Antibody test - chickenpox (varicella)

Why undergo serological testing for varicella (chickenpox)?

The presence of IgG antibodies in the blood serum indicates that the individual has either had a previous varicella infection or has been vaccinated against it, thereby developing immunological memory to the virus. This serological test does not differentiate whether the antibodies were produced as a result of natural infection or vaccination.

Determination of VZV-IgG antibodies is particularly recommended in the following cases:

• prior to vaccination against varicella,
• after high-risk exposure to an infected individual,
• in pregnant women or women planning pregnancy with uncertain varicella history,
• in healthcare workers and medical personnel, especially if they have been exposed to the varicella-zoster virus (VZV) or are candidates for vaccination,
• in immunocompromised individuals, where it is important to assess their level of protection against the virus.

The test is not suitable for diagnosing an ongoing acute infection.

What should you know about chickenpox before having a serological test?

Chickenpox is a highly contagious infectious disease affecting mainly children. It usually has a mild course, but this is exacerbated in people with weakened immunity due to other diseases or special immunosuppressive treatments (10) (13). The disease has a biphasic course:

1. In the first phase, it is manifested by fatigue, malaise and mildly elevated temperature (11) (13).
2. In the second phase, skin changes appear. These begin as small reddenings that escalate to blisters that are first hard and later watery. The blisters burst and heal by scarring (11) (13). At this stage, the patient may also experience redness of the eyes, photophobia, and ear or tooth pain (1).

The most common complications of chickenpox are associated with bacterial infections of the skin and soft tissues in children and pneumonia in adults (12).

The source of infection, varicella-zoster virus, is an infected person in the last stage of the incubation period, which ranges from thirteen to seventeen days (13). It is transmitted by droplet infection, indirectly by objects contaminated with nasal secretions or blister contents. Active deposits of shingles (herpes zoster) are also highly infectious, either by direct contact with blister fluid or by inhalation of viral particles from ruptured blisters (10) (13).

After chickenpox is overcome, long-term immunity develops, but the virus persists in the ganglia of the sensory nerves in a so-called latent form. With immunosuppression, VZV can reactivate and spread to innervated areas, manifesting as local involvement in the form of shingles (13). Chickenpox reinfection is sporadic and may occur in immunocompromised persons (i.e., persons who have a compromised or weakened immune system). Rarely, a second episode of disease may occur in patients who have had chickenpox in neonatal or childhood and have not developed sufficient immunity to infection (14).

Commercially available tests for VZV antibodies can be used to check for immunity to chickenpox, but are not sensitive enough to detect immunity acquired by vaccination - they may give false-negative results.

What´s measured

About vaccination against varicella-zoster virus professional

The World Health Organization (WHO) recommends universal vaccination as one of the main preventive measures in cases where chickenpox affects the health system and poses a public health burden. Despite this, only thirty-nine countries have universal varicella vaccination programmes (14). The 2018 Canadian Immunization Manual describes the positive impact of universal varicella vaccination as follows:

• The rate of improvement in vaccinated persons after just one dose of varicella vaccine is estimated to be 7.2% over 10 years of follow-up (15).
• A basic two-dose regimen for children aged 1 to 12 years showed a 3.3-fold reduction in cumulative risk of disease compared with children who received only one dose (15).

Interpretation of results

In case of purchasing the interpretation of the results, this interpretation is created by an internist from uLékaře.cz.