A study looking at VZIG or aciclovir for children who have been exposed to chicken pox during cancer treatment (PEPtalk2)

Cancer type:

Children's cancers





This study compared VZIG and aciclovir to prevent chicken pox in children who are exposed to chicken pox during treatment for cancer.

More about this trial

Doctors often use chemotherapy to treat cancer. This can dampen down the immune system and increase the risk of infection. Children having chemotherapy may find it more difficult to cope with infections such as chicken pox compared to healthy children. 
Sometimes children having chemotherapy for cancer have close contact with someone with chickenpox. They can have medicine to try to stop them getting chicken pox if this happens. 
When this trial was done, there were 2 different types of medicine used in the UK to help prevent children with cancer getting chickenpox:
  • VZIG - an injection of an antibody to boost immunity
  • Aciclovir – syrup or tablets that help prevent viral infections
But doctors weren’t sure which treatment is better at preventing chicken pox. 
The main aim of this pilot study was to see if it would be possible to run a large trial to find out which of these two treatments works best.

Summary of results

This pilot study showed that it would be difficult to run a large trial comparing VZIG and aciclovir for children exposed to chicken pox during cancer treatment.

The research team recruited patients in 2014 and 2015, and published the results in 2018.

The research team looked at 482 children who they thought may be able to take part in this trial. But blood test results showed that 337 of them (70%) had already been exposed to chicken pox. And another 47 may have been exposed to it. These children were unable to take part. These numbers were higher than the research team were expecting.

Some families decided they didn’t want to take part. So the research team were able to register 32 of the original 482 children. 

Only 3 of these children were exposed to chickenpox during the trial. This was lower than the research team were expecting.

These 3 children were put in 1 of 2 treatment groups at random. This means that neither the doctors or patients decide which group they are in. In this trial, all 3 children were put in to the aciclovir group. This means that there wasn’t anyone in the VZIG group.

No one who had aciclovir went on to develop chicken pox. But the research team were unable to compare this to how well VZIG worked.

No one taking part had any side effects from the aciclovir. 

The research team concluded that it was unlikely to be possible to run a large trial comparing aciclovir and VZIG in children having chemotherapy for cancer.

They have identified some parts of the trial design that could be changed. But they suggest researchers look at other ways to decide how best to prevent chicken pox in this group of patients.

We have based this summary on information from the research team. The information they sent us has been reviewed by independent specialists (peer reviewed Open a glossary item) and published in a medical journal. The figures we quote above were provided by the trial team who did the research. We have not analysed the data ourselves.

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Professor Paul Heath

Supported by

Cancer Research UK Clinical Trials Unit University of Birmingham
NIHR Clinical Research Network: Cancer
NIHR Research for Patient Benefit (RfPB) Programme
St George's Healthcare NHS Trust
University of Birmingham
Children’s Cancer and Leukaemia Group (CCLG)

Cancer Research UK trial number


Freephone 0808 800 4040

Last review date

CRUK internal database number:

Oracle 11340

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Rhys was only four years old when he was diagnosed with a brain tumour

A picture of Rhys

"He went through six operations and was placed on a clinical trial so he could try new treatments.”

Last reviewed:

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