Shingles, also known as herpes zoster, is a viral infection stemming from the reactivation of the varicella-zoster virus (VZV), the same virus responsible for chickenpox. After a chickenpox infection, the virus can lie dormant in nerve cells for decades, potentially reactivating later in life to cause a painful rash with blisters. Vaccines have been developed to prevent or reduce its severity.
The First Approach: Zostavax
The first vaccine, Zostavax, received approval from the U.S. Food and Drug Administration (FDA) in May 2006. Initially, it was licensed for individuals 60 years and older. It was a live, attenuated vaccine, containing a weakened, live form of the varicella-zoster virus to stimulate an immune response.
Zostavax was administered as a single dose. Clinical trials indicated it reduced the risk of shingles by approximately 51% in adults over 60, and by about 70% in those aged 50 to 59. Its effectiveness varied with age, showing reduced protection in older individuals (e.g., 38% for those 70 and older).
Protection also waned over time. It was not suitable for individuals with weakened immune systems due to its live virus component. Merck discontinued Zostavax in the United States in November 2020.
The Current Standard: Shingrix
Shingrix was approved by the FDA in October 2017, marking a significant advancement. Initially approved for adults aged 50 and older, Shingrix differs from Zostavax as a recombinant subunit vaccine, meaning it does not contain live virus. Instead, it uses a specific viral protein (glycoprotein E) combined with an adjuvant to boost the immune response.
Shingrix is administered as a two-dose series, with doses given two to six months apart. Its efficacy is notably higher than its predecessor, demonstrating over 90% effectiveness across all adult age groups, including those over 70. Specifically, it showed approximately 97% effectiveness in adults aged 50 to 69 and around 90% effectiveness in those aged 70 and older.
This higher efficacy also extended to preventing postherpetic neuralgia, a common complication of shingles. Due to its superior efficacy and non-live nature, Shingrix became the preferred vaccine. Its use was further expanded in July 2021 to include adults aged 18 and older who are at increased risk of shingles due to immunodeficiency or immunosuppression.