The supply of VZIG is limited by the availability of suitable donors and its use is restricted to those at greatest risk and for whom there is evidence that it is likely to be effective.
VZIG prophylaxis is recommended for individuals who fulfil all of the following three criteria:
1.Significant exposure to chickenpox or herpes zoster
2.A clinical condition that increases the risk of severe varicella; this includes immunosuppressed patients, neonates and pregnant women
3.No antibodies to VZ virus
Definition of a significant exposure to VZ virus:
1. Type of VZ infection in the index case:
the risk of acquiring infection from an immunocompetent individual with non-exposed zoster lesions (e.g. thoracolumbar (the trunk)) is remote. The issue of VZIG should be restricted to those in contact with chickenpox, or those in contact with the following:
a) disseminated zoster
b) immunocompetent individuals with exposed lesions (e.g.ophthalmic zoster)
c) immunosuppressed patients with localised zoster on any part of the body (in whom viral shedding may be greater).
2. The timing of the exposure in relation to onset of rash in the index case:
VZIG should normally be restricted to patients exposed to a case of chickenpox or disseminated zoster between 48 hours before onset of rash until crusting of lesions, or day of onset of rash until crusting for those exposed to localised zoster.
3. Closeness and duration of contact:
The following should be used as a guide to the type of exposure, other than maternal/neonatal and continuous home contact, that requires VZIG prophylaxis:
a) contact in the same room (e.g. in a house or classroom or a two- to four-bed hospital bay) for a significant period of time (15 minutes or more).
b) face-to-face contact, e.g. while having a conversation
c) in the case of large open wards, airborne transmission at a distance has occasionally been reported and giving VZIG to all susceptible high-risk contacts should be considered (particularly in paediatric wards where the degree of contact may be difficult to define).
•Pregnant contacts with a positive history of chickenpox do not require VZV IgG testing if they were raised in the UK (90% of adults raised in the UK are immune).
•VZIG administration should not be delayed past seven days after initial contact while an antibody test is done.
Varicella zoster immunoglobulin (VZIG)
0–5 years: 250mg (one vial)
6–10 years: 500mg (two vials)
11–14 years: 750mg (three vials)
15 years or over: 1000mg (four vials)
If a second exposure occurs after three weeks, a further dose is required.
Contacts with bleeding disorders who cannot be given an intramuscular injection should be given intravenous normal immunoglobulin at a dose of 0.2g per kg body weight (i.e. 4ml/kg for a 5% solution) instead. This will produce serum VZ antibody levels equivalent to those achieved with VZIG.