur in chickenpox. We describe a 15-month-old girl who experienced the onset of recurring papular urticaria after varicella immunization. The rash was varicella-like and thought by us to be caused by vaccine virus.

Vaccine effectiveness and severity of varicella among previously vaccinated children during outbreaks in day-care centers with low vaccination coverage

BACKGROUND

Varicella vaccine effectiveness (VE) during outbreaks has been reported to be 71-100% against any disease and >90% against moderate/severe disease even in day-care centers (DCCs) and schools with low vaccination rates. A recent report suggested an effectiveness rate of 44% during a DCC outbreak despite a high vaccination rate.

AIMS

To reassess vaccination coverage, VE and severity of disease among previously vaccinated children after exposure during DCC outbreaks in northern Israel, where vaccination rates are low.

METHODS

During January to June 2003, active surveillance for varicella among children in northern Israel revealed outbreaks in 8 DCCs with children 3-6 years of age. Data concerning symptoms of the disease and the age at vaccination (for previously vaccinated children) were obtained from parents and health care providers for children who contracted the disease. Analysis of VE was limited to children who were continuously enrolled in DCCs during the outbreaks.

RESULTS

The overall vaccination rate was 37%. The incidences of natural varicella and breakthrough varicella (BV) were 79 of 153 [52%; 95% confidence interval (CI) 44-60%] and 37 of 89 (41.5%; 95% CI 31-52%), respectively. VE was 20% (95% CI 0-40%) against disease of any severity and 93.4% (95% CI 75-98%) against moderate/severe disease. Ninety-four percent and 14% of children with BV and natural varicella, respectively, had mild disease (P < 0.001). The odds ratio for BV was 17 (95% CI 2.18-118) for children vaccinated >2 years before the outbreak.

CONCLUSIONS

During varicella outbreaks in DCCs with low vaccine coverage, previous vaccination provided poor protection against chickenpox, mostly among children who had been vaccinated >2 years earlier, but the disease appeared to be much milder among children with BV than among nonvaccinated children.

Evidenzbasierte Therapie von Herpes-Virus-Erkrankungen der Haut

Six questions regarding varicella-zoster virus-related skin diseases are addressed. The Cochran Library, MEDLINE, Clinical Evidence and several guideline providers were searched for evidence. The level of evidence in papers was appraised according to the Oxford Centre for Evidence-based Medicine Levels of Evidence. The current evidence for antiviral therapy of chickenpox in immunocompetent children, adults and pregnancy, recommendation of varicella vaccination, effect of time of initiation of antiviral therapy in acute zoster as well as route of treatment with regard to onset of post-zoster neuralgia are covered.

[Varicella vaccination: who should be vaccinated these days?]

In July 2004 the STIKO (German National Commission for Vaccinations) recommended routine varicella vaccination (together with the first MMR vaccination) for all healthy infants. The previous recommendations for vaccination of adolescents with no history of varicella and patient groups at risk remain valid. In persons with severely depressed cellular immunity or pregnant women vaccination with live attenuated VZV vaccines is contraindicated. Experience gained in the United States show that widespread introduction of VZV vaccination results in a decrease in both the incidence of varicella and concomitant complications including herpes zoster.

Genetic profile of an Oka varicella vaccine virus variant isolated from an infant with zoster

Varicella virus vaccine strain Oka (V-Oka) has in rare cases caused zoster in vaccinated people. Despite broad usage of V-Oka, little is known about varicella-zoster virus genomic sequence variation of strains in vaccine and isolates from patients with vaccine adverse events. Direct sequencing of 20 regions of V-Oka-GSK was compared to the sequences of the original V-Oka-Biken, GlaxoSmithKline Oka vaccine (V-Oka-GSK), and Oka-parental (P-Oka) strains. We analyzed single nucleotide polymorphisms (SNP) differentiating the Oka parental and Oka vaccine strains identified in open reading frames (ORFs) 6, 9A, 10, 21, 31, 39, 50, 51, 52, 54, 55, and 59 and eight base substitutions within ORF 62. Sixteen of these SNP impose an amino acid change in the corresponding gene product. The genotypic analysis revealed that (i) both V-Oka-GSK and V-Oka-Biken comprise mixtures of strains represented in variable proportion from lot to lot; (ii) V-Oka-GSK/zoster isolated from the zoster patient had six wild-type SNP in ORF 9A, 10, 21, 52, 55, and 62 (mutation 108838); (iii) none of the six revertant SNP would reliably discriminate Oka vaccine from the wild type; and (iv) the genomic variation found in V-Oka/zoster might be associated with changes in the biological behavior of the virus. Further studies will be needed to identify potential virulence factors in variant vaccine strains.

[Varicella vaccine]

A live virus attenuated vaccine was developed from the OKA strain (isolated from vesicles in the OKA child, 3 years of age, presenting with a benign varicella). The vaccine was completed after 11 propagation at 34 degrees C on HELF cells. The vaccine is a lyophilized preparation of a live attenuated virus, obtained by propagation of the virus in MRC-5 human diploid cell culture, titering between 1500 and 5000 cfu (colony forming unit per milliliter). This attenuated virus, contrary to the wild virus, is thermo-sensitive (39 degrees C). The rate of seroconversion after administration of one vaccine dose in healthy children, from 12 months to 12 years of age, ranges from 93% to 100% (Table 1). In controlled studies, the efficiency for the prevention of varicella in children reaches at least 85% with a 2-4 years follow-up. The prevention of severe forms is at least 95%.

Seroepidemiology of varicella-zoster virus antibodies among health-care workers and day-care-centre workers

Inclusion of live varicella vaccine in the routine occupational health vaccination schedule requires knowledge of the natural immunity to varicella zoster virus (VZV) among high-risk occupations. This study aims were to evaluate VZV antibody positivity among health-care workers (HCWs) and day-care-centre workers (DCWs) and to assess its association with potential risk factors. Three groups of workers were tested for VZV antibody positivity: hospitals and community clinic HCWs (n = 335), DCWs (n = 117) and blue-collar workers as controls (n = 121). The total VZV antibody positivity was 94.4%. There was no significant difference in VZV antibody positivity among study groups. DCWs had the lowest VZV seroprevalence (90.9%, 95% CI 85.7-96.1) and controls the highest (96.6%, 95% CI 93.2-99.9). This high VZV antibody positivity suggests that no special occupational measures are indicated in health-care or day-care occupational settings in Israel. On-going monitoring of the natural immunity to VZV is necessary to detect trends over time.

Preventing varicella-zoster disease

Varicella-zoster virus (VZV), the cause of chickenpox and shingles, is a pathogen in retreat following the introduction of mass vaccination in the United States in 1995. The live attenuated Oka vaccine, which is safe and immunogenic, gives good protection against both varicella and zoster in the short to medium term. It has undoubtedly been highly effective to date in reducing all forms of varicella, especially severe disease. However, the huge pool of latent wild-type virus in the population represents a continuing threat. Both the biology and the epidemiology of VZV disease suggest that new vaccination strategies will be required over time.

Routine vaccines across the life span, 2005

Routine vaccines include those listed on the Recommended Childhood and Adolescent Immunization Schedule and the Recommended Adult Immunization Schedule. The disease burden, rationale for vaccination, efficacy, adverse reactions, and recommendations are discussed in relation to each vaccine. Pictures of vaccine-preventable diseases are included.

Predictive value of a self-reported history of varicella infection in determining immunity in adults

The recent introduction of a vaccine for varicella has raised questions about whether, for adults, a patient's history of varicella infection is useful in determining if vaccination is necessary. We report findings on 184 family medicine patients aged 18 to 65 years who were asked if they had a history of varicella infection and were subsequently tested for varicella antibodies. A history of infection was positive for 114 (62%) of the participants and negative or uncertain for 70 (38%). All 114 subjects who reported a varicella infection history were immune. All 4 subjects who were not immune reported an uncertain or negative infection history. Except for people who are at increased risk of varicella infection or complications from infection, serologic testing may not be required for adults in the general population who have a history of varicella infection.

Efficacy of postexposure immunization with live attenuated varicella vaccine in the household setting—a pilot study

The aim of the present study was to examine the efficacy of postexposure vaccination with Varilrix in the household setting. A randomized, double-blind, placebo-controlled design was used. Twenty-two children received the varicella vaccine and 20, a placebo. The relative risk of developing varicella with a placebo compared with the vaccine was 1.1 (95% confidence interval 0.55-2.21). The risk of developing moderate to severe disease was eight times greater in the placebo group (RR=8), indicating an 80% protective effect against moderate/severe disease. The varicella vaccine Varilrix may not be effective in preventing varicella when administered after household exposure, although it is highly effective in ameliorating the disease in those who acquire it under these circumstances.

Effects of varicella vaccination on herpes zoster incidence

The effects of a general varicella vaccination programme on the incidence of herpes zoster are of major public health importance. This review focuses on two key aspects, namely the relationship between wild-type virus spread and the incidence of herpes zoster, as obtained from recent surveys, surveillance and observational studies, and the results from mathematical population models. Although knowledge is limited, close contact with varicella cases seems to have a protective effect. Thus, an increase in zoster incidence after varicella immunisation is possible, but the extent is unknown because of the influence of other factors independent of immunisation. Currently, vaccination effects estimated from mathematical modelling depend strongly on pre-specified assumptions. In order to obtain more precise predictions, the results of ongoing monitoring and clinical studies are awaited and further studies are suggested. Vaccination recommendations can be adapted at any time to take account of further findings in this area.

A review of the varicella vaccine in immunocompromised individuals

BACKGROUND

Individuals with underlying cell-mediated immunodeficiency disorders are at high risk of developing severe, life-threatening illness associated with varicella-zoster virus infection. A live-attenuated varicella vaccine is recommended for routine childhood immunisation in some countries. In healthy children, the vaccine is efficacious and safe but because immunocompromised individuals may be unable to limit replication of live-attenuated vaccine viruses, the varicella vaccine is not recommended for them and there are few exceptions.

OBJECTIVES

The purpose of this paper is to review the published studies addressing the use of the varicella vaccine in people with cell-mediated immunodeficiency disorders.

METHODS

A computerised search on the PubMed database was used to collect the relevant papers published up to March 2003.

RESULTS

The varicella vaccine has been extensively studied in susceptible children with acute lymphoblastic leukaemia in remission, but studies involving individuals with other immunodeficiency disorders are scarce. Some of the current recommendations are based on very few and small studies with short follow-up. Immunocompromised individuals should be given the varicella vaccine only with complete knowledge of their clinical and immunological conditions and after considering the risks of natural infection and vaccination.

[Reactogenicity, safety and immunogenicity of a recombinant bivaccine against smallpox and hepatitis B in limited clinical trials]

The reactogenicity of the embryonic live recombinant variola and hepatitis B bivaccine as tablets (Revax-BT) as well as its safety and immunogenicity were evaluated in clinical trials made in volunteers who had previously immunized or not with variola vaccine. A preliminary conclusion was made on a lack of side effects and drug safety in primary vaccination and been revaccination with low and high doses. Primary immunization of volunteers and as bivaccination with high doses stimulated the most pronounced immune response to the vaccine virus versus such effect observed in immunization of volunteers with low vaccine doses. Humoral immune response to HBs was observed in 75% of volunteers of both groups after as bivaccination. Such response was most pronounced in examinees immunized with low vaccine doses versus those who received high bivaccine doses. At the same time, no protective levels of humoral immunity response to HBs Ag were observed in volunteers first vaccinated.

Live viral vaccines in the control of highly infectious diseases: measles and varicella

It is possible that by the end of this decade, measles and varicella two of the most infections and previously universal diseases of children, with massive levels of morbidity and significant mortality, may become of historical interest only. To accomplish this success, it is imperative that all involved parties do what is required. The vaccine supply must be assured, parents must be appropriately educated and reinforced by the media to bring their children to be immunized, and healthcare personnel must both aggressively ascertain and administer needed immunizations.