Source: Thailand Medical News Jan 23, 2020 4 years, 3 months, 2 days, 1 hour, 43 minutes ago
Individuals who are exposed to as a child, with
chickenpox (
varicella) are around 30% less likely to develop
shingles (
herpes zoster) over 20 years, finds a study in
The BMJ.
The study results support the theory that re-exposure to the
herpes zoster virus in adulthood (after
chickenpox infection as a child), boosts immunity to
shingles, but does not provide complete protection. In light of these findings, the researchers call for a review of the UK's childhood
varicella vaccination policy, which assumes complete immunity for between 2 and 20 years.
Typically, primary infection with
varicella zoster virus causes
chickenpox in children. After this initial infection, the virus remains in the body as a dormant infection, and reactivation, often decades later, causes
shingles.
The previous theory that re-exposure to the
varicella zoster virus in adulthood boosts immunity to
shingles (known as "exogenous boosting") has gained widespread support. As such, the UK and many other countries don't offer routine childhood
varicella vaccination as this would remove circulating virus in the community.
However more recent data suggest that boosting may not be long lasting.
As such a team of UK researchers set out to estimate the risk of
herpes zoster after exposure to a household member with
varicella.
Their study findings are based on UK general practice and hospital records for 9,604 adults (18 years and over; 69% women) diagnosed with
herpes zoster between 1997 and 2018 who lived with a child (18 or under) with
varicella during an average 15-year observation period.
It was observed that average age at
zoster diagnosis was 41 years and at first known exposure to
varicella was 38 years.
After making adjustments for age, calendar time, and season, strong evidence suggested that in the two years after household exposure to a child with varicella, adults were 33% less likely to develop
zoster compared with baseline (unexposed) time.
It was also observed that in the 10 to 20 years after exposure, this protective effect waned slightly but adults were still 27% less likely to develop
zoster compared with baseline time. A stronger boosting effect was seen among men than among women after exposure to
varicella.
However, this is an observational study, so can't establish cause, and the researchers point out that
varicella may be under-recorded as it does not always require a visit to the doctor. Nevertheless they used a large, nationally representative sample and were able to adjust for potentially influential factors.<
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The authors told
Thailand Medical News, "These findings cannot be used to justify for or against specific vaccination schedules. They do, however, suggest that previous mathematical models, estimating the effect of exogenous boosting in childhood
varicella vaccination policy in the UK, that assume complete immunity for between two and 20 years may need revisiting."
Reference : Risk of herpes zoster after exposure to a varicella case: self-controlled case series study using UK electronic healthcare data exploring the exogenous boosting hypothesis, BMJ (2020). DOI: 10.1136/bmj.l6987
