An Outbreak of Varicella among children attending preschool and elementary school in Illinois

In our investigation of a varicella outbreak among students in preschool, kindergarten, and grades 1-3 in Winnebago County, Illinois, we found an overall varicella vaccine efficacy of 88%, evidence that the circulating virus was a wild-type strain (as determined by polymerase chain reaction analysis), and evidence that vaccination of children </=15 months of age was associated with an increased risk for breakthrough varicella (relative risk, 3.7; 95% confidence interval, 1.1-13.1; P=.04). The efficacy of varicella vaccine might be improved if administration of the initial vaccine dose is delayed until children are >/=15 months of age.

Younger age at vaccination may increase risk of varicella vaccine failure

To determine vaccine effectiveness (VE), a varicella outbreak in a highly vaccinated day-care center (DCC) population in Pennsylvania was investigated. In Pennsylvania, proof of immunity is required for children >or=12 months old for DCC enrollment. Questionnaires were administered to parents of children who had attended the DCC continuously during the study period (1 November 1999-9 April 2000) to determine history of varicella disease or vaccination and for information about any recent rash illnesses. VE was calculated for children >or=12 months old without a history of varicella. There were 41 cases of varicella among 131 attendees, with 14 cases (34%) among vaccinated children. VE was 79% against all varicella and 95% against moderate or severe varicella. Vaccination at <14 months was associated with an increased risk of breakthrough disease (relative risk, 3.0; 95% confidence interval, 0.9-9.9). Despite varicella vaccination coverage of 80%, a sizeable outbreak occurred. Early age at vaccination may increase the risk of vaccine failure.

Using stated preference discrete choice modelling to evaluate the introduction of varicella vaccination

Applications of stated preference discrete choice modelling (SPDCM) in health economics have been used to estimate consumer willingness to pay and to broaden the range of consequences considered in economic evaluation. This paper demonstrates how SPDCM can be used to predict participation rates, using the case of varicella (chickenpox) vaccination. Varicella vaccination may be cost effective compared to other public health programs, but this conclusion is sensitive to the proportion of the target population immunised. A choice experiment was conducted on a sample of Australian parents to predict uptake across a range of hypothetical programs. Immunisation rates would be increased by providing immunisation at no cost, by requiring it for school entry, by increasing immunisation rates in the community and decreasing the incidence of mild and severe side effects. There were two significant interactions; price modified the effect of both support from authorities and severe side effects. Country of birth was the only significant demographic characteristic. Depending on aspects of the immunisation program, the immunisation rates of children with Australian-born parents varied from 9% to 99% while for the children with parents born outside Australia they varied from 40% to 99%. This demonstrates how SPDCM can be used to understand the levels of attributes that will induce a change in the decision to immunise, the modification of the effect of one attribute by another, and subgroups in the population. Such insights can contribute to the optimal design and targeting of health programs.

Guidelines for preventing opportunistic infections among HIV-infected persons--2002. Recommendations of the U.S. Public Health Service and the Infectious Diseases Society of America

In 1995, the U.S. Public Health Service (USPHS) and the Infectious Diseases Society of America (IDSA) developed guidelines for preventing opportunistic infections (OIs) among persons infected with human immunodeficiency virus (HIV); these guidelines were updated in 1997 and 1999. This fourth edition of the guidelines, made available on the Internet in 2001, is intended for clinicians and other health-care providers who care for HIV-infected persons. The goal of these guidelines is to provide evidence-based guidelines for preventing OIs among HIV-infected adults and adolescents, including pregnant women, and HIV-exposed or infected children. Nineteen OIs, or groups of OIs, are addressed, and recommendations are included for preventing exposure to opportunistic pathogens, preventing first episodes of disease by chemoprophylaxis or vaccination (primary prophylaxis), and preventing disease recurrence (secondary prophylaxis). Major changes since the last edition of the guidelines include 1) updated recommendations for discontinuing primary and secondary OI prophylaxis among persons whose CD4+ T lymphocyte counts have increased in response to antiretroviral therapy; 2) emphasis on screening all HIV-infected persons for infection with hepatitis C virus; 3) new information regarding transmission of human herpesvirus 8 infection; 4) new information regarding drug interactions, chiefly related to rifamycins and antiretroviral drugs; and 5) revised recommendations for immunizing HIV-infected adults and adolescents and HIV-exposed or infected children.

Second varicella infections: are they more common than previously thought?

OBJECTIVE

To describe the epidemiology and clinical characteristics of varicella reinfections reported to a surveillance project.

METHODS

We investigated varicella cases reported to a surveillance project between January 1, 1995, and December 31, 1999--with more extensive investigation of cases reporting previous varicella with onset between January 1, 1998, and September 30, 1998--to provide a more detailed description of first and second varicella infections. A simple decision tree was used to assess the likelihood that reported first and second infections were varicella.

RESULTS

Among varicella cases reported to the surveillance project, 4.5% of cases in 1995 and 13.3% of cases in 1999 reported previous varicella. More than 95% of first infections were physician diagnosed, epidemiologically linked to another case, or had a rash description consistent with varicella; the same was true for reported second infections. People who reported reinfections were generally healthy. There was a family history of repeat infections in 45% of people who reported reinfections.

CONCLUSIONS

Clinical varicella reinfections may occur more commonly than previously thought. Additional studies of the predictive value of a positive varicella history and laboratory studies of reported reinfections are indicated to guide varicella vaccination policy.

Vaccination with measles, mumps and rubella vaccine and varicella vaccine: safety, tolerability, immunogenicity, persistence of antibody and duration of protection against varicella in healthy children

BACKGROUND

Administration of M-M-R II (Measles, Mumps and Rubella Virus Vaccine, Live) and VARIVAX [Varicella Virus Vaccine Live (Oka/Merck)] given concomitantly at separate injection sites during the same office visit could increase vaccine compliance by reducing the number of health care visits for immunizations. We compared the safety and immunogenicity of M-M-R II and VARIVAX given concomitantly at separate sites (Group A) with administration of the two vaccines 6 weeks apart (Group B) as well as the persistence of varicella antibody and the duration of protection afforded by varicella vaccine.

METHODS

A total of 603 healthy children, ages 12 months to 6 years, with no history of measles, mumps, rubella, varicella and zoster or vaccination against these diseases, were randomized to either Group A or B and were followed for clinical reactions and serologic responses to all four viral components. Children were enrolled from August through December, 1993. Subjects were followed for 5 years to evaluate persistence of varicella antibody and breakthrough varicella rates. We compared breakthrough rates to expected attack rates in unvaccinated children to produce estimates of vaccine efficacy.

RESULTS

Both vaccine regimens were generally well-tolerated. There were no significant differences between the groups in the rates of fever, injection site reactions or rashes after vaccination. Seroconversion rates and geometric mean titers for measles, mumps and rubella were not significantly different between groups. The varicella seroconversion rate and percentage with glycoprotein-based ELISA titers > or = 5.0 units were similar between the two groups (99.5 and 92.5% vs. 100 and 94.8% for Groups A and B, respectively), but the geometric mean titers were statistically significantly different (13.2 for Group A and 17.9 for Group B). Varicella antibody persistence rates were >98 to 100% during 6 years of follow-up in both groups. Compared with historical rates, varicella vaccine efficacy during 5 years was estimated to be 90.5% (95% confidence interval, 86.2%, 95.0%) and 88.9% (95% confidence interval, 83.7%, 93.7%) in Groups A and B, respectively.

CONCLUSIONS

Administration of M-M-R II and VARIVAX concomitantly at separate injection sites or 6 weeks apart was generally well-tolerated and immunogenic in healthy children 12 months to 6 years of age. VARIVAX administered with M-M-R II induced persistent immunity and long-term protection against breakthrough varicella infection.

The effect of vaccination on the epidemiology of varicella zoster virus

Varicella zoster virus (VZV) causes chickenpox (varicella) on primary exposure and can reactivate later in life to cause shingles (zoster). As primary infection is more serious in adults than children, and exposure to the virus might boost the immune response to both chickenpox and shingles, there are two main concerns regarding infant VZV vaccination: that it could lead to an increase in adult disease; and/or that it could lead to a temporary increase in the incidence of shingles. This paper reviews the evidence for such outcomes. The consensus view of mathematical modelling studies is that the overall varicella associated burden is likely to decrease in the long term, regardless of the level of vaccine coverage. On the other hand, recent evidence suggests that an increase in zoster incidence appears likely, and the more effective vaccination is at preventing varicella, the larger the increase in zoster incidence. Targeted vaccination of susceptible adolescents and/or the contacts of high-risk individuals can be effective at preventing disease in these individuals with minimal risk to the community. However, targeted strategies would not prevent most disease (including most severe disease), and will not lead to a long-term reduction in the incidence of zoster. Understanding the mechanisms for maintaining immunity against varicella and zoster is critical for predicting the long-term effects of vaccination. Meanwhile sensitive surveillance of both chickenpox and shingles is essential in countries that have implemented, or are about to implement, varicella vaccination.

Varicella: a vaccine preventable disease?

OBJECTIVES

To present a review of varicella disease, vaccine development and implementation of universal vaccination, discuss common questions about the vaccine and the epidemiology of the disease since licensure of the varicella vaccine.

METHODS

Review the incidence of complications from varicella disease prior to vaccine licensure, safety of the varicella vaccine from clinical trials and post-marketing surveillance data, the impact of the vaccine on disease incidence where high vaccine coverage has been achieved, and address some barriers to vaccination. Raise issues that developed since 1995.

RESULTS

The safety data gathered during the 20-year-gestation period of this vaccine prior to licensure has been confirmed. The vaccine works-in areas where vaccine coverage is over 70%, there has been a decline in disease, most marked in the age group with the best vaccine coverage (the 1-4-year olds), leading to a concern that unexposed susceptible children may reach adulthood and remain susceptible unless better practice of universal vaccination of ALL susceptible is practiced.

CONCLUSIONS

Varicella disease has declined in areas with moderate vaccine coverage. Continued implementation of existing vaccine policies will lead to further reductions of varicella morbidity and mortality throughout the USA.

Varicella vaccination in pediatric kidney transplant candidates

Existing studies support the use of varicella vaccine in a two-dose regimen in patients with renal disease prior to transplantation. Levels of anti-varicella zoster virus antibody should be monitored on a regular basis after immunization, and where a loss of a previously protective antibody titer occurs, a third booster dose should be considered pretransplant. Further data need to be collected regarding the use of the vaccine in seronegative patients who have already undergone transplantation.

Clinical manifestations of varicella-zoster virus infection

Infections by VZV, the virus that causes chickenpox and herpes zoster, usually are diagnosed by the classic clinical presentations. In immunocompromised patients, however, the atypical presentation can make the diagnosis more challenging. Although varicella typically follows an uncomplicated course in children, adults and immunocompromised patients can develop complications involving several organs; some complications may be fatal. Prevention of disease with the vaccine is ideal. When varicella or zoster infection does occur, proper treatment should be initiated, depending on the age and immune status of the patient.

1: Infections in pregnant women

Some infections are more serious in pregnant than non-pregnant women because of the potential for vertical transmission to the fetus or infant (eg, varicella, rubella, cytomegalovirus infection, toxoplasmosis and listeriosis). Pre-pregnancy or routine antenatal screening for presence of, or susceptibility to, some of these infections and appropriate management can prevent adverse fetal or perinatal outcomes; screening should include rubella IgG, hepatitis B surface antigen, serological tests for syphilis and HIV antibody. If certain other vertically transmissible infections are suspected because of a positive antenatal test result, confirmatory tests for maternal and, if indicated, fetal infection are essential before intervention is considered (eg, cytomegalovirus infection). For some vertically transmissible infections that are not readily preventable, appropriate management of maternal infection can reduce fetal damage (eg, toxoplasmosis).