[8] Unlike Shingrix, Zostavax is not suitable for people with immunosuppression or diseases that affect the immune system.

[8][9] It can be considered a therapeutic vaccine, given that it is used to treat a latent virus that has remained dormant in cells since chicken pox infection earlier in life.

[9] As of 2021[update] it was not confirmed whether a booster dose was required,[15][10] but the Advisory Committee on Immunization Practices (ACIP) in the United States recommends Shingrix for adults over the age of 50, including those who have already received Zostavax.

[16] The ACIP voted that Shingrix is preferred over Zostavax for the prevention of zoster and related complications because data showed vaccine efficacy of more than 90% against shingles across all age groups.

[20][21][22] The Zostavax vaccine (both single dose and two-dose regime) is likely effective at protecting people from herpes zoster disease for a duration of up to three years.

[23] Zostavax was shown to reduce the incidence of shingles by 51% in a study of 38,000 adults aged 60 and older who received the vaccine.

Temporary side effects from the Shingrix shots are likely and can be severe enough in one out of six people to affect normal daily activities for up to three days.

[10][5] The live vaccine (Zostavax) is very safe; one to a few percent of people develop a mild form of chickenpox, often with about five or six blisters around the injection site, and without fever.

The antigen is a purified truncated form of the glycoprotein, expressed in Chinese hamster ovary cells.

The AS01B adjuvant suspension is composed of 3-O-desacyl-4'-monophosphoryl lipid A (MPL) from Salmonella (Minnesota strain) and a saponin molecule (QS-21) purified from Quillaja saponaria (soap bark tree) extract, combined in a liposomal formulation consisting of dioleoyl phosphatidylcholine (DOPC) and cholesterol in phosphate-buffered saline solution.

[4] This has raised religious and ethical concerns for some potential users, since that cell line was derived from an aborted fetus.

[37] In 2007, the live vaccine was officially recommended in the US for healthy adults aged 60 and over, but is no longer given out in the United States as of 2020[update], given the superiority of Shingrix.

[43][6] Shingrix was approved for medical use in the European Union in March 2018, with an indication for the prevention of herpes zoster (HZ) and post-herpetic neuralgia (PHN) in adults 50 years of age or older.

[7] From 2013, the UK National Health Service (NHS) started offering shingles vaccination to elderly people.

[51][12] The US Centers for Disease Control and Prevention (CDC) recommends that healthy adults 50 years and older get two doses of Shingrix, at least two months apart.