Management of Infants and Pregnant Women Exposed to Chickenpox (Varicella)/Shingles (Zoster)

Introduction

Varicella zoster virus (VZV) causes chicken pox (varicella) and shingles (herpes zoster).  In pregnant women and neonates, VZV can result in severe and even life-threatening varicella disease. Individuals in these groups, who are exposed to chickenpox/ shingles, should be assessed and, for those identified as susceptible, post-exposure prophylaxis (PEP) is recommended to attenuate disease and reduce the risk of complications such as pneumonitis, rather than to prevent infection.

Previously, varicella zoster immunoglobulin was administered in those at risk, but due to a severe national shortage as a result of a manufacturing issue from the sole UK supplier in July 2018, an expert working group was convened. Restrictions on the use of varicella zoster immunoglobulin (VZIG) were implemented whilst supplies of VZIG were limited and stock prioritised. Antivirals were advised as suitable alternatives in immunocompromised contacts and pregnant women exposed from 20 weeks' gestation.

In November 2023, the Joint Committee on Vaccination and Immunisation (JCVI) recommended a universal varicella programme as part of the childhood immunisation schedule, administered as MMRV (measles, mumps, rubella, varicella) at 12-18 months as a two-dose schedule.

Summary of update from the revised PHE guideline April 2022

In summary, antivirals are now recommended for post-exposure prophylaxis for all at risk groups apart from susceptible neonates exposed within one week of delivery (either in utero or post-delivery). VZIG is recommended for those for whom oral antivirals are contraindicated. 

Scope

This guideline is applicable to pregnant women and their neonates who have been exposed to chicken pox, or shingles. It also provides recommendations for infants hospitalised since birth who are premature or who other underlying conditions which put them at increased risk of infection.  

Immunosuppressed individuals are not included, for further information see Public Health England April 2022 guidance.

Purpose

1. Timely treatment and investigations in those exposed to chicken pox (varicella) or shingles (herpes zoster) 

2. Identify which individuals should receive VZIG.

3. Identify which individual should receive PEP.

Definitions

Varicella is also known as chicken pox. 

Herpes zoster (HZ) is also known as shingles.

Neonates are defined as infants up to 28 days old.

Post exposure prophylaxis is recommended for individuals who fulfil all the following 3 criteria

• Significant exposure to chickenpox (varicella) or shingles (zoster) during the infectious period

• At increased risk of severe chickenpox such as immunosuppressed individuals*, neonates, and pregnant women 

• No antibodies to varicella-zoster virus (VZV) – urgent VZV antibody testing can be performed within 24-72 hours, depending on whether the laboratory operate during weekends and bank holidays.

*For the purposes of this guideline, it will only include pregnant women and neonates, for further information re: Immunocompromised individuals, see Guidelines on post exposure prophylaxis for varicella or shingles (publishing.service.gov.uk) Jan 2023

Infectious Period

• Chicken pox: 24 hours prior to rash onset to 5 days after rash (immunocompetent individual) or until all lesions have crusted over (immunosuppressed individuals). 

• Shingles: onset of rash until all of the lesions have crusted over.

Three aspects of exposure to VZV during the infectious period are relevant when considering the need for PEP for a susceptible high-risk individual, these include:

• The type of VZV infection

• The timing of exposure

• Closeness and duration of contac

A. Type of VZV infection in index case: 

PEP should be issued only for those in contact with an individual with:

• Chickenpox 

• Disseminated shingles 

• Exposed shingles lesions (for example ophthalmic shingles or family member in whom it is not possible to cover the lesions at all times) 

• Localised shingles on any part of the body, if the index case is in an immunosuppressed individual in whom viral shedding may be greater 

B. Timing of the exposure 

• Continuous exposure to a case of chickenpox/ shingles (see definitions in section 1.7 A ‘Type of VZV infection in index case’ above), for example household member, nursery, or care worker 

• More than one exposure to a case of chickenpox/shingles (for example family friend who visited on more than one occasion during the infectious period) 

• Single exposure to a case of chickenpox during the infectious period from 24 hours before onset of rash until 5 days after rash appearance in immunocompetent individuals

• Single exposure to a case of shingles (see definitions in section 1.7 A ‘Type of VZV infection in index case’ above)  during the infectious period from onset of rash until the lesions have crusted over (in immunocompetent individuals, this is usually 5 days after rash appearance) 

 C. Closeness and duration of contact 

• Pregnant women, neonates in the first week of life and vulnerable infants up to the age of one year require PEP if exposed to the following contacts with varicella or herpes zoster 

  • Household contacts

  • Contacts in the same small room (for example in a house or classroom or a 2 to 4 bed hospital bay) for a significant period of time (15 minutes or more) 

  • Face to face contacts, for example while having a conversation 

Guidance for specific at-risk groups

Assessment of susceptibility in pregnant women and neonates (see Table 1):

Immunocompetent individuals and pregnant women
Varicella -zoster virus infection during the first 20 weeks of pregnancy can lead to fetal varicella syndrome, which includes microcephaly, cataracts, growth retardation limb hypoplasia, and skin scarring. Varicella-zoster virus can cause severe maternal disease and this risk is greatest in the second or early in the third trimester. The rationale for PEP in pregnant women is two-fold: reduction in severity of maternal disease and theoretical reduction in the risk of fetal infection for women contracting varicella in the first 20 weeks of pregnancy. In late pregnancy, PEP may also reduce the risk of neonatal infection. However, given the risks of severe neonatal varicella in the first week of life, VZIG is also given to infants born within 7 days of onset of maternal varicella. 

• If there is a previous history of chickenpox, shingles or 2 doses of varicella vaccine in immunocompetent individuals, including pregnant women, no testing or PEP is required, as they are deemed to have sufficient evidence of immunity.

• If there is no/unknown previous history of chickenpox/shingles or 2 doses of varicella vaccine in pregnant women, urgent antibody testing looking for varicella IgG should be performed on a recent blood sample. 

• Pregnant women with antibody levels VZV IgG <100mIU/mL, who are exposed to chickenpox or shingles at any stage of pregnancy, should be offered PEP (antivirals, or VZIG if antivirals contraindicated). Antiviral agents include aciclovir and valaciclovir. (see Table 2)

  • Oral aciclovir 800mg 4 times a day from day 7-14 of exposure for 7 days. 

  • Oral valaciclovir 1000mg 3 times a day can be used as a suitable alternative. 

• VZIG should only be offered to pregnant women who are unable to take oral antivirals due to hyperemesis, or who have renal impairment or intestinal malabsorption (see Table 3 for VZIG dosing). Note the dosing of aciclovir in renal impairment (glomerular filtration rate <10mL/minute/1.73m²) as per BNF dosing. If, a pregnant woman presents with a varicella-like rash, they should be changed onto a therapeutic dose of Aciclovir 800mg 5 times a day or 1000mg Valaciclovir 3 times a day for 7 days (starting from the day of onset of the rash)

• If severe chickenpox develops, the woman should be admitted to hospital and treated with IV Aciclovir

Table 1: Risk assessment for pregnant women with a confirmed significant exposure to chickenpox or shingles

Table 2. Recommended doses of oral antivirals 

Table 3. Dose of VZIG for prophylaxis

 *IM injection is contraindicated in those with bleeding disorders, IV is a suitable alternative, needs discussion with pharmacy.

2.2 Neonates

The risks of life-threatening complications are particularly important in neonates in the first week of life. The risk assessment needs to take a number of factors into account including the presence of maternal antibodies, prematurity, timing of exposure, and whether the infant is still hospitalised

VZIG is only indicated for the neonate if they are born to VZV seronegative mothers and are exposed postnatally to chicken pox in the first week of life, or if born to a mother who developed varicella in the period 7 days before to 7 days after delivery. If the mother developed varicella 4 days before to 2 days after delivery, IV Aciclovir (10mg/Kg three times per day for 10 days) should be administered, in addition to VZIG. 

If the neonate is born more than 7 days after the onset of maternal chickenpox or the mother develops chickenpox more than 7 days after the neonate is born, then PEP with VZIG is not indicated.

 In addition to the case scenarios stated above related to neonates below the age of 7 days, there are vulnerable infants who are eligible to VZV PEP until they turn 1 year of age.  See table 4 for additional details. 

Table 4. Risk assessment for neonates or infants with a confirmed significant exposure to chickenpox or shingles

Implementation and training

For circulation to paediatric trainees and consultants from local lead. No further training considered necessary.

Process for monitoring compliance

Seek feedback from the neonatal governance leads at Princess Anne and Portsmouth neonatal unit, if happy they can update the neonatal leads in regional district general hospitals. Future audits will investigate the use of VZIG.

References

1.Public Heath England, Guideline on post exposure prophylaxis (PEP) for varicella (chickenpox) or shingles January 2024

2. Published 27 April 2022, last updated 29 September 2023 - https://assets.publishing.service.gov.uk/media/63e230638fa8f50e86ff1ae4/UKHSA-guidelines-on-VZ-post-exposure-prophylaxis-january-2023.pdf

Appendix 1 - Neonatal Varicella Zoster in immunocompetent pregnant women

Appendix 2 - Neonatal Varicella Zoster in immunocompetent Neonates

Appendix 3 - Neonatal Varicella exposure in utero and postnatally

Appendix 4 - Post Exposure prophylaxis for newborn infants exposed to varicella-zoster virus

Appendix 5 - Post Exposure prophylaxis for newborn infants exposed to varicella-zoster virus