The chickenpox vaccine may increase the incidence of shingles, according to a recent study The Blaze reported.

Researchers from the Universities of Antwerp and Hasselt found that vaccinating one year olds against chickenpox could temporarily double the incidence of shingles in the wider population, but mainly in younger adults.  This occurs because the vaccine reduces the likelihood of adults who've had the illness as a child being re-exposed to the virus. Re-exposure boosts immunity to shingles, caused by the same virus, Varicella-zoster virus.

Shingles occurs most often in individuals with a declined immunological status, such as HIV or cancer patients. Aging is also assumed to increase susceptibility.

The current study predicts that the temporary effect of a rise in shingles cases dominates in 31 to 40 year olds. This is younger than previously predicted and this age group is less at risk of developing the most serious shingles symptoms. Many countries have avoided introducing universal chickenpox vaccination in children because it was previously predicted that the reduction in chickenpox related disease would be outbalanced by the temporarily increase in shingles-related disease.

A new model developed by the scientists also confounds previous findings on the length of time re-exposure chickenpox boosts immunity to shingles. The effect was thought to last for up to 20 years, but results of the current modeling study show it only lasts for two. The new model is the first based on real immunological and virological data from individuals.

"We were surprised to find that re-exposure to chickenpox is beneficial for so few years and also that the most pronounced effect of vaccination on increasing cases of shingles is in younger adults," says lead author Dr. Benson Ogunjimi.

Ogunjimi said the findings, which are detailed in the journal eLife, should reduce fears about implementing childhood chickenpox vaccination.