Chickenpox

It is important to realize that chickenpox can be prevented and that vaccination, in those countries where the vaccine is available, results in both short and long-term health gains.

What is chickenpox?

Chickenpox (or varicella) is a common disease caused by the varicella-zoster virus (sometimes shortened to VZV).

The chickenpox virus spreads very easily from person to person either through the air or by coming into contact with fluid from the spots of chickenpox (or shingles). Virtually everyone in countries in the West will catch chickenpox at some time in their life. In nine out of 10 people, this happens when they are children. Cases tend to appear later in life in less densely populated rural areas in tropical countries. Since second attacks of chickenpox are uncommon, those people at risk of infection are generally those who have not had chickenpox before and who come into contact with someone with the illness. Spread of infection is especially likely to happen in families and among groups of young children in day care centers or schools. Defences against another attack (immunity) develop after a person has had chickenpox, but the virus still stays in the body and may break out years later to cause the painful rash called shingles (or herpes zoster).

What are the symptoms?

There is usually an interval of 2-3 weeks between catching the virus and the start of the chickenpox illness.

In most children, chickenpox is a mild disease that lasts a few days. The first symptoms to appear are fever, headache and abdominal pain that last for a day or two; a skin rash appears very soon afterwards. The rash consists of small itchy spots that rapidly change to blisters. Crops of spots spread anywhere on the body (and often to the mouth and eyes) over a few days, at the end of which there are 200-500 spots. Children with chickenpox are feverish, and are often uncomfortable, drowsy and irritable.

Chickenpox is contagious from a day or two before the rash appears until all the blisters have dried up. This usually takes 4-5 days.

Are there any complications?

In most children, chickenpox is a short-lived, but uncomfortable, disease that gets better without cause for concern. Scratching of the spots can result in them becoming infected and needing treatment with antibiotics. Even though infected spots heal with treatment, they may leave permanent scarring. Occasionally, chickenpox can lead to serious problems and about one in 500 children will need to be hospitalized. The chickenpox virus infects the liver, the lungs or the brain of a small number of children, which can result in permanent brain damage or death.

The disease is often worse if a person gets chickenpox after the age of 13, with many more spots, high fever and a greater number of complications. One in 50 adults with chickenpox will be admitted to the hospital. In teenagers and adults, the most commonly seen serious complication of chickenpox is infection of the lungs, causing cough and shortness of breath. This often needs hospital treatment and can also be life-threatening.

Others who are at particular risk of complications from chickenpox are those who are taking steroid drugs for asthma or other diseases, smokers, pregnant women and those whose immune systems are weakened by cancer or cancer treatments.

Chickenpox in pregnancy can also be dangerous for the baby. Damage to the unborn baby in the first half of pregnancy is a rare complication of chickenpox. A baby can become seriously ill in the first few weeks of life if the mother gets chickenpox just before, or after giving birth.

Is there any treatment?

There are a number of drugs, given as tablets or by injection, that can be used to treat severe or complicated cases of chickenpox, including an antiviral drug called aciclovir. These treatments are not needed for straight forward cases in children, but should be given to those at particular risk (adolescents, adults and those with weak immune systems) as soon as possible after spots appear. Complications usually need hospital care and treatment with aciclovir injections. However, even with the best treatment, chickenpox will be fatal in a small number of people.

Can it be prevented?

A single injection of vaccine produces immunity to chickenpox in children aged between 12 months and 13 years. In older individuals, two doses given 4-8 weeks apart are needed to produce a satisfactory immune response. The chickenpox vaccine may also be given safely at the same time as other vaccines.

The response to the vaccine prevents chickenpox in more than eight out of 10 people. In the small number of vaccinated people who still get chickenpox, the illness is usually very mild. They also have fewer spots, are less likely to have a fever and recover faster. Severe chickenpox after vaccination is very unusual.

The vaccine is designed to provide lifelong protection against the chickenpox virus. Evidence from those who were among the first to be vaccinated shows that immunity lasts at least 10, and probably 20, years.

What are the risks of vaccination?

The chickenpox vaccine, like any other medicine, can sometimes cause problems. Although, to put this into perspective, the risks associated with the vaccine are much less than those of natural chickenpox disease.

If given correctly, the chickenpox vaccine is a very safe, and mostly healthy adults and children have no problems whatsoever. Soreness or swelling at the site of the injection occurs in about one in five children and in up to one in three adolescents or adults. Fever develops in about one in every 10 people and less than one in every 1000 children. This fever may also be accompanied by seizures (jerking of the limbs or staring).

A mild rash may appear within one month of vaccination in one to two children out of 100 and, very rarely, these children can give chickenpox to unvaccinated people that they come into contact with. On very rare occasions, the virus in the vaccine has reactivated to cause shingles (herpes zoster).

Severe problems, such as pneumonia, loss of muscle control and swelling of the brain (encephalitis), have been reported very rarely after chickenpox vaccine and it is difficult for experts to be sure whether these are caused by the vaccine or have happened by chance.

True allergic reactions to the vaccine hardly ever happen. However, if they do, it is within a few minutes or hours of the injection and results in breathing difficulties, an itchy blotchy rash, dizziness or swelling of the tongue and throat. If this should happen, call a doctor and get the person to a doctor immediately.

Some groups of people should not receive the chickenpox vaccine. These are:

• Persons with a history of severe allergic reactions to gelatine or the antibiotic, Neomycin.
• Persons who had a severe reaction to a previous dose of chickenpox vaccine (for those who need a second dose).
• Pregnant women. Women should also try to avoid getting pregnant for one month after being given a shot of the chickenpox vaccine.
• A person with another moderate or severe illness (with or without a fever) at the time the injection is scheduled. Such persons should wait until they recover before being vaccinated.
• Those who have received a recent transfusion of blood or blood products, who should wait several months before being vaccinated, since there is a possibility that the response will be damped down by substances in the transfused plasma.

Persons with a weakened immune system, whether caused by HIV/AIDS, taken drugs (such as steroids) within the past few weeks, a recent organ or bone marrow transplant, cancer or recent treatment for cancer, should be given the chickenpox vaccine only after discussing the potential risks and benefits with their doctor.

Who would benefit from vaccination?

In theory, anyone over 12 months of age who has never had chickenpox could benefit from vaccination. In some countries (notably the USA) routine childhood vaccination against chickenpox is recommended, whereas in other countries it is mainly targeted at high-risk individuals and their contacts, or adults (such as health care workers and teachers) who have never had chickenpox but who are likely to come into contact with children with chickenpox.

It is also possible that the vaccine could be used to prevent herpes zoster (shingles) because it might boost a person's immunity. This strategy is now being tested. The theory behind this suggestion is that shingles occurs only when a person's defences against the chickenpox virus weaken.

Should I agree to have my child vaccinated?

Vaccination provides a number of benefits to the individual, others at risk and, indeed, the whole of society.

The benefit for young children is the prevention of an uncomfortable few days or, for the unlucky few, a severe and life threatening illness. For older persons without any evidence of previous infection with the chickenpox virus, the risks associated with catching chickenpox are much greater and therefore they have much more to gain from a safe and effective vaccine.

The overall effectiveness of a vaccine program is dependent on a high level (80% or more) of vaccination. The disease could become more common if only half of the parents agree to have their child vaccinated. Therefore, the vaccine needs to be given to all children to obtain maximum benefit.

There are also benefits to others in the community who are at risk of chickenpox. Vaccination leads to a fall in the amount of natural chickenpox virus that is circulating in the community and, in theory, a universal vaccination program could eradicate the chickenpox virus.

In the USA, the introduction of a policy of universal vaccination of infants has been followed by a marked fall in the number of cases of chickenpox and the number of children who need hospital care for chickenpox complications. Adult cases have also fallen as a result of the decrease in natural virus circulating in the community. Vaccinating only some children will reduce, but not eliminate, natural virus and increase the chance of creating a population of adults vulnerable to chickenpox, with its greater risk of complications at that age.

Chickenpox vaccination policies vary from country to country and depend upon a number of factors, including the costs of achieving the hoped-for benefit and national views on the severity of chickenpox in comparison with other health problems.

The benefit of a successful program of chickenpox vaccination of children have been shown in the USA. Savings made on medical care and treatment as well as from parents being absent from work in order to look after their children, easily outweigh the cost of giving the vaccine. Targeted vaccination of susceptible health care and/or teachers is also a cost-effective strategy for society to adopt.