Varicella zoster virus (VZV) can cause two distinct diseases: chicken pox (varicella) and herpes zoster (shingles). The primary infection with VZV causes chicken pox, a widespread rash occurring with fever, mostly in childhood. The virus can then remain dormant in a person's body and has the ability to reactivate later in life causing shingles. Shingles is a painful rash, occurring mostly in older individuals or those who have a weakened immune system. After resolution of the rash, individuals may experience persistent pain in the same area, called post-herpetic neuralgia.

The purpose of the study is to better understand how the immune system responds to the new herpes zoster (shingles) vaccine (Shingrix®). In particular, looking at certain markers in the blood after vaccination with Shingrix®.

The study will be an open label randomized clinical trial in healthy older adults. There will be two groups of participants: those aged 50 to 60 years or those who are 70 years old and above, both groups will receive the vaccine. This will help compare the immune response to the herpes zoster vaccine in different age cohorts of older adults.