5 years of Varicella zoster immunoglobulin (VZIG) use in a regional issuing centre: If prevention is better than a cure, are we using the best strategy in the era of vaccination?

Background: VZIG, given post exposure to susceptible high risk patients, is expensive, gives short term protection and has 50% failure. Imported from the US, the donor pool and stocks may fall with VZ vaccine use. Preventing exposure is advised yet infectivity starts pre-rash. Therefore other measures to prevent exposure in high risk patients should be considered. In the UK, VZ Oka vaccine is available for susceptible health workers and household contacts of immunosuppressed. Options include childhood immunisation (reducing infections and likely exposures), antenatal screening with postnatal vaccine, or screening/ vaccination of female teachers/ nursery workers to lower occupational risk (both reducing adult VZ infection and exposure in pregnancy). Sheffield Virology Department is a UK issuing centre for VZIG; this study was done to understand the circumstances leading to VZIG use in our population in order to lower exposures.

Methods: Data was retrospectively analysed on VZIG issues from 01/01/11 to 31/12/15 alongside laboratory data on tests pre/post exposure.

Results: 242 issues were reviewed: Most were pregnant women (68%) and exposure to chickenpox (93%). 14/20 premature babies were exposed by siblings; 11 by that of a different baby. 10/34 babies were exposed to maternal VZ around birth. Mean time to VZIG issue ranged from 1.9 in <7 day olds to 5.1 in pregnancy. There were 8 lab-reported cases of infection <28 days from VZIG (7 in pregnancy, 1 immunosuppressed), 1 at 35 days, and 2 asymptomatic seroconversions. Of the 9 cases, 8 were household exposures, VZ IgG levels pre-exposure in 7 were <30 iU/ml, and mean time to VZIG 5.8 days. 31 exposures were preventable by current guidance, 31% from failure to vaccinate household members. 75.6% of exposures were to a child. 51% of pregnant women could have been screened/ vaccinated after a previous pregnancy; 1 had VZ infection in her next pregnancy. 5.4% of cases were teachers/ nursery workers.

Conclusion: This work confirms that although many exposures are preventable by current guidance, most VZ exposures are from children and unavoidable. With many reasons to consider alternative methods of protection, this data supports the debate of wider vaccination use, especially in children, to protect a vulnerable cohort.