A Phase 1/2 interventional study of Candidate 1: PF-07915234: VZV modRNA Powder for Suspension for Injection and Candidate 1: PF-07915234: VZV modRNA Suspension for Injection in Shingles, Herpes Zoster Infection and Human, sponsored by Pfizer. Terminated at 35 sites in United States. Open to participants aged 50 Years to 85 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-05-04.
Sponsored by Pfizer · Phase 1/2, Interventional, and Prevention
The purpose of this clinical study is to learn about the safety, extent of the side effects (reaction to vaccine), and immune response (your immune system's reaction) of the study vaccine called Varicella Zoster Virus modRNA (VZV modRNA). We are seeking for healthy participants 50 through 85 years of age.
This study will be conducted in 2 substudies: Substudy A (Phase 1) and Substudy B (Phase 2).
Substudy A:
This substudy is the Phase 1 portion of the study. In this substudy, participants will receive 1 of 3 VZV modRNA vaccine candidates (different construct, different dose levels and different formulation [frozen or freeze dry powder]) or the approved shingles vaccine intramuscularly.
Participants will be assigned in 1 of 10 groups in the study. Vaccination will be given either as a 2-dose series using one of two dosing schedules (either 2-months apart or 6-months apart), or (in one of the groups), as a single VZV modRNA vaccine at the first vaccination visit and saline at the second vaccination visit.
Participants will take part in this study for 8 to 12 months depending on the group they are assigned to. Some group(s) will continue into persistence-of-immunity (overtime assessment of effect of vaccine) portion of the study. Those participants assigned to these selected groups will be involved in the study for up to 5 years.
Substudy B:
This substudy is the Phase 2 portion of the study. In this part of the study, participants will receive either VZV modRNA vaccine at selected dose level/schedule/formulation or approved shingles vaccine. This selection was determined from data collected in Substudy A.
Participants will be involved in this study for up to 5 years.
299 studies on the registry are indexed under Herpes Zoster; 55 are open to participants now.
This study's enrollment of 484 is above the median of 160 across 247 interventional studies indexed under Herpes Zoster.
Browse Herpes Zoster studies →Pfizer is the lead sponsor of 3,334 studies on the registry; 149 are open to participants now.
Of its 601 completed or terminated interventional studies of FDA-regulated products, 391 (65%) have results posted.
Counted across the registry records on this site, refreshed daily.
Substudy A: Group 1 to Group 10
Inclusion Criteria:
Substudy A: Group 11 to Group 14
Inclusion Criteria:
Substudy A: Group 1 to Group 10
Exclusion Criteria:
SubStudy B:
Inclusion Criteria:
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis C tests
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Bilirubin
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECG (electrocardiogram)
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Candidate 1, Dose Level 1, lyophilized, 0, 2 months schedule
Biological: Candidate 1: PF-07915234: VZV modRNA Powder for Suspension for Injection
Candidate 1, Dose Level 2, lyophilized, 0, 2 months schedule
Biological: Candidate 1: PF-07915234: VZV modRNA Powder for Suspension for Injection
Candidate 1, Dose Level 3, lyophilized, 0, 2 months schedule
Biological: Candidate 1: PF-07915234: VZV modRNA Powder for Suspension for Injection
Candidate 1, Dose Level 2, frozen, 0, 2 months schedule
Biological: Candidate 1: PF-07915234: VZV modRNA Suspension for Injection
Candidate 1, Dose Level 2, Frozen, 0, 6 months schedule
Biological: Candidate 1: PF-07915234: VZV modRNA Suspension for Injection
Candidate 2, frozen, 0, 2 months schedule
Biological: Candidate 2: PF-07921188: VZV modRNA Suspension for Injection
Candidate 3, Frozen, 0, 2 months schedule
Biological: Candidate 3: PF-07921186: VZV modRNA Suspension for Injection
Shingrix, 0, 2 months schedule
Biological: Shingrix
Shingrix, 0, 6 months schedule
Biological: Shingrix
Candidate 1, Dose level 4, lyophilized, 0, 6 months schedule (saline at month 6)
Biological: Candidate 1: PF-07915234: VZV modRNA Powder for Suspension for Injection
Candidate 2, Dose level 3, lyophilized, 0, 2 months schedule
Biological: Candidate 2: PF-07921188: VZV modRNA Powder for Suspension for Injection
Candidate 2, Dose level 4, lyophilized, 0, 2 months schedule
Biological: Candidate 2: PF-07921188: VZV modRNA Powder for Suspension for Injection
Candidate 2, Dose level 4, lyophilized, 0, 2 months schedule (saline at month 2)
Biological: Candidate 2: PF-07921188: VZV modRNA Powder for Suspension for Injection
Shingrix, 0, 2 months schedule
Biological: Shingrix
Intramuscular injection
Intramuscular injection
Intramuscular injection
Intramuscular injection
Intramuscular injection
Intramuscular injection
SSA: Percentage of participants reporting local reactions
Pain at the injection site, redness, and swelling as self-reported in electronic diaries.
Time frame: For 7 days after Vaccination 1 and Vaccination 2
SSA: Percentage of participants reporting systemic events
Fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain, as self-reported in electronic diaries
Time frame: For 7 days after Vaccination 1 and Vaccination 2
SSA: Percentage of participants reporting adverse events
As elicited by investigational site staff
Time frame: From Vaccination 1 to 4 weeks after last vaccination
SSA: Percentage of participants reporting serious adverse events
As elicited by investigational site staff
Time frame: From Vaccination 1 to 6 months after the last study vaccination
SSA: Percentage of participants reporting medically attended adverse event
As elicited by investigational site staff
Time frame: From Vaccination 1 to 6 months after the last study vaccination
SSA: Percentage of participants with abnormal hematology and chemistry laboratory assessments
As measured at the central laboratory
Time frame: 3 days and 1 week after each vaccination
SSA: Percentage of participants with new electrocardiogram (ECG) abnormalities
ECG abnormalities consistent with probable or possible myocarditis or pericarditis, as judged by a cardiologist
Time frame: 3 days and 1 week after each vaccination
SSA: Percentage of participants with abnormal troponin I laboratory values
as measured at the central laboratory
Time frame: 3 days and 1 week after each vaccination
SSB: Percentage of participants reporting local reactions
Pain at the injection site, redness, and swelling as self-reported in electronic diaries.
Time frame: For 7 days after Vaccination 1 and Vaccination 2
SSB: Percentage of participants reporting systemic events
Fever, fatigue, headache, chills, vomiting, diarrhea, muscle pain, and joint pain, as self-reported in electronic diaries
Time frame: For 7 days after Vaccination 1 and Vaccination 2
SSB: Percentage of participants reporting adverse events
As elicited by investigational site staff
Time frame: From Vaccination 1 to 4 weeks after last vaccination
SSB: Percentage of participants reporting serious adverse events
As elicited by investigational site staff
Time frame: From Vaccination 1 to 6 months after the last study vaccination
SSB: Percentage of participants reporting medically attended adverse events
As elicited by investigational site staff
Time frame: From Vaccination 1 to 6 months after the last study vaccination
SSA: Geometric mean concentrations (GMCs) of glycoprotein E antibodies in proportion of evaluable immunogenicity participant
As measured at the central laboratory
Time frame: At baseline (before vaccination 1), at 1- and 4-weeks after each vaccination and 6-months after last vaccination
SSA: Geometric mean fold rise (GMFR) from before vaccination to each subsequent timepoint in evaluable immunogenicity participants
As measured at the central laboratory
Time frame: At baseline (before vaccination 1), at 1- and 4-weeks after each vaccination and 6-months after last vaccination
SSA: Proportion of evaluable immunogenicity participants with vaccine response in glycoprotein E antibodies from baseline to each subsequent timepoint
As measured at the central laboratory
Time frame: At baseline (before vaccination 1), at 1- and 4-weeks after each vaccination and 6-months after last vaccination
SSB: Geometric mean concentrations (GMCs) of glycoprotein E antibodies in proportion of evaluable immunogenicity participant
As measured at the central laboratory
Time frame: At baseline (before vaccination 1), at 4-weeks after each vaccination and 6-months after last vaccination
SSB: Geometric mean fold rise (GMFR) from before vaccination to each subsequent timepoint in evaluable immunogenicity participants
As measured at the central laboratory
Time frame: At baseline (before vaccination 1), at 4-weeks after each vaccination and 6-months after last vaccination
SSB: Proportion of evaluable immunogenicity participants with vaccine response in glycoprotein E antibodies from baseline to each subsequent timepoint
As measured at the central laboratory
Time frame: At baseline (before vaccination 1), at 4-weeks after each vaccination and 6-months after last vaccination
Plan to share: Yes — Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.
Data sharing details ↗ · www.pfizer.com
Ran from Jan 2023 to primary completion in Sep 2025, 31 months.
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This study is terminated, as verified in Apr 2026. You cannot join it, but the record below documents what was studied.
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