Vulnerable children - Some medical conditions make children vulnerable to infections that would rarely be serious in most children, these include those being treated for leukaemia or other cancers, on high doses of steroids and with conditions that seriously reduce immunity. These children are particularly vulnerable to chickenpox, if exposed to these, the parent/carer should be informed promptly and further medical advice sought.

Pregnancy - Anyone who has not had chickenpox is potentially vulnerable to the infection. If a pregnant woman develops a rash or is in direct contact with someone with a potentially infectious rash, this should be investigated by a doctor. Chickenpox can affect the pregnancy if a woman has not already had the infection. Report exposure to midwife and GP at any stage of pregnancy. The GP and antenatal carer will arrange a blood test to check for immunity.