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

Global impact of varicella vaccination programs

Although varicella is usually a mild and self-limited disease, complications can occur. In 1998, the World Health Organization recommended varicella vaccination for countries where the disease has a significant public health burden. Nonetheless, concerns about a shift in the disease to older groups, an increase in herpes zoster in the elderly and cost-effectiveness led many countries to postpone universal varicella vaccine introduction. In this review, we summarize the accumulating evidence, available mostly from high and middle-income countries supporting a high impact of universal vaccination in reductions of the incidence of the disease and hospitalizations and its cost-effectiveness. We have also observed the effect of herd immunity and noted that there is no definitive and consistent association between vaccination and the increase in herpes zoster incidence in the elderly.

Reintroducing OPV in Israel on the journey to global polio eradication - Estimation at a low rate of contraindicated population

INTRODUCTION

The 2013 reemergence of wild poliovirus in Israel led to the reinstatement of a routine OPV vaccination. Fearing VAPP in immunocompromised, the MOH regulated contraindications for vaccination candidates and household contacts. In this study we estimate the size of the contraindicated population to OPV vaccination.

METHOD

We studied vaccination candidates aged 2-9 and 14-23 months and probable household contacts. Using the rate of contraindications extracted for each study group from a medical records database, a statistical model was built to estimate the probability of contraindications in candidates.

RESULTS

3.9% of the 2-9-month-old study group and 4% of the 14-23-month-old group had contraindications by either self or household contacts.

CONCLUSION

A statistical model can provide an estimation of the contraindicated population and can be used in the future when devising vaccination campaigns. In contrast to concerns raised by the MOH, our findings show a smaller than anticipated contraindicated population.

Single-dose varicella vaccine effectiveness in school settings in China

BACKGROUND

Varicella vaccine has been available in the private sector in China for a decade as a single-dose regimen, but varicella vaccine effectiveness (VE) has not been fully examined in school settings yet.

METHODS

A matched case-control study was carried out in elementary schools and daycares in Tai'an prefecture, Shandong province, China. Clinical diagnosis of varicella and breakthrough disease was used for this study. Four controls were randomly selected from classmates; two from classmates of the case and two from another class of the same grade without cases. Vaccination status, date of vaccination, and vaccine product received if vaccinated were collected from home and clinic immunization records. Vaccination status of all students in schools/daycares with varicella cases from home immunization records or parental recall was used to calculate vaccination coverage.

RESULTS

The overall varicella VE was 83.4% (95% confidence interval 71.4-90.3%). Receipt of varicella vaccine five years or more years before the outbreak was significantly associated with breakthrough varicella (odds ratio=4.7, P<0.001), while age at vaccination (<15 vs. ≥15 months) was not (odds ratio=1.5, P=0.62). Varicella vaccination coverage was 41% with substantial variation across schools (range of 0-93.8%).

CONCLUSIONS

Single-dose varicella vaccine is highly effective in school settings. Maintaining limited vaccination coverage might shift varicella disease burden to older individuals, who are more prone to develop severe outcomes if varicella occurs.

Optimizing immunization in pediatric special risk groups

This article analyzes the current recommended practices and evidence in the immunization of pediatric 'special risk groups'. Special risk group patients are at higher risk of vaccine-preventable diseases and hence require additional strategies to maximize protection against these diseases. The special risk groups include those with an underlying chronic disease, some of whom are on immunosuppressive therapy to treat that condition. The article uses four special risk groups (acute lymphoblastic leukemia; preterm birth; juvenile idiopathic arthritis; and inflammatory bowel disease), to highlight the management considerations and potential vaccination strategies. The risks, benefits and timing of vaccination in the setting of immunosuppression require detailed discussion with treating clinicians, in particular the use of live-attenuated vaccines. The immunogenicity of vaccines in these special risk groups helps provide the evidence base for their immunization guidelines. Protection can include 'cocooning' (i.e., ensuring appropriate immunizations within the immediate family; e.g., varicella, influenza and pertussis vaccination). Improving timeliness and minimizing missed opportunities to vaccinate individuals with these special risk conditions will also optimize protection from vaccine-preventable diseases.

The effectiveness of varicella vaccine in China

BACKGROUND

The attenuated live varicella vaccine had been shown to be effective in preventing varicella and reducing the disease burden in the United States. However, little work has been done on investigating vaccine effectiveness in China where 3 varicella vaccines are available. Although the vaccines contain the same strain of virus, the vaccines licensed in China were from manufacturers different from the one licensed in the United States. We conducted a matched case-control study to assess the effectiveness of the 3 varicella vaccines in use in China.

METHODS

In 2005, we enrolled 1000 cases from Guangzhou, China and 1000 controls matched by age and place of residence. The cases were children clinically diagnosed with acute onset of a diffuse maculopapulovesicular rash without other apparent cause. We interviewed the legal guardians of the participants for demographic information and disease history after obtaining informed consent. We collected information on vaccination status from electronic vaccination records.

RESULTS

The 3 varicella vaccines in China (Varilrix from GlaxoSmithKline, Changchun and Shanghai from Changchun and Shanghai Institutes of Biologic Products, respectively) had similar effectiveness: Varilrix 86.4% (95% confidence interval [CI]: 72.6, 93.2), Changchun 79.5% (95% CI: 58.1, 90.0), and Shanghai 92.6% (95% CI: 68.9, 98.2). Vaccine effectiveness was higher during the first year after vaccination than during the subsequent 5 years, but the differences did not reach statistical significance.

CONCLUSIONS

The varicella vaccines in China are highly effective in preventing clinical varicella. Further studies on laboratory-confirmed cases are needed to verify the change of vaccine-induced immunity over time.

Varicella vaccination in pediatric kidney and liver transplantation

Reports about efficacy and safety of live-virus attenuated vaccines in patients before and after transplantation are mainly based on small patient numbers, making general recommendations for this patient population difficult. Children and adults as well as their close relatives and contact persons should be preferably immune to VZV before solid organ transplantation to avoid VZV-associated complications, thus making VZV vaccination necessary in susceptible individuals. The following literature review focused on efficacy and safety of VZV vaccination in pediatric kidney and liver transplant recipients. Review of literature also revealed that in all pediatric transplant candidates, humoral and cellular immunity against VZV should be consistently monitored to assess waning immunity under immunosuppressive treatment. This approach is desirable to estimate the risk of severe varicella disease after exposure in these patients.

Chickenpox in varicella IgG positive patients: experience of a regional paediatric oncology centre

Aciclovir prophylaxis was previously given to all immunocompromised patients treated by our unit, following contact with varicella zoster. In 2003, we changed practice according to National Guidelines, giving prophylaxis only to patients without serum varicella zoster immunoglobulin G antibody (VZ IgG) at diagnosis of their malignancy. Since then we have seen nine patients with acute lymphoblastic leukaemia (ALL) and VZ IgG positivity at diagnosis of their malignancy develop chickenpox. Our observations question current practice for patients with ALL.

Varicella vaccination of immunocompromised children

BACKGROUND

Exposure of immunocompromised children to varicella often requires postexposure prophylaxis. Exposures requiring this management are often not recognized. Varicella can be a severe disease when it occurs in immunocompromised children, in spite of antiviral therapy. Varicella exposure and varicella in these children can also disrupt scheduled therapy for their underlying illness. Both postexposure prophylaxis and treatment of varicella are likely to be expensive and use significant medical resources. Numerous trials have been undertaken to vaccinate children who are immunocompromised by a variety of conditions and therapies that depress their immune function.

METHODS

Clinical trials of varicella vaccine administration to immunocompromised children that were reported since 1975 were identified in the Ovid medical database. Reports were selected for analysis and discussion on the basis of their completeness and the utility of their conclusions.

RESULTS

Vaccination before immune compromise is discussed as a strategy for some settings. The obstacles, potential opportunities, and success in varicella vaccination for immunocompromised children are separately analyzed for (1) children with leukemia and other malignancies, (2) human immunodeficiency virus-infected children, and (3) children with hematopoietic stem cell or solid-organ transplantation.

CONCLUSIONS

Vaccination before immune compromise is often successful, and the vaccine-induced response is usually partially or fully protective. In many treatment settings, it is possible to safely vaccinate once the level of immune suppression has been reduced. Targets for future research are outlined. A consensus conference should be undertaken to develop guidelines for the use of varicella vaccine in immunocompromised children.

Review of the Varilrix varicella vaccine

Varicella zoster virus causes an acute infection that affects most children globally, but the age of infection can be greater in residents of tropical areas. It has generally been considered a mild disease, although there are accumulating data to show that it can cause significant morbidity and mortality in immunocompetent as well as immunocompromised children and adults. Oka-strain live attenuated varicella vaccines were developed in the 1970s. Varilrix developed by GlaxoSmithKline Biologicals (Rixensart, Belgium), is one of the vaccines produced and marketed in over 80 countries. Similar to the other Oka-strain vaccines, Varilrix is safe, immunogenic and efficacious in both immunocompromised and immunocompetent children and adults.

Risk of transmission associated with live attenuated vaccines given to healthy persons caring for or residing with an immunocompromised patient

OBJECTIVE

Persons who receive live attenuated vaccine may occasionally transmit the vaccine strain to others. The risk of such transmission is a concern, especially for persons who provide care to immunocompromised patients (ie, family and healthcare workers [HCWs]). Since the Advisory Committee on Immunization Practices released guidelines 10 years ago, several new live attenuated products have been introduced, and additional information on older vaccines has become available. To better define the risk of transmission associated with live vaccines, we reviewed the currently available literature.

RESULTS

A review of the medical literature revealed no major risk of transmission associated with any live attenuated vaccine. A theoretical risk continues to exist for the live attenuated intranasal influenza vaccine and the smallpox vaccine.

CONCLUSIONS

The available data support routine vaccination with live attenuated vaccines for all household contacts of immunocompromised patients and for HCWs caring for such patients. The benefit for immunocompromised patients of providing herd immunity against this group of potentially devastating pathogens outweighs the risk, if any, of secondary transmission.

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.

Immunization recommendations for adults with cancer

OBJECTIVE

To review the published literature on immunizing nonbone marrow transplant adult cancer patients, summarize the findings, and make recommendations for the use of vaccines in this population.

DATA SOURCE

A search of MEDLINE and CancerLit was conducted (1966-June 2001) to find English-language clinical studies and review articles pertaining to immunization, vaccines, and cancer in humans. Recommendations of the Advisory Committee on Immunization Practices were used extensively. References of each identified article were subsequently reviewed for additional relevant articles.

STUDY SELECTION AND DATA EXTRACTION

Representative epidemiologic reports, clinical trials, and recommendations of expert panels are summarized in this report. Relevant information was selected to describe the epidemiology of vaccine-preventable diseases, efficacy of the vaccines, and recommendations specific to adults with cancer.

DATA SYNTHESIS

In general, adults with cancer are at least at the same risk of infection with vaccine-preventable diseases as are healthy populations. Because of their compromised immune function, many patients who have undergone cancer treatment are specifically at increased risk of morbidity and mortality associated with measles and varicella infections. Asplenic patients with lymphoma are at increased risk of fulminant bacterial infections. Influenza infection is associated with significant morbidity in cancer patients. Although the protection conferred by immunization is lower in immunosuppressed patients with cancer, immunization with inactivated vaccines is indicated. Live vaccines should not be used except in very rare instances.

CONCLUSIONS

Immunization of adults with cancer is a critical component of their care. Although additional research is necessary, following established recommendations may protect individuals with malignancies from significant morbidity and mortality associated with vaccine-preventable diseases.