Palatability testing of a new paediatric formulation of valacyclovir in children 4-12 years of age and at least one of their parents. Children will be included, who received (val)acyclovir prophylaxis in the past, or will probably need it in the future i.e. children with primary immune deficiency or cancer.

Inclusion Criteria:

• Subject is at least 4 years of age.
• Subject weighs at least 15kg.
• Subject is capable of performing the taste assessment, according to the investigator's judgement.
• The child and parent(s) are willing to participate in the taste assessment.
• Signed informed consent by the legal guardian for participation of the child and if the parent also wants to participate: signed informed consent for their own participation, prior to start of the study.

Exclusion Criteria:

• Documented history of sensitivity/idiosyncrasy to medicinal products or excipients.
• Presence of any condition that influences taste sensation (such as upper respiratory infection, febrile illness within 3 days before the first dose, mucositis or use of medication that influences taste perception, as described in the label information).