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Value of Vaccines 2020

Chickenpox: a ubiquitous, but now preventable, infection

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Professor Karina Butler

Chair of the National Immunisation Advisory Committee, RCPI
Consultant Paediatrician & Infectious Diseases Specialist, Children’s Health Ireland & UCD Clinical Professor of Paediatrics

The Varicella-Zoster virus affects almost all of us in our lifetime but there are now vaccines that could prevent this.

Varicella-Zoster virus (VZV) causes chickenpox (Varicella) and shingles (Zoster). Primary infection results in chickenpox. The virus then becomes dormant and can later reactivate to cause shingles. In unvaccinated populations, in temperate climates, almost 90% of people have had chickenpox by adulthood. Almost 80% of cases occur in children, mostly those one to five years old. Disease severity is greater in adults than children. Chickenpox is highly contagious and is transmitted by aerosol, droplet, and direct contact. Shingles is not as contagious as chickenpox, however a susceptible person who has direct contact with shingles can become infected and will develop chickenpox.

The chickenpox rash appears 10-21 days after exposure. The pox evolves from flat pink spots that blister with clear, then cloudy, fluid and ultimately dry and crust. Symptoms include temperature up to 38.5oC, occasionally higher, loss of appetite, headache, and malaise for two to three days.

Complications as a result of chickenpox

Complications, infectious and neurologic, although uncommon, can be serious with highest risk for infants, adults, pregnant women, smokers, and the immunocompromised.  Bacterial infections can affect skin, bones, joints etc. Streptococcal necrotising fasciitis, a life-threatening gangrenous skin infection, is a rare complication. Any child with chickenpox with high temperature lasting more than two to three days, with new fever after initial improvement, with significant pain, or refusing to bear weight needs urgent evaluation.

Antiviral treatment

Antiviral treatment is generally unnecessary for uncomplicated chickenpox in children. It can be considered for adolescents and adults because of risk for varicella pneumonia.

The use of the varicella vaccine

Varicella vaccine, a live attenuated vaccine (i.e weakened virus), was first licenced in 1984. The US introduced it for routine childhood immunisation in 1995. It is routinely recommended in many countries. Varicella vaccines are proved to be highly immunogenic, efficacious and safe. Vaccination can protect approximately 86-98% of children and 75% of adolescents and adults.

Since introduction, in the US, varicella cases, hospitalisations, and deaths have decreased by more than 90%. Other countries also experienced significant decreases in chickenpox cases following vaccine introduction. Initial concern that vaccine use might result in more shingles has not been borne out. Recent evidence suggests that those vaccinated are less likely to develop shingles than those following natural infection. Some who are vaccinated may still get very mild chickenpox with fewer or no blisters (they may have just red spots) and little or no fever.

Who should not get the varicella vaccine? 

Varicella vaccine, as a live vaccine, should not be given to pregnant women. Pregnancy should be avoided for one month after getting it. Immunocompromsed patients and those on medication affecting the immune system or with family members with immunodeficiencies should check with their doctor about whether they should receive it.

The current status of the varicella vaccine in Ireland

The varicella vaccine is licensed and marketed for use in Ireland. It is recommended for susceptible individuals in specific risk groups ( It is not yet part of the National primary immunisation programme for all children.

Parents can request it from their GP, however the cost for the vaccine and its administration is borne by the parent. The feasibility of adding the chickenpox vaccine to the national programme is currently undergoing evaluation.

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