A Phase 4 interventional study of Gardasil® HPV vaccine in HPV Infection and Vaccine Preventable Disease, sponsored by London School of Hygiene and Tropical Medicine. Recruiting at 1 site in Tanzania. Open to male participants aged 14 Years to 18 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-08.
Sponsored by London School of Hygiene and Tropical Medicine · Phase 4, Interventional, and Prevention
Add-Vacc is an unblinded cluster-randomised trial (CRT) with two arms: (i) the national HPV vaccination programme (girls aged \~14 years, control arm) and (ii) the national programme plus single-dose male HPV vaccination given to a multi-year cohort of boys (intervention arm). The CRT will be conducted in 26 communities/clusters (13 per arm) in northern Tanzania. Boys aged 14 to 18 years in the intervention arm will receive one dose of the 4-valent HPV vaccine (Gardasil®) that protects against HPV 6, 11, 16, and 18. Population genital HPV prevalence in 18 to 21-year-olds will be compared between intervention clusters (female and male vaccination) and control clusters (female vaccination only) at 3 years after the intervention. Blood sampling for immune responses and adverse event data collection will be performed in a subset of 200 male subjects in selected intervention clusters.
576 studies on the registry are indexed under Papillomavirus Infections; 132 are open to participants now.
This study's planned enrollment of 10,400 is above the median of 235 across 402 interventional studies indexed under Papillomavirus Infections.
Browse Papillomavirus Infections studies →London School of Hygiene and Tropical Medicine is the lead sponsor of 298 studies on the registry; 15 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Boys will be excluded from HPV vaccination if:
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.
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.
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.
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.
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.
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.
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.
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.
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.
Single dose of the 4-valent HPV vaccine (Gardasil®; Merck \& Co.) offered to all eligible boys aged 14 to 18 years in the 13 intervention communities. Girls aged 14 years are offered 2 doses of Gardasil® through the Tanzanian national HPV vaccine programme
Biological: Gardasil® HPV vaccine
Girls aged 14 years are offered 2 doses of Gardasil® through the Tanzanian national HPV vaccine programme
Biological: Gardasil® HPV vaccine
Single dose 4-valent HPV vaccine in males. Gardasil®, manufactured by MSD, consists of a licensed prophylactic virus-like particle (VLP) vaccine that protects against 4 HPV genotypes (HPV 6, 11, 16, 18).
Also known as: 4-valent HPV vaccine
Impact of adding single-dose male HPV vaccination to the national HPV vaccination programme in girls on population 4-valent HPV genotype prevalence in 18 to 21-year-old females and males
Prevalence of 4-valent vaccine HPV genotype DNA (HPV 6, 11, 16 or 18) in males and females aged 18 to 21 years in intervention clusters and control clusters 36 months post-male vaccination
Time frame: Month 36
Immunogenicity and safety of single dose 4-valent HPV vaccination in boys
Proportion seroconverting to, and geometric mean antibody titres (GMTs) for, HPV vaccine genotypes, and safety and tolerability (local and systemic adverse events), measured in a subset of 200 vaccinated boys
Time frame: Month 12, 24 and 36
Impact of female-only vaccination through the national vaccination programme on population HPV prevalence in 18 to 21-year-old males and females
The proportion of females, and of males, aged 18 to 21 years in the control arm with detectable genital 4-valent HPV vaccine genotype DNA at baseline and at M36.
Time frame: Month 36
Uptake of dose 1 and coverage of dose 2 in eligible target groups for the national HPV vaccination programme;
The proportion of females aged 16 years who received 1 dose of HPV vaccine (uptake) and who complete 2 doses (coverage) by arm at baseline and M36
Time frame: Month 36
Acceptability of a gender-neutral approach to HPV vaccination
Self-reported acceptability of and barriers to receiving male vaccination by community members and to delivering male HPV vaccination by health care workers (HCW)
Time frame: Month 24
Cost-effectiveness of adding a multi-year single dose male HPV vaccination strategy to the national female HPV vaccination programme
Incremental cost-effectiveness ratio for single dose male vaccination plus existing female vaccination programme compared to female vaccination only
Time frame: Month 36
Plan to share: Undecided
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