Research and analysis

HPR volume 12 issue 25: news (13 July)

Updated 21 December 2018

Updated guidance on use of varicella zoster immunoglobulin (VZIG)

Chickenpox is a common and generally mild childhood illness, although infection in immunosuppressed individuals, neonates and pregnant women can result in severe and even life -threatening disease. To prevent severe infection in these at-risk individuals, varicella zoster immunoglobulin (VZIG) is recommended according to national guidelines [1]; this guidance has been temporarily modified in response to VZIG supply shortages (see below).

The rationale for offering prophylaxis to at-risk groups is to reduce both the force of the disease and the risk of complications such as pneumonitis, rather than to prevent infection. Chickenpox in pregnancy can lead to complications for both the mother and her baby, depending on the timing of infection. During the first 20 weeks of pregnancy there is a risk of fetal varicella syndrome occurring; from 20 weeks, the greatest risk is of maternal complications including pneumonia. [2]

The use of VZIG in pregnant women is therefore two-fold: reducing severity of maternal infection and potential reduction in the risk of fetal infection. Maternal chickenpox can still occur despite VZIG prophylaxis and therefore it is important that women are informed to seek prompt treatment (with aciclovir) if they develop a rash. Current guidance recommends VZIG (4 vials; 1000mg) for susceptible pregnant women at any stage of pregnancy, provided it can be administered within 10 days of contact.

Varicella zoster immunoglobulin is a scarce blood product that is centrally procured and issued by Public Health England. Restrictions have been placed on VZIG use in pregnant women in the past when supplies have been short. As of 6 July 2018 – as a result of a significant shortage of supply due to manufacturing issues – VZIG will only be issued to susceptible pregnant women who have had a significant exposure to chickenpox/shingles in the first 20 weeks of pregnancy. This urgent advice has been considered and agreed between PHE experts and the chair of the JCVI varicella subcommittee. The subcommittee also advised that, based on extensive safety evidence, pregnant women who are exposed after 20 weeks, should be offered the oral anti-viral drug, aciclovir (800mg 4 times a day from day 7 to 14).

As oral aciclovir is not licensed for use in pregnancy, prescribing for pregnant women would constitute ‘off-label’ use. Clinicians are able to prescribe medicines outside the terms of the licence (meaning ‘off-label’) when this is in the best interests of the patient on the basis of available evidence. Further advice on off-label prescribing is on the MHRA website. [3]

Recommendations for VZIG for immunosuppressed contacts and neonates remain unchanged and risk assessment should proceed according to the national guidelines. [1]

References

1. PHE website. Immunoglobulin: when to use - guidance for issuing varicella zoster immunoglobulin (2017).
2. PHE website. Immunisation against infectious disease (the ‘Green Book’). Chapter 34: varicella.
3. MHRA website. Off-label unlicensed use of medicines: prescribers’ responsibilities - prescribing in a patient’s best interests.

Infection reports in this issue

• Laboratory surveillance of Proteus, Morganella and Providencia species bacteraemia in England, Wales and Northern Ireland: 2017