Neonatal chicken pox

Neonatal chickenpox is an infection with significant mortality.

• note that if maternal chickenpox occurs from 1 week before birth to 4 weeks after then there is a risk of severe infection in the infant
  
  
• 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) (1)
  • VZIG (varicella zoster immunoglobulin) is recommended for those for whom oral antivirals are contraindicated
    
    
• exposed infants who receive VZIG should be observed for signs of infection for 28 days after the onset of maternal disease since VZIG may prolong the incubation period of the virus for up to 28 days (2)
  
  
• zoster immunoglobulin is also recommended for varicella zoster antibody negative infants exposed to chickenpox or herpes zoster in the first 7 days of life
  
  
• post-exposure prophylaxis with VZIG is not indicated for neonates (under 7 days old) whose mothers have been exposed during pregnancy and have been found to be VZV IgG negative unless the mother develops chickenpox. In these circumstances, aciclovir for the mother should be considered (5)
  • VZIG is only indicated for the neonate if they are directly exposed postnatally in the first week of life
  • post-exposure prophylaxis is recommended for:
    • Group 1
      • neonates whose mothers develop chickenpox (but not shingles) in the period 7 days before to 7 days after delivery
      • VZIG can be given without VZV IgG antibody testing of the neonate or mother; in addition, prophylactic intravenous aciclovir (10 mg/kg every 8 hours for 10 days) should also be considered in addition to the VZIG for infants whose mothers develop chickenpox 4 days before to 2 days after delivery as they are at the highest risk of fatal outcome despite VZIG prophylaxis
      • as this will be an intrauterine exposure treatment should be started as soon as possible and there is no need to wait for 7 days
    • Group 2
      • VZV antibody-negative infants under one year who have remained in hospital since birth who are born before 28 weeks gestation or weighed less than 1,000g at birth, or,
      • VZV antibody-negative infants who have a severe congenital or other underlying condition that requires prolonged intensive or special care during the first year of life
    • Group 3
      • VZV susceptible neonates exposed to chickenpox or shingles (other than in the mother) in the first 7 days of life
        
        
  • in infants over the age of 4 weeks (regardless of gestation at birth) oral aciclovir is the recommended PEP, unless contraindicated (renal toxicity or malabsorption). If contraindicated, VZIG should be given
    
• about 50% of neonates will become infected if exposed to maternal varicella despite zoster immune globulin prophylaxis (3)
  
  
• in up to 2/3 of infants infected with varicella, the infection is asymptomatic or mild. However, rarely fatal cases have been reported despite administration with zoster immunoglobulin in those with the onset of maternal chickenpox up to 4 days before delivery to 2 days after. It is recommended that early treatment with intravenous acyclovir should be used for infants in this exposure category who develop chickenpox - whether or not they have had varicella immune globulin prophylaxis (4)

Notes (4):

• a Drug and Therapeutics review quoted criteria for administration of varicella immune globulin. This regime has been used in prospective observational studies that have shown varicella globulin vaccination may attenuate infection:
  • their mother's rash develops between 7 days before and 7 days after birth;
  • they were born within the last 7 days, their mother is seronegative and they have had significant non-maternal post-natal exposure (e.g. from a sibling);
  • they have been exposed to chickenpox and are at risk because of potentially inadequate transfer of maternal antibodies. This includes babies born before 28 weeks gestation; or weighing less than 1,000g; or who have had repeated blood sampling with replacement by packed red cell infusion; or those requiring intensive or prolonged special care nursing

Reference:

• UK Health Security Agency. Guidelines on post exposure prophylaxis (PEP) for varicella and shingles (April 2022)
• The Royal College of Obstetricians and Gynaecologists 2007. Green-top Guideline No. 13 – Chickenpox in pregnancy
• The Green Book. Immunisation against infectious disease. HMSO. London 1996.
• Drug and Therapeutics Bulletin 2005; 43(9): 69-72
• UK Health Security Agency. Guidelines on post exposure prophylaxis (PEP) for varicella and shingles (January 2023)