Prevention and treatment of VZV infections in patients with HIV

Varicella zoster virus (VZV) infections in human immunodeficiency virus (HIV)-infected patients are known to have a different disease spectrum from that seen in other types of patients. Varicella in children with HIV infection is likely to be more serious than in otherwise healthy children and routine antiviral therapy is recommended. There is evidence that the development of varicella in HIV-infected children is not associated with progression to AIDS, suggesting that it may be safe to immunize HIV-infected children with live attenuated varicella vaccine. There are no published data on varicella in HIV-infected adults, however, probably because most adults have already experienced varicella prior to HIV infection. Zoster in HIV-infected children differs somewhat from that in HIV-infected adults. In particular, HIV-infected children who develop varicella in the setting of severe immunodeficiency are at an especially high risk to develop zoster. Given the low rate of toxicity of aciclovir as well as its ease of administration and its efficacy in hastening the healing of VZV infections, prompt treatment with this antiviral agent is recommended for both HIV-infected children and adults. Foscarnet should be used for zoster that is strongly suspected or proven to be caused by aciclovir-resistant VZV. Patients with HIV for whom there is no evidence of significant immunosuppression and who have not had varicella should be immunized with live attenuated varicella vaccine as a preventative measure for both varicella and zoster. It is hoped that immunization of VZV seropositive HIV-infected patients will decrease the incidence of zoster. Studies to determine this are under way.

Persistence of immunity to varicella-zoster virus after vaccination of healthcare workers

OBJECTIVE

Varicella-zoster virus (VZV) vaccine is recommended to protect susceptible healthcare workers (HCWs) from serious disease and to prevent nosocomial spread of VZV. We evaluated clinical outcomes and serological responses in HCWs after immunization with live attenuated VZV vaccine.

DESIGN

Vaccinees were immunized from 1979 to 1998 during VZV vaccine trials, as well as after licensure, and followed prospectively for 1 month to 20.6 (mean 4.6) years after vaccination. Sera were tested by fluorescent antibody to membrane antigen (FAMA), latex agglutination (LA), and enzyme-linked immunoassay (EIA) to detect VZV-specific antibodies.

STUDY PARTICIPANTS

The median age of the 120 HCWs was 26 years; 51 (42%) were males.

INTERVENTIONS

Ninety eight (82%) of these study subjects received vaccine prepared by Merck and 22 (18%) by SmithKline Beecham; 25, 81, and 14 vaccinees received one dose, two doses, and three doses, respectively.

RESULTS

The crude attack rate was 10%; 12 of 120 HCWs developed chickenpox 6 months to 8.4 years after vaccination. The attack rates following household and hospital exposures were 18% (4/22) and 8% (6/72), respectively. All resulting illness was mild to moderate (mean 40 vesicles). Seroconversion after vaccination was documented by FAMA in 96% of HCWs, although 31% lost detectable antibodies. Compared with FAMA, LA and EIA were 82% and 74% sensitive and 94% and 89% specific, respectively.

CONCLUSIONS

The VZV vaccine effectively protected HCWs from varicella, particularly from serious disease. Currently available serological tests are not optimal, and improved assays are needed.

Long-term persistence of cellular immunity to Oka vaccine virus induced by pernasal co-administration with Escherichia coli enterotoxin in mice

A mutant of Escherichia coli enterotoxin induced cellular immunity to a live varicella vaccine (the Oka strain) as a mucosal adjuvant in mice. The persistence of this cellular immunity was investigated. A commercially available live Oka vaccine virus and toxin were administered once simultaneously via the nasal route, in mice. Ten or 12 months later, a delayed-type hypersensitivity to the vaccine virus was detected by footpad test, but an antibody neutralizing the varicella-zoster virus was not. When spleen cells from mice immunized with the vaccine and toxin were re-stimulated by live vaccine in vitro, their thymidine uptake and IL-2 production were higher than those from mice immunized with the vaccine alone, but lower than those of spleen cells prepared from mice 2 months after nasal administration. Production of IL-4 in these cells, however, was not induced by re-stimulation in vitro. These results suggest that although humoral immunity for Oka vaccine virus is only weakly induced by one co-administration of the vaccine and toxin, cellular immunity is induced and maintained over 1 year, though it declines with age. The nasal administration of the vaccine and toxin might be effective for maintaining cellular immunity to the varicella-zoster virus long term.

Vaccines for transplant recipients

Immune dysregulation and immunosuppression regimens impact on the ability of transplant recipients to respond to immunizations. The distinct challenges of immunizations to benefit stem cell transplant recipients and solid organ transplant recipients are discussed separately. Recommended vaccines for stem cell transplant recipients and solid organ transplant candidates are suggested. New approaches to consider to enhance immune responses of transplant recipients are discussed.

Live-attenuated varicella vaccine

This article reviews the history and development of live attenuated varicella vaccine from its early days in Japan to its widespread use throughout the world. The vaccine has proven extremely safe after immunization of as many as 10 million healthy children and adults in the United States alone. The vaccine is also highly immunogenic and offers close to 100% protection from severe chickenpox and 90% protection from illness. It is expected to have a major impact on the epidemiology of varicella and zoster in countries with high vaccine uptake.

Varicella vaccine in post-exposure prophylaxis

Evidence concerning the effectiveness of Oka-based varicella vaccines when administered following exposure to varicella zoster virus in domestic and hospital settings is reviewed. The evidence appears to support post-exposure use of Oka-derived varicella vaccines in children within 3 days of rash onset in the index case. Despite vaccination, a small proportion will develop mild, but infectious, chickenpox, especially if they have been exposed in the household setting. Controlled studies of post-exposure prophylaxis in adults using both Varilrix and Varivax II are still needed. The applicability of this approach to disease control in health care facilities and in community settings warrants wider discussion.

Adjuvant action of Escherichia coli enterotoxin for delayed-type hypersensitivity to Oka vaccine virus on pernasal co-administration in mice

The usefulness of a mutant of Escherichia coli enterotoxin for the induction of cellular immunity to varicella-zoster virus as a mucosal adjuvant is assessed in mice. When a commercially available live varicella vaccine (the Oka strain) and toxin were once administered simultaneously via the nasal route, delayed-type hypersensitivity to Oka vaccine virus was significantly induced and detected by footpad test in mice. Moreover, when spleen cells from mice immunized with the vaccine and toxin were re-stimulated with live vaccine in vitro, they showed more thymidine uptake and produced more IL-2 than those from mice immunized with the vaccine alone. These results suggest that mutant enterotoxin has adjuvant action to induce a specific delayed-type hypersensitivity to Oka vaccine virus on nasal co-administration with live vaccine virus.

Minimum estimated incidence in Japan of anaphylaxis to live virus vaccines including gelatin

We have previously found that most occurrences of anaphylaxis to live virus vaccines are caused by gelatin present in the vaccines as a stabilizer. After we published the evidence for the role of gelatin in anaphylaxis, vaccine manufacturers in Japan began to eliminate gelatin from live virus vaccines. In the present study, we tried to estimate its incidence before the gelatin elimination was started. Physicians and vaccine manufacturers submitted serum samples from children with anaphylaxis to measles, mumps, rubella or varicella vaccine to National Institute of Infectious Diseases (NIID) for 3 years from April 1994 to March 1997. Specific IgE to gelatin was assayed at NIID or two manufacturers by the CAP and ELISA methods. There were 44 children with life-threatening severe anaphylaxis (airway obstruction or anaphylactic shock) during the 3-year period, 41 of whom had anti-gelatin IgE. There were 64 children with mild anaphylaxis (without airway obstruction); 62 had anti-gelatin IgE. There were 100 children with only systemic cutaneous signs; 81 had anti-gelatin IgE. The estimates for the incidence of the severe anaphylaxis in 1994-1996 are: 6.84, 7.31, 4. 36, and 10.3 cases per million doses of gelatin-containing measles, rubella, mumps, and varicella vaccines, respectively.

Endocarditis attributable to group A beta-hemolytic streptococcus after uncomplicated varicella in a vaccinated child

Varicella is generally a benign, self-limited childhood illness; however, severe, life-threatening complications do occur. A live, attenuated vaccine exists to prevent this illness, but controversy remains concerning the need to vaccinate children for what is generally a benign, self-limited disease, although more states are currently recommending this vaccine. We report a previously healthy 3-year-old who developed varicella 6 months after vaccination with no apparent skin superinfections, who subsequently developed group A beta-hemolytic streptococcus (GABHS) bacteremia resulting in endocarditis of a normal heart valve. We are unaware of previous reports of endocarditis related to GABHS after varicella. After developing a harsh, diastolic murmur that led to an echocardiogram, aortic valve endocarditis was diagnosed. A 6-week course of intravenous penicillin G was administered. Two weeks after the initiation of therapy, the diastolic murmur was harsher, and echocardiography revealed a large vegetation on the posterior leaflet of the aortic valve, with severe aortic insufficiency and a dilated left ventricle. The patient subsequently developed congestive heart failure requiring readmission and aggressive management. One month after the initial echocardiogram, a repeat examination revealed worsening aortic regurgitation and mitral regurgitation. The patient received an additional 4 weeks of intravenous penicillin and gentamicin followed by aortic valve replacement using the Ross procedure. Our patient, the first reported case of bacteremia and endocarditis from GABHS after varicella, illustrates the need for the health care practitioner to consider both common and life-threatening complications in patients with varicella. While cellulitis, encephalitis, and septic arthritis may be readily apparent on physical examination and commonly recognized complications of varicella, the possibility of bacteremia without an obvious skin superinfection should also be entertained. The case we report is unique in that the patient had normal immune function, had been previously vaccinated, and developed a rare complication of varicella-endocarditis-in a structurally normal heart with a previously unreported pathogen. Although a child may have been vaccinated against varicella, the chance of contracting the virus still exists and parents should be informed of this risk. group A beta-hemolytic streptococcus, endocarditis, varicella, Varivax, complications of varicella.

Comparison of a live attenuated and an inactivated varicella vaccine to boost the varicella-specific immune response in seropositive people 55 years of age and older

Healthy, varicella-zoster virus (VZV)-seropositive subjects, aged 55-89 years (mean age 66 years), received either 4000 PFU of live, attenuated VZV vaccine (n=85) or an equal volume of this vaccine that was heat-inactivated (n=82). Both vaccines significantly boosted VZV antibody (enzyme immunoassay) and gamma-interferon production by peripheral blood mononuclear cells stimulated by VZV antigen. These responses returned to baseline by 12 months. Circulating mononuclear cells that proliferated in response to VZV antigen were significantly more numerous (responder cell frequency assay) after either vaccine, and persisted with a half-life of 17. 5-21.3 months. There were no differences in immune response to either vaccine in this older age cohort.

Cost effectiveness of vaccination strategies in adults without a history of chickenpox

PURPOSE

Some authorities recommend varicella antibody testing or vaccination for adults without a history of chickenpox, but the cost effectiveness of these interventions is uncertain.

SUBJECTS AND METHODS

Using a Markov decision model, we estimated the cost effectiveness of three strategies for adults with no history of chickenpox: no vaccination, varicella antibody testing followed by vaccination for those without antibody, and vaccinating all. Societal and third-party payer perspectives were taken, with costs and benefits discounted at 3% per year. Assumptions for the baseline analysis were chosen to bias against no vaccination.

RESULTS

In the baseline analysis for 20- to 29-year-old patients, testing followed by vaccination compared with no vaccination is cost saving from a societal perspective and costs $6,670 per quality-adjusted life-year (QALY) gained from a third-party payer perspective. When less favorable assumptions are used, results are sensitive to the rates of compliance with vaccination follow-up; testing followed by vaccination costs more than $50,000 per QALY if <75% comply. For patients 30 years of age and older, the incremental cost of testing followed by vaccination is at least $97,100 per QALY compared with no vaccination, with costs greater than $50,000 per QALY unless testing costs less than $7.73, the chickenpox case-fatality rate is >0.067% (baseline 0.025%), or immunity with no chickenpox history is <25% (baseline 71%). In either age group, vaccinating all has an incremental cost of $2 to $16 million per QALY gained compared with testing followed by vaccination.

CONCLUSION

Testing followed by vaccination for varicella in US adults aged 20 to 29 years may be cost effective by conventional criteria but is sensitive to rates of compliance with vaccination protocols. Testing or vaccination of older adults is expensive but may be cost effective in patients with lower probabilities of immunity or in those who have a greater risk of complications from chickenpox.

Varicella vaccination: evidence for frequent reactivation of the vaccine strain in healthy children

Wild-type varicella zoster virus (VZV) causes chickenpox, a common childhood illness characterized by fever and a vesicular rash and rare serious complications. Wild-type VZV persists in a latent form in the sensory ganglia, and can re-activate to cause herpes zoster. More than 10 million American children have received the live attenuated Oka strain VZV vaccine (OkaVZV) since its licensure in 1995. Pre-licensure clinical studies showed that mean serum anti-VZV levels among vaccinees continued to increase with time after vaccination. This was attributed to immunologic boosting caused by exposure to wild-type VZV in the community. Here, we examine the alternative, that large-scale asymptomatic reactivation of OkaVZV might occur in vaccinees. We analyzed serum antibody levels and infection rates for 4 years of follow-up in 4,631 children immunized with OkaVZV. Anti-VZV titers decreased over time in high-responder subjects, but rose in vaccinees with low titers. Among subjects with low anti-VZV titers, the frequency of clinical infection and immunological boosting substantially exceeded the 13%-per-year rate of exposure to wild-type varicella. These findings indicate that OkaVZV persisted in vivo and reactivated as serum antibody titers decreased after vaccination. This has salient consequences for individuals immunized with OkaVZV.

Parental attitudes toward varicella vaccination. The Puget Sound Pediatric Research Network

OBJECTIVES

To evaluate parental health beliefs regarding the varicella vaccine and to identify potential areas for interventions designed to increase immunization against varicella.

SETTING

Data were collected in the offices of pediatricians who are members of the Puget Sound Pediatric Research Network, a regional practice-based research group in the Seattle, Wash, area.

METHODS

At the time of an office visit, parents were asked to complete a survey on the varicella vaccine. Respondents indicated level of agreement with 10 health belief statements regarding the immunization using a 6-point Likert scale from "completely agree" to "completely disagree"; responses were subsequently transformed to an ordinal scale from 1 to 6, with 6 corresponding to highly positive beliefs. A composite health belief score for each respondent was computed by averaging responses to all statements. Parents also were asked to indicate the level of influence of their child's pediatrician on their decision to use the varicella vaccine.

RESULTS

A total of 598 surveys were completed. Generally, parents agreed that the vaccine was worthwhile even if the only benefit was preventing a rare complication. Conversely, the majority of parents disagreed that varicella vaccine was worthwhile if the only benefit was preventing lost time from work, and that the immunization was worthwhile even if immunity was not lifelong. Parents who indicated that their child's pediatrician's opinion significantly influenced their decision to use the vaccine had higher composite health belief scores than those who indicated less influence (median scores, 4.3 and 4.0, respectively; P<.001).

CONCLUSIONS

In this sample, parents had more positive health beliefs about the ability of varicella vaccine to prevent rare complications than to save time lost from work. These data also suggest that pediatricians can have an important role in increasing positive health beliefs about the vaccine. These findings may help future interventions to increase the immunization rate against varicella.

Centers for Disease Control and Prevention (CDC). Vaccination coverage among adolescents 1 year before the institution of a seventh grade school entry vaccination requirement--San Diego, California, 1998

In 1996, the Advisory Committee on Immunization Practices, the American Academy of Pediatrics, the American Association of Family Physicians, and the American Medical Association recommended routine health-care visits for children aged 11-12 years, emphasizing vaccination with hepatitis B vaccine; measles, mumps, and rubella vaccine (MMR); tetanus and diphtheria toxoids (Td); and varicella vaccine. Because no national data exist regarding vaccination coverage among adolescents, the impact of these recommendations is unknown. In October 1997, California enacted Assembly Bill 381 (AB381) that requires students entering the seventh grade on or after July 1, 1999, to have received three doses of hepatitis B vaccine and two doses of MMR. To assist in planning and implementing AB381, the San Diego County Health Department expanded its 1998 infant and adult vaccination survey to include fifth and sixth graders. This report summarizes the findings from that survey, which indicate that most fifth and sixth graders lacked required and recommended vaccinations.

Postexposure effectiveness of varicella vaccine

OBJECTIVE

1) To describe the postexposure effectiveness of varicella vaccine in a homeless shelter; and 2) to demonstrate an effective public health intervention and its implications.

DESIGN

A prospective observational study.

SETTING

A women and children's shelter in Philadelphia with 2 cases of varicella before intervention.

OUTCOME MEASURES

Varicella in vaccinated and unvaccinated shelter residents; vaccine effectiveness for prevention of varicella when administered after exposure among children <13 years of age.

RESULTS

Sixty-seven shelter residents received varicella vaccine after exposure, including 42 children <13 years of age. One child who was unvaccinated developed varicella, but no vaccinated child developed typical disease. Vaccine effectiveness was 95.2% (95% CI, 81.6%-98.8%) for prevention of any disease and 100% for prevention of moderate or severe disease among the children <13 years of age.

CONCLUSION

When used within 36 hours after exposure to varicella in a setting where close contact occurred, varicella vaccine was highly effective in preventing further disease. This study provides support for the recent recommendation by the Advisory Committee on Immunization Practices to administer varicella vaccine after exposure: this practice should minimize the number of moderate or severe cases of disease and prevent prolonged outbreaks.

Live varicella vaccine in both immunocompromised and healthy children

BACKGROUND

There is no information on the use of live varicella vaccine in Mexican children. Our objective was to evaluate antibody response and safety of the live varicella vaccine in both healthy and immunocompromised Mexican children.

METHODS

One hundred children with no history of varicella/zoster were vaccinated with a live attenuated varicella vaccine. According to their immune status, patients were divided into either a compromised (leukemia, solid tumors, chronic renal failure, and cirrhosis) or a healthy children group. Serum IgG antibodies against VZV were measured by ELISA at baseline and at 3 and 6 months after vaccination.

RESULTS

A positive VZV-ELISA at baseline was detected in 36 of 67 (53.7%) immunocompromised children and in 22 of 33 (66%) healthy children. Among VZV-seronegative children, seroconversion at 6 months post-vaccination was observed in 90.3% of compromised children and in 100% of healthy children. Increases in serum antibody levels at 3 and 6 months post-vaccination was similar in both groups. VZV vaccine-related adverse reactions, mostly mild and local, were detected in 29% of the children. Three compromised children had a mild rash symptomatic of varicella after vaccination.

CONCLUSIONS

About 50% of immunosuppressed children (mean age 8.8 +/- 3.6 years) with no varicella history were VZV-seronegative. Almost all of these compromised VZV-seronegative patients seroconverted 6 months after vaccine. In addition, antibody titers were similar in both compromised and healthy children.

American Academy of Pediatrics. Committee on Infectious Diseases. Varicella vaccine update

Recommendations for routine varicella vaccination were published by the American Academy of Pediatrics in May 1995, but many eligible children remain unimmunized. This update provides additional information on the varicella disease burden before the availability of varicella vaccine, potential barriers to immunization, efforts to increase the level of coverage, new safety data, and new recommendations for use of the varicella vaccine after exposure and in children with human immunodeficiency virus infections. Pediatricians are strongly encouraged to support public health officials in the development and implementation of varicella immunization requirements for child care and school entry.

[Varicella vaccine]

Varicella vaccine has been extensively studied in Japan, the United States and Canada since 1974. Its efficacy in healthy children is good, on the order of 94%. It also has a good efficacy in immunocompromised children, such as children treated for acute leukemia or malignant tumors. However, the vaccine has to be administrated during a 2-3 week transient suppression of chemotherapy. In the USA, varicella vaccination is recommended for receptive adults who are particularly exposed to varicella, such as health professionals working with immunocompromised patients. Benefits and cost analysis of a generalized varicella vaccination in children has shown that it would be beneficial due to the cost of parents' work leave during the children's illness.

Parental knowledge, attitudes, and demand regarding a vaccine to prevent varicella

BACKGROUND

Maintenance of high immunization rates is challenged by frequent changes to the recommended immunization schedule. This study assessed parent-reported knowledge of, attitudes about, and demand for a new vaccine against varicella.

METHODS

Six months following licensure of the varicella vaccine, a cross-sectional study was conducted by mailed survey among a sample of parents of 23- to 35-month-old children. Effective response rate was 65%.

RESULTS

Three quarters of parents had heard about the vaccine to prevent varicella. The lay media was the most frequently mentioned source of information. Thirteen percent of parents had already obtained the vaccine for their child, another quarter planned to get it, and one half were undecided. The most frequently cited factor influencing parents who had obtained or intended to obtain the vaccine was their doctor's recommendation. For those undecided or not inclined to get the vaccine, insufficient information about the vaccine was the most frequently listed factor.

CONCLUSION

Publicizing a new vaccine through the media may be effective in raising public awareness, but detailed information about the vaccine and the recommendation of providers is still important in a parent's decision about the vaccine for their child.

Seroconversion rates in healthcare workers using a latex agglutination assay after varicella virus vaccination

OBJECTIVES

To determine the seroconversion rate after varicella immunization of healthcare workers (HCWs) and the effect of seroconversion rate on current cost-based recommendations for universal vaccination.

METHODS

A voluntary vaccination program for HCWs was performed at a tertiary-care cancer center in New York City. A commercial latex agglutination assay was used to test postvaccination antibody response. Costs for vaccination and postvaccination serological testing were compared to potential costs of postexposure employee furloughs.

RESULTS

Of 263 seronegative HCWs, 96 (36.5%) began the vaccine program. Thirty-nine HCWs received only one dose of vaccine. Seven returned for follow-up antibody testing, of whom 4 were seropositive. Of the 57 HCWs who received two doses, 38 returned for follow-up serology. Thirty-one (81.6%) HCWs were seropositive for varicella-zoster virus antibodies, and seven HCWs (18.4%) remained seronegative. Total cost of vaccination for all 263 seronegative HCWs was estimated and compared to the cost of varicella-related furloughs at our institution.

CONCLUSIONS

We found a considerably lower rate of vaccine-induced seroconversion at our hospital compared to that of the published literature. Despite this finding, universal varicella vaccination remained an extremely cost-effective alternative to the furloughing of exposed, seronegative HCWs. Projected hospital savings exceeded $53,000 in the first year after vaccination alone.

Prevention of varicella. Update recommendations of the Advisory Committee on Immunization Practices (ACIP)

In February 1999, the Advisory Committee on Immunization Practices (ACIP) expanded recommendations for varicella (chickenpox) vaccine to promote wider use of the vaccine for susceptible children and adults. The updated recommendations include establishing child care and school entry requirements, use of the vaccine following exposure and for outbreak control, use of the vaccine for some children infected with the human immunodeficiency virus (HIV), and vaccination of adults and adolescents at high risk for exposure. These recommendations also provide new information on varicella vaccine postlicensure safety data.

Varicella immunity: persistent serologic non-response to immunization

OBJECTIVE

Varicella-zoster (VZV) infection is an occupational hazard for health care workers. The "gold standard" for assessing protection is a positive antibody titer. We present a case of persistent serologic non-responsiveness following VZV immunization and discuss a management strategy.

METHODS

A 29-year-old woman, immunocompetent pediatric resident was repeatedly removed from her clinical duties because of a negative history of chicken pox and the absence of a VZV antibody titer. She received a total of three doses of the VZV vaccine and continued to have a negative antibody titer as measured by a commercial ELISA assay (Wampole). Subsequently, she had three direct contacts with infectious children and did not develop clinical chicken pox.

RESULTS

A lymphocyte proliferation assay was performed using inactivated varicella vaccine and tetanus antigens. The patient's varicella and tetanus stimulation index (SI) were 46.5 and 42, respectively. The SI for the positive control (a patient recently recovered from a wild type infection) were 144 (varicella specific), and 114 (tetanus). The SI secondary to VZV antigens reported in the literature is 30.5 +/- 9.1. We reassessed the varicella antibody titer using more sensitive assays: fluorescent antibody to membrane antigen and latex agglutination. Both tests verified the presence of VZV specific IgG at a titer of 1:8 in our patient.

CONCLUSION

This case illustrates that in a subgroup of individuals the antibody response to VZV vaccine may be low despite an adequate cell-mediated response. Commercial VZV ELISA assays were designed to measure higher titers associated with natural infection rather than the lower titer induced by the vaccine. Repeated immunizations plus more sensitive measures of VZV-specific IgG should be used to validate protection rather than the current commonly utilized ELISA screening. Clinicians should be aware of the variability in VZV-specific antibody assays when assessing post VZV vaccine titers prior to determining protection in health care workers.

Varicella immunization practices and the factors that influence them

OBJECTIVES

To evaluate the varicella immunization practices of physicians in Rochester, NY, and to identify factors that predict whether physicians administer varicella vaccine to children.

DESIGN

Evaluation of a 40-item survey addressing varicella immunization practices and opinions about varicella immunization that was sent to 241 pediatricians and family physicians.

RESULTS

A total of 172 physicians (71.4%) completed the survey. Sixty-three percent administer the vaccine to some or all varicella-susceptible children aged 1 through 5 years, while 57% administer it to children aged 6 through 11 years, and 74% administer it to adolescents 12 years and older. Physicians who did not offer the immunization were more likely to believe that (1) the vaccine should not be given to preadolescent children because "varicella is a normal part of childhood"; (2) by giving the vaccine, varicella may shift from being primarily a childhood illness to being primarily an adult illness; (3) children get enough immunizations already and should not be given additional immunizations to prevent varicella; (4) it may be preferable to only immunize immunocompromised individuals and their close contacts; and (5) it would cost too much to immunize all American children who have not had varicella. Physicians most likely to offer the vaccine were pediatricians and those whose patients were covered primarily by private insurance plans. After becoming aware of morbidity and mortality rates for varicella-related complications, many physicians who did not administer the vaccine, or administered it only at the request of a parent, indicated that they would be more likely to offer it.

CONCLUSIONS

Most physicians in the Rochester area administer varicella vaccine, especially to adolescents 12 years and older. Specialty, predominant insurance type billed, and various opinions characterized those who did not offer the immunization. Providing these physicians with information about varicella-related complications may make them more likely to immunize.

[Vaccination of chickenpox in children with acute lymphoblastic leukaemia]

Varicella vaccine has shown its efficacy to prevent the disease and complications in healthy and immunodeficient children. In this article the authors evaluate the immunologic status of acute lymphoblastic leukaemia at diagnosis and at follow up and the development of chickenpox and/or herpes zoster. Children with negative serology and continuous complete remission of acute lymphoblastic leukaemia for one year were vaccinated. Of 71 children diagnosed of acute lymphoblastic leukaemia from 1983 to 1996, 25 received the vaccine and seroconversion was obtained in 76% after one dose and 92% after the second dose. Vaccine tolerance was adequate. The incidence of herpes zoster infection was decreased in vaccinated children during chemotherapy compared to the wild-virus infected ones. Nowadays that vaccine for healthy children is recommended, we consider a priority to protect from chickenpox the children affected by leukaemia that are in continuous complete remission of the disease.

Update on varicella vaccine

A live varicella vaccine has been licensed in Japan, Korea, some European countries, and the United States. Susceptible children can receive varicella vaccine at 12 to 18 months of age, and those who lack a reliable history of chickenpox should be immunized between 11 and 12 years of age. Susceptible children 13 years of age or older should receive two doses at least 1 month apart. Varicella vaccine administered under routine conditions has been proved to be highly effective. Varicella immunization has induced long-term humoral and cellular immunity. The varicella vaccine can be given in immunocompromized children, including children with leukemia and bone marrow transplantation recipients, when immune function recovers. Inactivated varicella vaccine can also reduce morbidity due to varicella zoster virus reactivation in high-risk populations.

The value of varicella vaccination in healthy children: cost-benefit analysis of the situation in France

The purpose of the cost-benefit analysis described in this article is to determine the economic value of vaccination of healthy children against varicella in France. It is based on the results of two specific investigations--an epidemiological model and a prospective observational study (1832 cases studied) of the socio-economic consequences of varicella. This cost-benefit analysis was conducted from the viewpoint of the society and that of the patient, for vaccination coverage rates ranging from 10 to 90%. This analysis demonstrates the value of varicella vaccination when associated with measles-mumps-rubella (MMR) vaccination: if varicella and MMR vaccines are co-administered, the vaccination of 80% of the children against varicella leads to a reduction in medical costs associated with varicella including that of vaccination, ranging from 10 to 77% according to the values adopted for vaccination costs, varicella treatment costs, discount rate and vaccine efficacy. The results of this study also underline the benefits of a vaccination policy that aims to achieve a high rate of coverage, thereby reaping the highest benefit from vaccination, and also avoiding potential negative consequences.

Comparison of primary sensitization of naive human T cells to varicella-zoster virus peptides by dendritic cells in vitro with responses elicited in vivo by varicella vaccination

Dendritic cells (DC) are potent APC during primary and secondary immune responses. The first objective of this study was to determine whether human DC mediate in vitro sensitization of naive CD4+ T cells to epitopes of the immediate early 62 (IE62) protein of varicella zoster virus (VZV). The induction of CD4+ T cell proliferative responses to eight synthetic peptides representing amino acid sequences of the VZV IE62 protein was assessed using T cells and DC from VZV-susceptible donors. The second objective was to compare in vitro responses of naive T cells with responses to VZV peptides induced in vivo after immunization with varicella vaccine. T cell proliferation was induced by three peptides, P1, P4, and P7, in 71-100% of the donors tested before and after vaccination using DC as APC. Monocytes were effective APC for VZV peptides only after immunization. Two peptides, P2 and P8, induced naive T cell proliferation less effectively and were also less immunogenic for T cells from vaccinated or naturally immune donors. T cell recognition of specific peptides was concordant between naive, DC-mediated responses, and postvaccine responses using monocytes as APC in 69% of comparisons (p = 0.05; chi2); the predictive value of a positive response to an IE62 peptide before immunization for T cell sensitization in vivo was 82%. These observations indicate that primary T cell responses detected in vitro using DC as APC may be useful to characterize the potential immunogenicity of viral protein epitopes in vivo.

Risk factors for breakthrough varicella in healthy children

AIM

To evaluate the risk factors for breakthrough varicella in a follow up study of a cohort of 181 healthy children immunised when aged 9-24 months with a reformulated Oka strain varicella vaccine (SmithKline Beecham Biologicals/Oka).

DESIGN

The children were randomised in a double blind manner into one of four groups to receive one of two production lot vaccine batches, at two different titres (high titre, 10(3.9) and 10(4.0) plaque forming units (pfu); low titre (heat exposed), 10(2.7) and 10(2.8) pfu). The overall seroconversion rate after immunisation was 99%.

RESULTS

One hundred and sixty-eight patients were available for review after a mean (SD) follow up of 35 (9) months after vaccination. Multivariate analysis indicated that risk factors for breakthrough varicella were household contact with varicella (adjusted odds ratio (OR), 19.89; 95% confidence interval (CI), 18.39 to 21.39), vaccination age of < or = 14 months (adjusted OR, 2.30; 95% CI, 1.69 to 2.90), and receiving low titre (10(2.7) pfu) vaccine (adjusted OR, 2.13; 95% CI, 1.54 to 2.73). All children who developed breakthrough varicella, had a modified varicella illness, except for three, all of whom had received low titre vaccine.

CONCLUSION

The identification of young immunisation age (< or = 14 months) and low titre vaccine as risk factors for breakthrough varicella have important implications for the implementation of varicella vaccination programmes in healthy children.

Use of a live attenuated varicella vaccine to boost varicella-specific immune responses in seropositive people 55 years of age and older: duration of booster effect

Varicella-zoster virus (VZV)-specific T cell immunity was measured in 130 persons > or = 55 years of age 6 years after they received a live attenuated VZV vaccine. Circulating T cells, which proliferated in vitro in response to VZV antigen, were enumerated (VZV responder cell frequency assay). Six years after the booster vaccination, the VZV-responding cell frequency (1/61,000 circulating cells) was still significantly (P < .05) improved over the baseline measurements (1/70,000) and appears to have diminished the expected decline in frequency as these vaccinees aged (to 1/86,000). Ten herpes-zoster--like clinical events were recorded. Although the frequency of these events, approximately 1/100 patient-years, is within the expected range of such events for this age cohort, the number of lesions was small, there was very little pain, and there was no postherpetic neuralgia. These results support the development of a vaccine to prevent or attenuate herpes zoster.

Safety, tolerability and immunogenicity of concomitant injections in separate locations of M-M-R II, VARIVAX and TETRAMUNE in healthy children vs. concomitant injections of M-M-R II and TETRAMUNE followed six weeks later by VARIVAX

OBJECTIVES AND STUDY DESIGN

The primary objectives of this study were to compare immunologic responses, antibody persistence, safety and varicella breakthrough rates when VARIVAX (varicella vaccine) is given at the same time as M-M-R II (measles, mumps, rubella vaccine) and TETRAMUNE (conjugate Haemophilus influenzae type b, diphtheria, tetanus and whole cell pertussis vaccine) at separate injection sites (Group A) vs. VARIVAX given 6 weeks after M-M-R II and TETRAMUNE (Group B). Six hundred nine healthy children, 12 to 23 months of age, were randomized to one of two treatment (immunization) groups (Group A and Group B). Blood for antibody titers was drawn on the day of immunization, 6 weeks after each injection and 1 year later. Local and systemic adverse reactions were recorded. Exposure and cases of varicella were documented through a 1-year follow-up period.

RESULTS

Measles, mumps and rubella seroconversion rates and geometric mean titers (GMTs) were similar for both treatment groups. Varicella seroconversion rates were also similar between groups. However, varicella GMTs and percent with a varicella-protective level [> or =5.0 glycoprotein (gp) enzyme-linked immunosorbent assay (ELISA) units] did not meet the prespecified criteria for similarity were lower for Group A (GMT 10.5; 82.8% > or =5.0 gp ELISA units) than for Group B (GMT 14.5; 91.2% > or =5.0 gp ELISA units). The GMTs between groups for other antibodies were similar. At the 1-year follow-up antibody titers were comparable in both groups and breakthrough varicella cases appeared generally similar. There were fewer local adverse events (AEs) at the VARIVAX injection sites (9.8% and 2.9%, Group A and B, respectively) than at the TETRAMUNE sites (27.9% and 24.0%). Systemic AEs were not statistically different when M-M-R II was administered alone (8.6%) or concomitantly with VARIVAX (8.9%). When VARIVAX was given alone AEs were 1.8%. The rate of fever > or =102 degrees F after M-M-R II and TETRAMUNE administered together was 10.7% on Days 0 to 3 and 23.7% on Days 7 to 21. When VARIVAX was administered alone, the rate of fever was 5.4% on Days 0 to 3 (P = 0.018) and 10.8% on Days 7 to 21 (P<0.001).

CONCLUSION

Because the varicella titers were comparable and varicella breakthrough rates generally similar at 1 year in both groups, we expect that the concomitant administration of VARIVAX with M-M-R II and TETRAMUNE has clinical effectiveness similar to that with VARIVAX 6 weeks after the administration of these other two vaccines. VARIVAX appears to be less reactogenic than M-M-R II and TETRAMUNE.