The varicella vaccine is almost 90% effective against chickenpox but its impact on herpes zoster (shingles) is unknown and needs wider surveillance, according to the researchers.
The varicella virus causes both chickenpox and herpes zoster, which occurs when a latent virus in the brain becomes reactivated and causes a painful rash on the skin, leading to severe pain and burning along nerves.
Since 1995, when the varicella vaccine was first introduced in the US, it has greatly reduced the number of chickenpox cases and deaths from varicella. The vaccine may also have a key role in preventing zoster.
“Even though it has been shown that varicella vaccine has had a major impact on the epidemiology of chickenpox in the US, we do not know what impact, if any, the widespread use of varicella vaccine will have on the epidemiology of herpes zoster or shingles – its incidence, age distribution and severity,” said Dr Marietta Vazquez, assistant professor in the department of pediatrics at Yale School of Medicine.
The researchers noted that a study shows a significant decline of 66% in mortality due to varicella since the universal child vaccine program was launched in 1995.