Antivirals are now the recommended choice for all at-risk groups who have been exposed to chickenpox, including pregnant women, the UK Health Security Agency has said in updated guidance.
It follows temporary changes to guidance on antiviral use in some groups as an alternative to post-exposure prophylaxis (PEP) after significant shortages of varicella zoster immunoglobulin (VZIG) in 2018.
An expert working group has concluded that while the supply issue was resolved there have been ongoing global supply issues of a range of immunoglobulin products with supply interruptions remaining a potential risk.
This coupled with a review of safety and efficacy data on antivirals led the working group to conclude they should now be the choice for all at risk groups apart from susceptible neonates exposed within a week of delivery.
VZIG is still recommended for those in whom oral antivirals are contraindicated, the UKSHA guidelines said.
Those who are eligible include people who have had significant exposure to chickenpox or shingles during the infectious period and who are at increased risk because for example they are immunosuppressed or pregnant, and who have no antibodies to varicella-zoster virus.
The recommendations include details on timing of exposure, duration of contact and how to assess susceptibility.
In immunocompetent individuals including pregnant women, a history of previous chickenpox, shingles or two doses of varicella vaccine counts as evidence of immunity.
But without that history, urgent antibody testing should be undertaken on a recent blood sample, the guidelines recommend.
Oral aciclovir (or valaciclovir) is now the first choice of PEP for susceptible immunosuppressed individuals, all susceptible pregnant women at any stage of pregnancy and infants at high risk from day seven to 14 after exposure, the UKHSA said.
But the guidelines highlight that while recommended, the drugs are currently not licensed for this purpose.
In individuals with renal impairment or conditions associated with intestinal malabsorption, for example inflammatory bowel disease, VZIG may be considered as long as their antibody levels suggest they will benefit.
