No 41 - 2026

Revised recommendations for post-exposure prophylaxis against chickenpox in pregnant women

SSI is changing the recommendations for post-exposure prophylaxis (PEP) for pregnant women who have been exposed to chickenpox (varicella). In future, oral antiviral treatment with aciclovir or valaciclovir is recommended instead of varicella-zoster immunoglobulin (VZIG) for pregnant women for whom PEP is indicated. The change is being made in collaboration with a working group comprising representatives from the Danish societies for infectious diseases, gynaecology and obstetrics, and paediatrics.

Background

Chickenpox during pregnancy is rare in Denmark, as the vast majority of women of childbearing age are immune following previous infection. However, primary infection with varicella-zoster virus (VZV) during pregnancy can have serious consequences for both the pregnant woman and the child.

Pregnant women with chickenpox have an increased risk of serious complications, particularly varicella pneumonia, but in rarer cases also hepatitis and encephalitis. The risk to the foetus and the newborn child depends, among other things, on the timing of infection. In the event of maternal infection during the first half of pregnancy, there is a small risk of congenital varicella syndrome.

Maternal infection around the time of delivery can result in severe neonatal varicella, as the child may not have received protective antibodies from the mother before birth.

Until now, seronegative pregnant women have been offered VZIG following relevant exposure. International guidelines have increasingly adopted oral antiviral treatment as PEP, and available data suggest that aciclovir has comparable efficacy to VZIG in preventing chickenpox in exposed pregnant women. Antiviral treatment is also more readily available, simpler to administer and considerably cheaper.

Future PEP for pregnant women

In the event of relevant exposure, it must be established whether the pregnant woman has previously had chickenpox. A history of previous chickenpox can, as a general rule, be regarded as sufficient documentation of immunity, particularly in women born in Denmark. If the pregnant woman has not previously had chickenpox, or if there is doubt about immune status, serological testing for VZV IgG antibodies must be performed as soon as possible. The sample should be sent as an urgent sample and can be analysed at local departments of clinical microbiology. See the diagnostic handbook: Human alphavirus 3 (Varicella zoster virus) antibody (R-no. 277).

In non-immune pregnant women for whom PEP is indicated, antiviral treatment can be used regardless of trimester. Treatment is given for 14 days and initiated as soon as possible after clarification of immune status, but no later than 10 days after exposure. PEP treatment of pregnant women is managed by an obstetrician in a hospital setting and not in primary care.

A choice can be made between treatment with aciclovir or valaciclovir:

• Aciclovir: 800 mg 5 times daily for 14 days
• Valaciclovir: 1,000 mg 3 times daily for 14 days.

Aciclovir has the most extensive safety evidence for use during pregnancy and has been used in pregnant women for many years without evidence of an increased risk of congenital malformations.

Valaciclovir is converted into aciclovir in the body and has the practical advantage that it can be dosed three times daily rather than five times daily, which may improve compliance. Both medicines can be used as PEP in pregnant women and are used off-label for this indication.

Newborns and immunosuppressed persons

No changes are currently being made to the recommendations for PEP in newborns. The choice of PEP for immunosuppressed patients must continue to be based on an individual clinical assessment.

Read more here: Varicella post-exposure prophylaxis (chickenpox).

(K. Bray, I.G. Helmuth, M. Wessman, Department of Infectious Disease Epidemiology and Prevention, R. Datcu, Virology and Microbiological Preparedness, N. Weis, representative of the Danish Society for Infectious Diseases, R. B. Helmig, representative of the Danish Society for Obstetrics and Gynaecology, S. Lund, representative of the Danish Paediatric Society) 

European training programme for field epidemiologists (EPIET) or field microbiologists (EUPHEM)

It is once again possible to apply for admission to the special two-year European training programme for “field epidemiologists”, abbreviated as ‘EPIET’ (European Programme for Intervention Epidemiology Training). During the training programme, participants acquire skills in the surveillance and control of infectious diseases, outbreak detection and management, applied research, communication, etc.

The training takes place during a two-year placement in another European country. It involves “on-the-job training”, meaning that participants will receive a salary during the training programme. Applicants are expected to have relevant education, previous experience in public health and an interest in applied epidemiology.

It is also possible to apply for admission to a corresponding two-year European training programme for microbiologists, EUPHEM (European Public Health Microbiology Training). The training also takes place during a two-year placement in another European country. During the training programme, participants acquire skills in independently performing laboratory tasks in connection with the surveillance and control of infectious diseases, outbreak detection and management, applied research, communication, etc. Applicants are expected to have at least three years of work experience in microbiology or a PhD degree and an interest in applied microbiology.

Both training programmes are offered by the European Centre for Disease Prevention and Control (ECDC) and begin with participation in a joint three-week introductory course in mid-September 2027.

Applicants for EPIET and EUPHEM must be citizens of the EU, Iceland, Liechtenstein or Norway and have a good command of English. The application deadline is 26 October 2026, and applicants are encouraged to inform SSI that they are applying, in consideration of the subsequent process, which takes place in close collaboration between ECDC and SSI.

Further information is available on ECDC's website or by contacting Head of Section Steen Ethelberg (set@ssi.dk), Department of Infectious Disease Epidemiology and Prevention (EPIET), or Senior Researcher Rune Stensvold (run@ssi.dk), Department of Bacteria, Parasites and Fungi (EUPHEM).

(Statens Serum Institut)

Autumn holiday

Unless special circumstances arise, EPI-NEWS will not be published in week 42.