OBJECTIVES:

Economic evaluations of varicella vaccination typically consider only outpatient varicella cases. However, varicella complications can occur, requiring additional diagnostic procedures or hospitalizations. Therefore, their inclusion in such models should be considered. This systematic literature review aimed at identifying the prevalence and duration of complications, and case-fatality rates among patients with primary varicella.

METHODS:

Prospective and retrospective observational studies, reported worldwide in English between 1999–2020 were included. The search was performed in Medline and EMBASE. The following complications were assessed: bacterial skin infection, soft tissue infection, pneumonia, encephalitis, cerebellitis/acute cerebellar ataxia, meningitis, febrile seizure, hematological complications, gastroenteritis/diarrhea, dehydration, and systemic varicella complications.

RESULTS:

A total of 130 eligible studies were identified. Across studies, the proportion of patients who had developed some form of varicella complication ranged from 0.17% to 98.70% across studies. The most frequently reported complications were skin infection (0.17%–93.00%) and cerebellitis/acute cerebellar ataxia (0.01%–64.50%). Among the less common complications, the prevalence of lower respiratory tract infection was 0.02%–56.50%, encephalitis 0.01%–42.00%, systemic varicella complications 0.08%–50.00%, soft tissue infection (0.01%–60.00%),meningitis 0.00%–19.30%, gastroenteritis/diarrhea 1.43%-43.27%, febrile seizures 0.01%–20.00%, hematological complications 0.02%–45.12%, and dehydration 0.11%–32.80%. The symptoms associated with soft tissue infections lasted for up to 21 days whereas for pneumonia, hematological complications, and gastroenteritis, it lasted between up to 2 and 10 days. The fatality rate for the overall complications ranged from 0.16% to 6.0%. Results varied noticeably depending on whether the studied population comprised all varicella patients, or patients hospitalized with varicella complications.

CONCLUSIONS:

Varicella infection is associated with various complications that may be fatal. To capture the comprehensive burden of varicella and value of preventative measures like vaccination in economic evaluations, including the value of these complications is important in terms of cost and quality of life loss implications.