Vaccines for post-exposure prophylaxis against varicella (chickenpox) in children and adults
- Kristine Macartney1,*,
- Peter McIntyre2
Editorial Group: Cochrane Acute Respiratory Infections Group
Published Online: 16 JUL 2008
Assessed as up-to-date: 27 FEB 2008
DOI: 10.1002/14651858.CD001833.pub2
Copyright © 2008 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Database Title
- Abstract
- Article
- Tables
- References
- Other Versions
- Cited By
Abstract
Background
Live attenuated varicella vaccines for the prevention of varicella (chickenpox) has been demonstrated both in randomised controlled trials (RCTs) and in population-based immunisation programmes in countries such as the United States. However, many countries do not routinely immunise children against varicella, and exposures continue to occur. Although the disease is often mild, complications such as secondary bacterial infection, pneumonitis and encephalitis occur in about 1% of cases, usually leading to hospitalisation. The use of varicella vaccine in persons who have recently been exposed to the varicella zoster virus has been studied as a form of post-exposure prophylaxis (PEP).
Objectives
To assess the efficacy and safety of vaccines for use as PEP for the prevention of varicella in children and adults.
Search methods
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2008, Issue 1); MEDLINE (1966 to February 2008); and EMBASE (January 1990 to February 2008).
Selection criteria
RCTs and quasi-RCTs of varicella vaccine for PEP compared with placebo or no intervention. The outcome measures were efficacy in prevention of clinical cases and/or laboratory-confirmed clinical cases and adverse effects following vaccination.
Data collection and analysis
Two review authors independently extracted and analysed data using Review Manager software.
Main results
Three studies involving 110 healthy children who were siblings of household contacts were identified as suitable for inclusion. The studies varied in quality, study design, vaccine used, and outcomes measured and, as such, were not suitable for meta-analysis. Overall, 13 out of 56 vaccine recipients (18%) developed varicella compared with 42 out of 54 placebo (or no vaccine) recipients (78%). Of the vaccine recipients who developed varicella, the majority only had mild disease (with less than 50 skin lesions). In the three studies, most subjects received PEP within three days following exposure; too few subjects were vaccinated four to five days post exposure to ascertain the efficacy of vaccine given more than three days after exposure. No included studies reported on adverse events following immunisation.
Authors' conclusions
These small trials suggest varicella vaccine administered within three days to children following household contact with a varicella case reduces infection rates and severity of cases. No RCTs for adolescents or adults were identified. However safety was not adequately addressed.
Plain language summary
Post-exposure prophylaxis vaccine to prevent varicella (chickenpox)
This review assessed how useful the varicella (also known as chickenpox) vaccine is in preventing chickenpox when given to children or adults who have never been immunised or had chickenpox before, but who receive the vaccine within a short time following exposure to a person with chickenpox. Varicella is a highly contagious viral infection characterised by a widespread pustular rash, fever and generally feeling unwell.
Although many cases of chickenpox are mild, complications such as secondary bacterial infection, neurological complications, and other problems occur in at least 1% of cases, usually resulting in hospitalisation. The virus that causes chickenpox also remains dormant in sensory nerve roots after infection, and can reactivate later in life as a painful blistering rash known as herpes zoster or shingles.
Chickenpox can be prevented by vaccination with live attenuated varicella vaccine, however, many countries have not yet funded routine population-based immunisation programmes, and exposure to chickenpox remains commonplace.
The question of how to prevent chickenpox occurring in an adult or child who has been in contact with a person with the disease has led to trials of varicella vaccines in this setting. This review found that three separate trials support giving varicella vaccine to a child, particularly if given within three days of contact with a chickenpox case. Although in some cases, mild chickenpox may still occur, the vaccine is likely to prevent moderate to severe cases of chickenpox. The number of participants in these three trials was small and is a limitation of this review. There have been no trials of this type undertaken in adults, and none of the trials commented on adverse events following immunisation, such as fever or injection site symptoms.