What are the side effects of varicella
vaccine ?



Varicella vaccine has a low reactogenicity and most of the children and adults tolerate the vaccine well. Detailed follow-up studies done for 6 weeks after vaccination have revealed very few side-effects and these are transient and of low severity. These have included pain at the site of injection, fever and papulo-vesicular eruptions. In a four weeks follow-up, double-blind placebo controlled study; there was no significant difference in the nature or incidence of symptoms in children (aged 12-30 months ) receiving the vaccine or placebo. The high-risk patients tend to develop papulo-vesicular eruptions that are sometimes accompanied by moderate fever.

A major concern has been whether the risk of zoster in children immunized with the vaccine would be increased. However, in both healthy and leukemic children, the rate of zoster has been similar to or lower than that expected after natural chickenpox. The vaccine strain of the virus is transmissible but primarily from vaccinees with rash. There is no evidence to suggest reversion to virulence of the vaccine strain during transmission. Persons acquiring vaccine virus may have mild rash or subclinical infection resulting in seroconversion. Due to the possibility of transmission of vaccine virus, vaccinees with rash should avoid contact with susceptible pregnant women and immuno-compromised person.

How can one determine if a child is protected against varicella after vaccination ?



Antibody titre against varicella can be determined 6 weeks after immunization. A titre in excess of or equal to 4 is considered protective. However, routine demonstration of the titre is not necessary.

Is it mandatory to do serological testing children and adults prior to vaccination ?



While answering this question, the following facts need to be noted:

1. Varicella has a characteristic rash and is easily diagnosed even by family members.
2. One attack of chickenpox gives life-long immunity against varicella infection.
3. Giving varicella vaccine to an immune individual does not increase the severity or frequency of side-effects, though it may amount to waste of vaccine.
4. Studies carried out in the United States have shown than given a positive history of varicella infection, 93% of children were immune. However, even when there was no history of varicella, as many as 60% were immune. Even when there was no history of previous varicella infection: most adults were still immune to varicella.

Based on these facts, it may be recommended that children who have a definite history of varicella may be considered as immune while those children who have a doubtful history or on history of having suffered from varicella previously, may be considered as non-immune and vaccinated. In case of adults, however, recommendation regarding serological testing will depend upon relative costs of testing and vaccination.

What are the indications for the use of varicella vaccine ?


Varicella vaccine is not a part of routine immunization in children in India. However, American Academy of pediatrics (AAP) and Advisory committee on Immunization practices (ACIP) have provided certain recommendation in this regard. These guidelines are on the background of most infections occurring in childhood in that country, where varicella infections are likely to be milder with lesser frequency and severity of complications. AAP recommends that all infants aged 12-18 months be routinely immunized against varicella, those who have had natural varicella infection may, however, be excluded, ACIP recommends that all susceptible children be vaccinated before 13 years. Vaccination with two doses of varicella vaccine is recommended for those above the age of 13 years, if the susceptible individual :

1. Has close contact with those at high risk for serious complications of varicella - e.g. healthcare workers, hospital support staff and family contact of immunocompromised patients
2. Lives or works in an environment where transmission of VZV is likely e.g. teachers of young children, those working in day-care centers, residents and staff in institutional setting, college students and military personnel.
3. Is a non-pregnant woman of childbearing age group.

What benefit will occur if routine childhood immunization against varicella is implemented?



Routine varicella vaccination will prevent morbidity and mortality associated with varicella. It will also offer protection to high-risk individuals as circulation of wild virus will decrease in view of reduced number of susceptible individuals. Whenever a child suffers from varicella he is likely to miss the school and the care-giver is likely to stay at home to look after the child. Routine immunization will lead to saving, as direct (expenses on medications and hospitalization ) and indirect (loss of school attendance, absence at workplace, loss of wages) costs will be saved.

Can one administer varicella vaccine to a child for rheumatoid arthritis on chronic aspirin therapy ?



There is an association between occurrence of Reye's syndrome in children and aspirin administration to children who have varicella infection. So far, there is no evidence that administration of varicella vaccine to a child who receives aspirin leads to Reye's syndrome. However, as a measure of abundant precaution, it is advised that aspirin should not be given for 6 weeks following varicella vaccination. In a child on chronic aspirin therapy, the risks of precipitation of Reye's syndrome due to infection by wild varicella virus and that following vaccination are weighed. The child should be monitored closely if vaccination is administered.