Varivax (Merck & Co)

Varivax is a live-attenuated varicella vaccine developed and launched in the US by Merck & Co for the treatment of chickenpox [413319]. The vaccine uses the Oka strain of the varicella virus licensed from the Biken Institute at Osaka University in Japan [178223]. By June 2001, Merck was also developing the vaccine for use in adults for herpes zoster infection [413319]. The FDA required post-marketing studies as a condition for its approval of Varivax, which was granted in March 1995 [174416]. The Centers for Disease Control & Prevention Advisory Committee on Immunization Practices recommended that Varivax should be administered at the same time as the measles, mumps and rubella vaccine. Unvaccinated children between the ages of 19 months and 13 years should be vaccinated by the time they are 13 years old [180148]. Varivax, from its launch in the spring of 1995 to the end of the third quarter 1995, produced sales of US $60 million [196542]. In June 2000, a second generation of Varivax, Varivax II, was launched for vaccination against chickenpox in individuals 12 months of age and older. Varivax II prevents the transmission of chickenpox with exactly the same safety and efficacy profile as Varivax; however, the new Varivax II has the advantage of being refrigerator-stable [371871].

Current treatment practice of herpes zoster

The management of herpes zoster infection has been impacted by the development of oral and iv. antiviral therapies. There are clinical and historical features that help optimise the particular therapy course for a given patient. Additionally, there are common features of management in all patients with herpes zoster. In this review an understanding of the pathogenesis of herpes zoster is utilised as a starting point for the development of a rational approach to therapy. Clinical findings that impact decision making are emphasised and the appropriate goals for therapy are discussed.

Incidence and hospitalization rates of varicella and herpes zoster before varicella vaccine introduction: a baseline assessment of the shifting epidemiology of varicella disease

BACKGROUND

A 15-year postmarketing evaluation of the impact of varicella vaccine on the age distribution of varicella disease is being conducted at Kaiser Permanente Medical Care Program, Northern California (KPMCP). We report on a baseline assessment of the age-specific incidence and hospitalization rates of varicella and herpes zoster that was conducted before vaccine introduction.

METHODS

To assess the annual incidence of varicella, a telephone survey was conducted in a random sample of approximately 8,000 youths 5 to 19 years of age. The annual incidence of hospitalizations for varicella and herpes zoster in 1994 was assessed with the use of the computerized database at KPMCP.

RESULTS

Varicella annual incidence was 10.3% in 5- to 9-year-olds, 1.9% in 10- to 14-year-olds and 1.2% in the 15- to 19-year age groups, respectively. Hospitalization rates among the entire KPMCP membership were 2.6 and 2.1 per 100,000 person years for varicella and zoster, respectively. Varicella incidence in the 15- to 19-year age group was higher among African-Americans than among Caucasians.

CONCLUSIONS

Varicella rates were similar in the 5- to 9- and 10- to 14-year age groups to rates from other published studies conducted in 1972 to 1978, 1980 to 1988 and 1990 to 1992; however, the rate in 15- to 19-year-olds was 2 to 4 times higher than published rates in the same age category.

Zoster in patients infected with HIV: a review

Varicella-zoster virus (VZV), a member of the human herpesvirus family, causes childhood chickenpox (varicella), becomes latent in sensory ganglia, and reactivates years later in immunocompromised and elderly persons to produce shingles (herpes zoster). Early in the AIDS epidemic, zoster was noted in adults and children infected with HIV. Severe and debilitating zoster-associated dermatological, ophthalmic, and neurological complications may occur in patients infected with HIV. Antiviral therapy can modify the duration of zoster and alleviate its attendant complications. Varicella vaccine may boost the immunity and prevent virus reactivation. VZV immune globulin (VZIG) prevents or modifies clinical illness in persons who have been exposed to varicella or zoster.

Varicella-zoster infection in pediatric solid-organ transplant recipients: a hospital-based study in the prevaricella vaccine era

We reviewed 58 cases of varicella-zoster infection that occurred between 1988 and 1998 in 47 pediatric solid-organ transplant recipients. The median age of patients at the time of admission with varicella-zoster infection was 8.0 yr (range 1-17 yr). The median interval between transplantation (Tx) and varicella-zoster virus (VZV) infection was 1.6 yr (range 0.06-9.3 yr). Varicella infection occurred at a rate of one case for every seven transplant recipients. Among the 58 cases of VZV infection, 53% were varicella while 47% were herpes-zoster. Varicella infection occurred despite treatment with varicella-zoster immune globulin (VZIG) in 17 of 31 cases of varicella infection. However, the disease was generally mild with severe disease occurring in only two patients. One patient (1.7%) died as a result of bacterial sepsis. There was no significant relationship between VZV infection and specific immune suppressants. Episodes of rejection were more likely to be temporally associated with the occurence of herpes zoster than with varicella infection (p = 0.02). The data generated provide useful background information in our population in the prevaricella vaccine era.

Partial uptake of varicella vaccine and the epidemiological effect on varicella disease in 11 day-care centers in North Carolina

BACKGROUND

The increasing use of varicella vaccine in children attending day care has rapidly decreased the incidence of wild-type varicella disease. The herd immunity noted is significant and will have an effect on the epidemiology of natural varicella.

OBJECTIVE

To monitor the change in varicella incidence in day-care attendees after the licensure of varicella vaccine.

DESIGN

A prospective observational cohort study design.

SETTING

Eleven private day-care centers and preschools in North Carolina participated in the study from January 1, 1995, through December 31, 1999.

PARTICIPANTS

All children in the 11 centers were eligible for participation. Some participated more actively, supplying information on a regular basis. Others participated passively. Day-care personnel provided information about all cases of varicella.

INTERVENTIONS

None.

MAIN OUTCOME VARIABLES

The change in the incidence of varicella disease was documented as the use of varicella vaccine increased.

RESULTS

Varicella vaccine coverage increased substantially from 4.4% in 1995 to 63.1% in December 1999. The vaccination rate accelerated dramatically in 1996 and 1997, leveled off in 1998, and rose again in 1999. Cumulative varicella incidence decreased from 16.74 cases per 1000 person-months in July 1996 to 1.53 cases per 1000 person-months in December 1999 in unvaccinated children.

CONCLUSIONS

The varicella vaccination rate continued to increase slowly in the day-care population after an initial rapid uptake. The decrease in varicella disease is greater than the increase in varicella vaccination. This herd effect is welcome and even apparent in the unvaccinated children younger than 1 year.

Should health care workers in the tropics be immunized against varicella?

In tropical regions, chickenpox affects both adults and children. Therefore, healthcare workers in the tropics are vulnerable to hospital-acquired varicella infection and they may transmit infection to susceptible hospitalized individuals. Although the varicella vaccine is safe and effective, its cost is a deterrent to its use in routine immunization programmes. In order to assess whether vaccination of susceptible healthcare workers to prevent hospital-acquired transmission may be justified, we have documented the frequency of varicella among healthcare workers in our hospital. There were 96 admissions for varicella during the 1993-1997 period; staff and student nurses accounted for 76%. The peak season of admission was from February to April. The attack rate in staff and student nurses was 0.78 and 1.54 per 100 person-years, respectively. While community outbreaks of varicella occur in this region once in 4-5 years, hospital outbreaks of varicella occurred every year. This poses the risk of transmission to hospitalized patients, with serious consequences among immunocompromized individuals. Therefore, we recommend systematic selective vaccination of susceptible healthcare workers to break this cycle of annual varicella outbreaks among hospital personnel.

Pretransplant varicella vaccination is cost-effective in pediatric renal transplantation

Because of the severe complications that may result from varicella zoster virus (VZV) infection following renal transplantation (Tx), transplanted varicella-susceptible children exposed to varicella are typically given varicella zoster immunoglobulin (VZIG) as prophylaxis or are admitted and treated with parenteral acyclovir if VZIG prophylaxis fails. As both VZIG and hospitalization are costly, prevention of varicella infection by vaccination could potentially result in significant cost savings in addition to decreasing morbidity and mortality. To test this hypothesis, we developed a decision-analysis model to evaluate the cost-effectiveness of vaccinating patients with chronic renal failure (CRF) against varicella prior to renal transplant. Under baseline assumptions, vaccination for varicella pretransplant was a cost-effective strategy, with a cost of $211 per patient vaccinated compared with $1,828 per patient not vaccinated. The magnitude of cost savings from vaccination was sensitive to variations in the cost of varicella vaccine, the percentage of patients hospitalized for treatment with acyclovir, and the percentage of patients exposed to varicella infection. One- and two-way sensitivity analyses confirmed that vaccination was the dominant cost-effective strategy under all conditions examined. We conclude that vaccination for varicella pretransplant is cost-effective for patients with CRF, and that the magnitude of cost savings is sensitive to the cost of hospitalization, the percentage of patients exposed to varicella, and the cost of varicella vaccination. Pending results of ongoing studies of the safety and efficacy of VZV vaccine in children with CRF, we recommend that VZV vaccine be given to all children with CRF.

Safety and immunogenicity of live attenuated varicella vaccine in 9-month-old children

BACKGROUND

The present study was conducted to evaluate the safety and immunogenicity of live attenuated varicella vaccine (Oka-strain) in 9-month-old infants.

METHODS

One hundred and fourteen infants were vaccinated once with live attenuated varicella vaccine (Valrix; SmithKline Beecham Biologicals, Rixensart, Belgium) containing a mean virus titer of 10(4.0) plaque-forming units (p.f.u.) per dose. Signs and/or symptoms after vaccination were followed for 42 days. Home visits were made to detect solicited local reactions (0-3 days) and solicited general reactions (0-21 days), as well as unsolicited reactions. Specific varicella antibodies were determined by an indirect immunofluorescence method. The geometric mean titer and seroconversion rate were calculated.

RESULTS

Signs and/or symptoms were reported in 47.4% (54/114) of cases following vaccination. The only local symptom reported was pain on digital pressure at the injection site and this was reported in 28.1% (32/114) of infants. General symptoms were reported in 38.6% (44/114) of cases. The most frequently reported findings were fever (27.2%), which was mostly mild, restlessness (20.2%) and cough (11.4%). Only four unsolicited symptoms were reported and they were all unrelated to vaccination. No serious adverse event was reported. Of the 109 infants included in the immunogenicity analysis, 105 were seronegative and four were seropositive for antibodies against varicella before vaccination. The vaccine elicited seroconversion in 97.1% of initially seronegative cases. The post-vaccination geometric mean titer for these infants was 30.9 geometric mean titer (GMT).

CONCLUSIONS

The vaccine was found to be safe and immunogenic when given to infants as young as 9 months of age. This may be of clinical significance during outbreaks of varicella and especially for developing countries.

Varicella virus vaccine before pregnancy. Important breakthrough in protecting fetuses

QUESTION

Now that the new varicella virus vaccine is available, should I vaccinate all my female patients of reproductive age who do not remember having had chickenpox in childhood?

ANSWER

In North America, seven out of 10 women who do not remember having chickenpox in childhood actually had it and are immune. You should test their immunity and, if they are susceptible, vaccinate them. Ensure they are not pregnant at the time of vaccination because the vaccine's safety has not been proven.

Varicella mortality: trends before vaccine licensure in the United States, 1970-1994

We examined varicella deaths in the United States during the 25 years before vaccine licensure and identified 2262 people who died with varicella as the underlying cause of death. From 1970 to 1994, varicella mortality declined, followed by an increase. Mortality rates were highest among children; however, adult varicella deaths more than doubled in number, proportion, and rate per million population. Despite declining fatality rates, in 1990-1994, adults had a risk 25 times greater and infants had a risk 4 times greater of dying from varicella than did children 1-4 years old, and most people who died of varicella were previously healthy. Varicella deaths are now preventable by vaccine. Investigation and reporting of all varicella deaths in the United States is needed to accurately document deaths due to varicella, to improve prevention efforts, and to evaluate the vaccine's impact on mortality.

Facts and fallacies about varicella and the varicella vaccine

Varicella is a nearly ubiquitous infection that results in significant morbidity and occasional mortality. The varicella vaccine has been licensed in the United States for the past five years. While varicella vaccination rates are slowly growing nationally, the immunization rate for South Dakota remains abysmally low. The legislature has recently mandated this vaccine for school entry in South Dakota, to promote its increased use. There are many fallacies about varicella and the varicella vaccine and questions about how new requirements of varicella vaccination before school entry will be met. This article identifies these common misconceptions and can serve as a resource for answers to questions commonly asked of vaccine providers.

Incidence, risk factors and outcome of varicella-zoster virus infection in children after haematopoietic stem cell transplantation

We report a retrospective analysis of VZV infection after haematopoietic stem cell transplantation (HSCT) in children. Thirty-three (30%) of the total 109 children who were transplanted during a 7 year period developed post-transplant VZV infection. Twenty-four of these 33 (73%) children had VZV infection within 1 year following HSCT. The cumulative incidences of post-transplant VZV infection at 1 and 5 years were 26% and 45%, respectively. The positive and negative predictive values of pretransplant VZV serology in recipients on the development of HZ following HSCT were 39% and 88%, respectively. Pretransplant VZV seropositivity in recipients was the only risk factor for post-transplant herpes zoster (HZ) infection on multivariate analysis. All patients responded to acyclovir. The median duration of VZV infection was 5 days. Three (11%) and one (3%) children with HZ developed visceral dissemination and post-herpetic neuralgia, respectively. No mortality was directly attributed to VZV infection. VZV infection remains a major cause of morbidity in children after HSCT. Further studies are warranted to evaluate the potential use of VZV vaccine in these children. Bone Marrow Transplantation (2000) 25, 167-172.

Varicella outbreaks after vaccine licensure: should they make you chicken?

In 1998, 3 years after vaccine licensure, child care centers (CCC) in Los Angeles County continued to report varicella outbreaks. We investigated outbreaks at 2 CCCs to determine the cause for them, such as low vaccination coverage levels or unexpected low vaccine effectiveness. We collected information on past history of varicella, illness during the outbreak, and prior varicella vaccination among CCC attendees. We found that CCC "H" had a vaccination coverage of 87% (34/39) compared with 30% (6/20) in CCC "L." The overall attack rate was lower in CCC "H" (31%) than in "L" (61%; P value =.03). Vaccine effectiveness for any varicella was 71% in "H" and 100% in "L." Vaccinated children with varicella had milder disease than unvaccinated. In conclusion, we found varicella outbreaks in CCCs with both high and low vaccination coverage. Vaccine effectiveness was within the range predicted by the literature. Vaccination led to a lower attack rate in the highly vaccinated CCC and appeared to protect from severe disease.

Varicella vaccine in non-immune household contacts of children with cancer or leukaemia

OBJECTIVE

To assess the immunogenicity and reactogenicity of a new formulation of live attenuated varicella vaccine (Oka strain) in non-immune household contacts of children with cancer or leukaemia.

METHODOLOGY

This was an open study with one group. Healthy varicella-susceptible adults and children living in the same household as children with cancer or leukaemia were vaccinated with a new live attenuated varicella vaccine (Oka strain) which is stable when stored at 2-8 degrees C (refrigerator temperature) for at least 24 months (Varilrix). Children less than 13 years of age received one dose (0.5 mL containing at least 103.3 plaque forming units) by subcutaneous injection and those aged over 13 years received two doses 8 weeks apart. Adverse reactions following vaccination were recorded daily by the vaccinees. Post-vaccination antibody estimation was determined using indirect immunofluorescence 6 weeks after vaccination.

RESULTS

Thirty-five seronegative subjects (28 children and 7 adults and adolescents) were vaccinated. All subjects tested (34) had seroconverted after vaccination. Local injection site reactions were experienced by 15/35. Other adverse reactions were uncommon (rash 2/35, fever (>/= 37.5 degrees C) 3/35). No cases of clinical varicella occurred amongst the high-risk household contacts of the vaccine.

CONCLUSION

This is the first study of this formulation of varicella vaccine in household contacts of children with cancer or leukaemia. The vaccine was found to be safe and immunogenic, but further follow-up is needed to document duration of immunity.

Cellular immune response of a varicella vaccine following simultaneous DTaP and VZV vaccination

BACKGROUND

Chickenpox and zoster are an important cause of morbidity among children and adults. The ability of a new, thermostable vaccine to induce varicella-zoster-virus (VZV)-specific humoral and cell mediated immunity when given simultaneously with diphtheria-tetanus-acellular pertussis vaccine (DTaP) as a booster dose in the second year of life was investigated.

METHODS

A new, temperature stable varicella vaccine (OKA-strain, SB-Biologicals, Rixensart, Belgium) was given simultaneously with a booster dose of DTaP vaccine. VZV-specific humoral and cell-mediated immunity was studied in the first 27 out of 232 vaccinated children at 16-28 months of age, from blood samples drawn just before and six weeks after vaccination. VZV-specific antibody response, T-cell proliferation, cytokine production and expression of activation markers (CD25, HLADR) on T-cells were analyzed.

RESULTS

Vaccination resulted in a significant rise of VZV-specific serum IgG titers and in a strong VZV-specific T-cell response in all vaccinated infants. Analysis of the expression of activation marker revealed activation of both CD4+-T-helper- and CD8+-T-cells.

CONCLUSIONS

The varicella vaccine given simultaneously with DTaP produced strong B- and T-cell responses alike. This is the first report to show that CMI to VZV is conferred to young children by vaccination with a temperature stable VZV vaccine.

Varicella vaccination of health-care workers

The objective of this open study was to evaluate the response of non-immune health-care workers to two doses of live attenuated varicella vaccine given two months apart. One hundred subjects (58 females; aged 17-49 yr, mean 22.8 yr) received two doses of varicella vaccine. Blood samples for antibody estimation were taken before vaccination, 2 months after the first dose and 6 weeks after the second dose. Reactions were recorded daily in diaries by the vaccinees and controlled by telephone contacts by the investigators. Ninety-four of 99 vaccinees (94.9%, 95% CL 88.6, 98.3) had detectable antibodies after the first dose [titers 4-1024, geometric mean titer (GMT): 53.2 (95% CL 42.4, 66.8)]. After the second dose, all vaccinees had antibodies (100%, 95% CL 96.6, 100.0) [titers 32-2048, GMT: 235.6 (95% CL 199.0, 278.8)]. Mild reactions limited to the injection site occurred in 1 in 4 subjects after each dose. Vesicular rashes occurred in one subject after the 1st dose and in 3 subjects after the 2nd dose, 1 subject was febrile (38.2 degrees C) after the 1st dose. Eighty-one subjects were retested 12 months after the second vaccination. Three had become seronegative (one developed mild varicella 2 months later). Two had boosted their titers (one after mild clinical varicella 1 month earlier, the other after close contact with clinical cases). The GMT of the group had fallen to 83.6 (95% CL 65.4, 106.8). The identification and vaccination of seronegative health-care workers is safe and efficient, and will benefit the workers themselves and the communities in which they work.