Viral infections

Children and adolescents with cancer are more at risk of infections because of the disease itself and because of the treatment, both of which can affect the immune system.

There are certain infections that are dangerous for cancer patients, in particular viral infections such as chicken pox and measles.  

This page aligns with CCLG guidelines and UK Health Security Agency (UKHSA) guidance on post-exposure prophylaxis for varicella and shingles, which applies to England. For services in Scotland, Wales and Northern Ireland, follow local protocols adapted from UKHSA recommendations. 

Families must contact their treatment centre immediately if their child or young person (CYP) with cancer has been exposed to or is suspected to have an infection.  Management of post-exposure prophylaxis and / or treatment will be coordinated by the haem/onc team.

Chicken pox (varicella)

For immunosuppressed individuals, chicken pox can result in severe and sometimes life-threatening disease. If parents ask community professionals for advice with regards to chicken pox contact, please advise them to contact their ward.

Risk of infection from chicken pox

  • A significant contact is classed as five minutes of conversation with an infected person or being in the same room for 15 minutes. 
  • Chicken pox can be infectious from 24 hours before, and 4-7 days after, onset of rash and may continue until all lesions have crusted over  
  • Siblings and parents with chickenpox can infect other in-patients so should be advised not to visit the ward. 
  • Hand gel is insufficient to prevent cross infection on inpatient/outpatient wards with immunosuppressed patients. Hand washing with soap and water is advised 

If significant exposure occurs: 

  • Families must contact their Principal Treatment Centre (PTC) immediately
  • The haem/onc team will assess immune status and antibody testing may be arranged
  • Post-exposure prophylaxis (PEP) may be required

As of 2024, oral antivirals (aciclovir or valaciclovir) are now the first choice for PEP rather than VZIG (VZV immunoglobulin). However, VZIG can still be used if oral antivirals are contraindicated (UK Health Security Agency, 2025). 

VZIG was historically recommended as PEP for those at risk, but due to severe national shortage, restrictions on its use have been implemented to prioritise stock for the most vulnerable groups (UK Health Security Agency, 2025). 

 VZV-Vaccine (live: for active immunisation) 

  • Can be given to susceptible, immunocompetent, non-pregnant staff via Occupational Health within 4 days of exposure. 
  • Can be given to non-immune siblings and parents of patients via GP 

Chicken pox infection – treatment

Any child / adolescent with cancer who develops vesicles or rash suggestive of varicella should be urgently assessed by their cancer team and 

  • Swabs taken and sent to virology
  • Usually admitted and typically treated with high dose IV aciclovir for at least 7 days
  • May require IV fluids

Shingles (Herpes Zoster)

Shingles is caused by the same virus as chicken pox, the varicella zoster virus. Shingles can only occur if you have had chicken pox and it is caused by reactivation of the virus. This can happen when immunity is low. The virus travels along a nerve path and will appear as a rash on the skin supplied by that nerve. Shingles is predominantly transmitted by direct contact with vesicle fluid in immunosuppressed individuals but can be transmitted via infected respiratory secretions.

Any suspected shingles in CYP on treatment require urgent PTC review.

  • IV Aciclovir and will require admission to hospital for at least 3 days, usually up to 7 days 
  • Some patients may complete treatment with oral antivirals in clinically stable 

Cold sores

These are caused by the herpes simplex virus and some CYP get recurrent problems. If they are persistent or troublesome they are usually treated with oral Aciclovir. Cold sores rarely cause major problems but can be uncomfortable and can delay bone marrow recovery after intensive drug treatment. 

Measles  

Measles can be a very serious infection in children receiving chemotherapy. Urgent contact with PTC is require if CYP has contact with confirmed measles and has not had measles before or complete MMR vaccination.  PTC will access immunity and may arrange human normal immunoglobulin (HNIG) with 48 hours of exposure. 

There is no risk to CYP of transmission of the virus from other children who have recently received MMR vaccine. 

Due to a Measles Outbreak in 2026, CCLG has added additional guidance for families.

Pneumocystis jirovecii pneumonia (PCP)

CYP receiving certain chemotherapies may be at risk of an unusual type of pneumonia called pneumocystis. Usually, CYP are prescribed prophylactic co-trimoxazole during treatment.  Symptoms of concern include:  

  • Fever 
  • tachypnoea  
  • persistent dry cough 

(CCLG, 2016)

Suspected infection requires urgent referral to PTC.

Vaccinations/immunisations

Whilst on treatment children and adolescents should not have live vaccinations or immunisations.  The only exception to this is the flu vaccine which should be given in the injection form rather than the nasal vaccine. 

Vaccination planning will be managed by PTC in line with CCLG and UKHSA guidance. 

After completion of treatment: 

  • Booster doses are usually required 6-12 month following treatment 
  • Post stem cell transplant patients follow a separate vaccination schedule directed by PTC 

(CCLG, 2025) 

Immunisations of siblings

Full immunisation is recommended for siblings and household members as this helps to protect the CYP 

  • Annual influenza vaccine is strongly encouraged (injectable is preferred)
  • If sibling/household member receives a live vaccine and develops a rash, the PTC must be informed

Meningococcal disease

Meningitis is a term used for inflammation of the protective layers covering the brain and spinal cord. There are many causes. 

  • Non-infectious causes: cancer, head injury
  • Infectious causes: bacteria, viruses, fungi

Due to an outbreak of bacterial meningitis (meningococcal disease), CCLG has issued additional guidance for families.

Further reading

References

CCLG (2016) Guidelines for the prophylaxis of Pneumocystis jirovecii pneumonia (PJP) in children with solid tumours: Recommendations. Leicester: CCLG.

CCLG (2025). Vaccinations for paediatric patients treated with standard-dose chemotherapy and HSCT recipients. Leicester: CCLG.

UK Health Security Agency (2025) Guidelines on post‑exposure prophylaxis (PEP) for varicella or shingles. London: UKHSA.

Page last updated March 2026