Antiviral agents for treatment of herpes simplex virus infection in neonates

Herpes simplex virus (HSV) is a rare but serious neonatal pathogen. Prior to the availability of antiviral drugs the mortality associated with all but localised neonatal infection was high, with 85% of infants with disseminated HSV infection and 50% of infants with encephalitis dying by one year of age. The morbidity in the survivors of multiorgan infection was also high, with up to 50% experiencing long-term neurological sequelae.

To determine the effect of antiviral agents in the treatment of neonatal HSV infections on mortality, progression of disease and neurodevelopmental sequelae at approximately one year. The secondary objective was to assess the effect of antiviral agents on major complications associated with the use of these agents including nephrotoxicity and bone marrow suppression.

Trials were identified by searching the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 4, 2008), MEDLINE (1996 - Nov 2008), EMBASE (1982 - Nov 2008) and reference lists of published trials.

Randomised and quasi-randomised controlled trials of antiviral therapy in infants less than one month of age with virologically proven HSV infection were included.

Data were extracted and the analyses performed independently by two review authors. Studies were analysed for methodological quality using the criteria of the Cochrane Neonatal Review Group. All data were analysed using RevMan 5.1. When possible, meta-analysis was performed to calculate typical relative risk, typical risk difference, along with their 95% confidence intervals (CI).

Two eligible studies of a total of 273 infants were included. Both studies were randomized controlled trials. One study treated 63 infants with vidarabine or placebo (Whitley 1980) and the other study treated 210 infants with aciclovir or vidarabine (Whitley 1991).In the study comparing vidarabine with placebo (Whitley 1980), infants with all forms of neonatal HSV disease were included [disseminated disease, central nervous system (CNS) disease alone, and skin, eye and mouth (SEM) disease].There was no significant reduction in the risk of mortality when analyzed as an entire group; however, mortality was significantly reduced when data from infants with CNS disease or disseminated disease were combined. There was no difference in the rate of neurological abnormalities in survivors at one year when analyzed as an entire group or by disease category.There was no difference between aciclovir and vidarabine (Whitley 1991) in preventing mortality from neonatal HSV disease, in preventing disease progression, in reducing the incidence of neurological abnormality at one year, or in the incidence of drug-induced renal or bone marrow toxicity. In infants with SEM disease, there was no significant difference in neurological outcome with aciclovir compared vidarabine treatment. Both drugs were well tolerated in the newborn period.

There is insufficient trial evidence to evaluate the effects of antiviral agents with controls or with each other. The rarity of the condition makes effectively powered clinical trials difficult to perform. The efficacy of newer antiviral agents with better bioavailability (e.g. valaciclovir, valganciclovir) for the treatment of neonatal disease needs to be evaluated in randomised trials. The efficacy of oral formulations need to be evaluated as they may be useful for infants with skin, eye or mouth HSV disease or in the treatment of infants with recurrences after the neonatal period.