What is Chickenpox? Varicella, commonly known as chickenpox, is a highly infectious disease caused by human herpes virus type 3 (varicella-zoster virus). The illness begins with fever and/or general unwellness for a day or two followed by a rash, which starts out as small pimples, which change to blisters with a red base. The rash usually starts on the head and then trunk and then moves to the limbs. f How do you catch it? Chickenpox is spread by droplet infection (coughing and sneezing) and also by direct contact with weeping blisters. How Infectious is it? It is highly infectious, from up to 2 days before appearance of the rash until blisters have crusted (usually about 5-7 days). If one person has chickenpox, about 85%
of their close contacts will get it too, unless they have already had the disease (or the relevant vaccine). Is it serious? Chickenpox is usually, but not always, a mild, self-limited disease in otherwise healthy children. However the severity of disease and risk of complications can
be greater in adults. Complications can include severe tissue infection, low platelet count, pneumonia and inflammation of the joints, kidneys and liver.
In New Zealand it is estimated in most years there are approximately 50,000 chickenpox infections, of which 150-200 result in hospitalisation, 1-2 cases result in long-term disability or death, and 0.5-1 cases result in severe congenital varicella syndrome. About two-thirds of the complications occur in otherwise healthy children, and less than one-tenth in children with a disease associated with immune-suppression. What are the risks? Chickenpox can cause severe and even fatal disease in immune suppressed individuals (eg, children with acute leukaemia, or in those having steroid treatment in tablet or
injection form) and in pregnant women. Mortality in normal healthy children is less than 2 per 100,000 cases, increasing up to 15 fold in adults. The lesions may leave mild
scarring in some skin types. Shingles is a long-term complication that is not immediately apparent but can appear decades after the disease. Who is most at risk? Pregnant non-immune women. If a mother has chickenpox in weeks 8-20 of pregnancy, there is a 1-2% chance of fetal abnormalities, eg scars, eye problems, poor growth,
underdevelopment of an arm or leg, small head size, delayed development or mental retardation. (Some babies have only one of these defects, some have them all.)
There is a high risk of serious disease for the infant if the mother has chickenpox between the 5th day before delivery, and two days afterwards.
How do you treat it? Try to prevent scratching and infection of blisters – give lukewarm baths containing bicarbonate of soda or other anti-pruritic (anti-itching) medication
prescribed by your doctor. Keep the patient cool and give plenty of drinks. How can you prevent it? A vaccine given by injection is available for those aged over 9 months. Most people (95%) who have this vaccine will not get chicken pox, but if someone who has had the
vaccine does get chickenpox, it is usually very mild. The vaccine costs approximately $60-$90 per dose. Also, if given within 3-5 days of exposure, the vaccine may prevent,
or will modify, the severity of chickenpox. Who can have the vaccine? Children aged 9 months to 12 years inclusive (1 dose) People 13 years of age and over. (2 doses at least 6 weeks apart) Adults who are working with children and have never had chickenpox disease should consider vaccination. The chicken pox vaccine is a Prescription Medicine. Discuss any further concerns/issues with your doctor, nurse or local immunisation co-ordinator. Who should not have the vaccine?- People with previous severe allergic reaction to:
- Gelatine
- Neomycin (an antibiotic)
- A previous dose of chickenpox vaccine - Pregnant women should wait until after giving birth before having the vaccine and then they should not get pregnant for 3 months after having the vaccine.
- People who are moderately or severely ill should usually wait until they recover before having chickenpox vaccine
Who should ask specialist advice about the vaccine? People who live with a household member, who is immunocompromised and not immune to chickenpox, should discuss options further with their doctor. Immunosuppressed non-immune individuals can, rarely, get chickenpox transmitted from a vaccinee, and may be quite ill - as they would if they caught chickenpox disease from anyone.
People should check with their doctor if they: - Have a disease that affects the immune system
- Are being treated with drugs that affect the immune system e.g. steroids, for 2 weeks or more
- Have any type of cancer
- Are having cancer treatments with x-rays or drugs
- Have recently had a transfusion or have been given other blood products
What are the possible side effects from the vaccine? - Fever (1:10 or less)
- Mild rash - very rarely infectious (1:20 or less)
- Seizure caused by fever (1:1,000 or less)
- Pneumonia (extremely rare)
- Pain and/or swelling at injection site is not uncommon (1:5 children, 1:3 adults) - This is an indication that the immune system has recognised, and is responding to,
the vaccine
How long does the protection from the vaccine last? Follow-up studies also show that almost all vaccinated individuals remain immune for at least 20 years. How can I find out more? Check with your doctor, nurse or local immunisation co-ordinator, or call IMAC on 0800 IMMUNE (466 863) References:
Chin, J (ed) 2000. Control of Communicable Diseases Manual (17th edition).
Washington: American Public Health Association
Immunisation Handbook 2002 New Zealand. Wellington: Ministry of Health Immunisation Advisory Centre: August 2005 TAPS NA 9268
Vaccines are prescription medicines. Talk to you nurse, doctor or midwife about possible risks and the benefits of immunisation. |
