Varicella in maternity units

Neonatal antibody titers against varicella-zoster virus in relation to gestational age, birth weight, and maternal titer

OBJECTIVE

Varicella-zoster virus (VZV) can cause severe disease in premature neonates. The fetus receives protective maternal VZV-immunoglobulin G (IgG) mainly in the third trimester of pregnancy. Therefore, premature neonates are considered at risk for VZV infection. Administration of varicella-zoster immunoglobulin (VZIG) within 96 hours after exposure effectively prevents severe illness in susceptible patients. The objectives of this study were to define the major determinants of the neonatal VZV-IgG titer and to determine the half-life of transplacentally acquired VZV-IgG. Guidelines provided by the Centers for Disease Control and Prevention for the use of VZIG in (premature) neonates were evaluated.

METHODS

VZV-IgG titers were measured in sera of 221 neonates and 43 mothers using a quantitative enzyme-linked immunosorbent assay. In 27 neonates, VZV-IgG titers were followed for up to 14 weeks.

RESULTS

In a linear regression model, the maternal antibody titer was the major determinant of the neonatal titer (beta = 0.89); gestational age was only of minor importance (beta = 0.18). The median half-life of VZV-IgG in neonates was 25.5 days (range: 14.6-76.0 days). In the first weeks of life, major fluctuations of the VZV-IgG titer occurred in >50% of the neonates. The predictive value of Centers for Disease Control and Prevention guidelines for identification of neonates who should receive VZIG in case of exposure to VZV was poor: positive and negative predictive values were 0.80 and 0.43, respectively.

CONCLUSIONS

The neonatal VZV-IgG titer is predominantly predicted by the maternal VZV-IgG titer, whereas birth weight and gestational age are much less predictive than previously reported.

An analysis of infection control of varicella-zoster virus infections in Addenbrooke's Hospital Cambridge over a 5-year period, 1987-92

This prospective study analyses infections with varicella-zoster virus (VZV) in Addenbrooke's Hospital, Cambridge during 1987-92 and examines the spread of infection. In total, 93 patients and staff experienced VZV infection. Twenty-one patients had varicella and 49 experienced zoster. None of 101 patients and 1 of 625 staff members in contact with varicella cases acquired infection. By contrast, 2 of 227 patients, and 5 of 1039 staff in contact with zoster cases acquired varicella. One out of 28 (3.6%) VZV antibody-negative patients and staff in contact with varicella acquired infection, compared with 5 out of 29 (17.2%) VZV antibody-negative patients and staff in contact with zoster. Thus, zoster was found to be a more frequent cause of nosocomial infection than varicella. Fourteen members of staff had VZV infection during the study period. One of 99 patients and none of 389 staff members in contact with these cases developed varicella. The cost of dealing with infection control for VZV infections in our hospital is estimated to be Pounds 714 per patient case and a total of Pounds 13,204 per year.