Levin 2018.

Methods	Study design: phase 3, randomised, placebo‐controlled, blinded (participant, investigator, sponsor) Duration: 28 days following any vaccination and 4 months for serious AEs throughout the study (September 2015 to January 2016)
Participants	Inclusion criteria Setting: outpatient Country: USA, 38 centres Number: 882 participants; treatment (N = 440), control (N = 442) Participants' health status: healthy participants with a history of varicella or residence in a VZV‐endemic country for 30 years Age: mean ˜ 61 years Sex: ˜ 59.9% female Other relevant information: aged ≥ 50 years ˜ 85.2% Caucasian (understood to be white) Exclusion criteria "Subjects were excluded if they had a history of: hypersensitivity to vaccine components; herpes zoster or prior receipt of any varicella or zoster vaccine; receipt of an influenza vaccine for the 2015–2016 influenza season; or other conditions that could influence the immunogenicity and safety assessments of either vaccines"
Interventions	Treatment group Participants received LZV (blinded) in the right arm and IIV4 (open‐label) in the left arm on day 1 and placebo (blinded) in the right arm at week 4 (concomitant group) (N = 440) Control group Participants received placebo (blinded) in the right arm and IIV4 (open‐label) in the left arm on day 1 and LZV (blinded) in the right arm at week 4 (sequential group) (N = 442)
Outcomes	Immunogenicity and safety Serious adverse events throughout the study Systemic and elevated temperatures (100.4 °F (38.0 °C) oral or equivalent) within 28 days after any study vaccination Injection site adverse events within 28 days after any study vaccination
Purpose of the study	Evaluate the immunogenicity, safety, and tolerability of 1 dose of LZV administered concomitantly with IIV4
Funding sources	Merck Sharp & Dohme Corp
Conflicts of interest	Employees of Merck Sharp & Dohme Corp (UKB, JG, JM, JES, EB, ZP). Employees may hold stock or stock options, or both, in the company. All authors have been investigators for the sponsor.
Notes	IIV4 (open‐label) was administered in the left arm for all participants on day 1. IIV4 ‐ inactivated quadrivalent influenza vaccines. "IIV4 for the 2015–2016 influenza season was obtained from a commercial source and provided to the study sites as open‐label inventory (Fluzone Quadrivalent vaccine; Sanofi Pasteur, Swiftwater, PA, USA" All injection site adverse events were considered vaccine‐related. We used ITT analysis.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Central randomization procedure"
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding (performance bias and detection bias) All outcomes	Low risk	"Blinded (subject, investigator, sponsor)"
Blinding of participants and personnel (performance bias) All outcomes	Low risk	"The lyophilized ZV and placebo were supplied in 0.65‐mL single‐dose vials and stored at 2‐to‐8 C. The ZV and matching placebo were reconstituted with sterile diluent immediately prior to administration, and were indistinguishable from each other"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	"Blinded (subject, investigator, sponsor)"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Clear patient flow
Selective reporting (reporting bias)	High risk	The results for adverse events proposed in the methodology were not all presented.
Other bias	Unclear risk	Insufficient information