Chickenpox vaccination update

Last year the Health Information and Quality Authority (HIQA) published its Health Technology Assessment (HTA) of adding the chickenpox (varicella) vaccine to the routine childhood immunisation programme. This assessment was requested by the Department of Health following a policy recommendation from the National Immunisation Advisory Committee (NIAC).

As an acute infectious disease, chicken pox causes a blister-like rash, itching, tiredness and fever. In some cases complications can be severe. It also puts a significant burden on the economy as parents can need extended time off work to care for infected children.

HIQA’s assessment found that there was “clear and consistent evidence from a strong evidence base” that the chickenpox vaccine was safe and effective in preventing chickenpox and its complications and that adding the chickenpox vaccine to the childhood immunisation programme was likely to be cost effective.¹ 

The Department of Health told WIN that, based on NIAC’s recommendation and the advice of the chief medical officer, “the Minister has approved the introduction of the varicella vaccine into the Primary Childhood Immunisation Programme, subject to funding being made available via the 2025 Estimates process”.

Those wishing to avail of the vaccine ahead of this will have to do so privately. 

Symptoms and spread

Those incubating varicella may have a temperature and feel non-specifically unwell in the one to two days before rash onset. In children, rash is often the first sign of the disease.

The rash starts off as red spots that typically develop into small fluid-filled blisters (vesicles) that then crust over before healing. The rash usually appears on the head and then the trunk, followed by the arms or legs. Successive crops appear over several days.

The clinical course is generally mild in healthy children with malaise, itching and temperature for two to three days. Adults and children with immunocompromising conditions are more likely to have severe disease and more complications.

Varicella-zoster virus is spread through the respiratory tract and direct contact or inhalation of aerosols from vesicular lesions of acute varicella or zoster with skin lesions. It is highly infectious. Virus incubation to development of the typical rash is from 14-16 days (range 10-21 days). The incubation period may be prolonged in immunocompromised individuals or those who have received immunoglobulin with antibodies to varicella zoster.

Individuals with varicella infection are most infectious for one to two days before rash onset through to the first four to five days, or until the lesions have formed crusts. Shingles is less infectious.

Complications

Of the 58,000 cases of chickenpox every year in Ireland, approximately one in 250 cases will be hospitalised with associated complications.¹ Approximately one-third of people who have had chickenpox will develop shingles at some point during their lifetime due to reactivation of the virus.

The risk of complications in varicella varies with age. Complications are infrequent among healthy children but occur much more frequently in those older than 15 years of age and infants younger than one year of age. Most commonly reported complications include:

• Secondary bacterial skin infection

• Pneumonia (viral or secondary bacterial)

• Neurological complications,meningitis, encephalitis (1.8/100,000 cases).

Death-rate varies by age group and immunologic status:

• 1/100,000 among children one to 14 years of age

• 2.7/100,000 among individuals 15 to 19 years of age

• 25.2/100,000 among adults aged 30-49.

Only hospitalised varicella cases are notifiable in Ireland.

Pregnancy

Infection with varicella in the first 20 weeks of pregnancy can cause a variety of abnormalities in the foetus, including:  low birth weight, underdevelopment of limbs, skin scarring, poor development of localised muscles and brain abnormality. The mortality rate ranges from 1-2%.

Maternal varicella infection from five    days before to two days after delivery may result in overwhelming infection in the infant and a fatality rate as high as 30%. 

Diagnosis

Varicella zoster infection can usually be diagnosed based on clinical presentation (typical rash). Laboratory diagnosis is sometimes sought to confirm diagnosis. The virus can be demonstrated in vesicular fluid in chickenpox and shingles lesions. Serology tests are available and can be used to demonstrate immunity.

Prevention

Varicella infection is prevented using a live attenuated vaccine or varicella zoster immunoglobulin (VZIG). Two doses of varicella vaccine are recommended in both children and adults in specific risk groups, including non-immune healthcare workers, laboratory staff at risk of exposure, household contacts of immunocompromised patients, children in residential units for severe disability and non-immune women of child-bearing age. 

Under specialist hospital supervision and protocols, certain categories of immunocompromised patients may be vaccinated. Women of childbearing age without a history of varicella infection should have their immunity checked. Women with negative serology should be vaccinated prior to pregnancy, if no contraindications exist. Pregnancy should be avoided for three months following the last dose of varicella vaccine. 

See the HSE’s immunisation guidelines for more specific information on varicella vaccination at: www.hse.ie

Reference

1. www.hiqa.ie/reports-and-publications/health-technology-assessment/hta-expansion-childhood-immunisation-schedule