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.