Switching from a 2-dose to a 1-dose program of gender-neutral routine vaccination against human papillomavirus in Canada - a mathematical modelling analysis

Sep 21, 2026

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Worldwide, countries consider whether to replace 2-dose human papillomavirus (HPV) vaccination with a single dose. To guide policy, this analysis projected the population-level impact and efficiency of switching from 2-dose to 1-dose gender-neutral routine HPV vaccination in Canada. Using the HPV-ADVISE transmission-dynamic model, scenarios varied by vaccine efficacy (98% or 90%) and duration (lifelong, 30 years, or 25 years), comparing outcomes for HPV-16 reductions and cervical cancers.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages8

Reading Time20 min

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Background

Methods

Study design

Model description

Results

Interpretation

Objective and policy context

Research Switching from a 2-dose to a 1-dose program of gender-neutral routine vaccination against human papillomavirus in Canada: a mathematical modelling analysis Mélanie Drolet PhD, Jean-François Laprise PhD, Éléonore Chamberland MSc, Chantal Sauvageau MD MSc, Sarah Wilson MD MSc, Gillian H. Lim MSc, Gina Ogilvie MD DrPH, Ashleigh Tuite PhD MPH, Marc Brisson PhD n Cite as: CMAJ 2024 October 7;196:E1136-43. doi: 10.1503/cmaj.240787 Abstract Background: Worldwide, countries are examining whether to implement 1-dose human papillomavirus (HPV) vaccination instead of using 2 doses. To inform policy, we sought to project the populationlevel impact and efficiency of switching from 2-dose to 1-dose gender-neutral routine HPV vaccination in Canada. Methods: We used HPV-ADVISE, an individual-based transmission-dynamic model of HPV infections and diseases, to mathematically model vaccination programs in 2 provinces, Quebec, a province with high HPV vaccination coverage (around 85%), and Ontario, which has lower coverage (around 65%). We examined non-inferior and pessimistic scenarios of the efficacy (vaccine efficacy of 98% or 90%) and average vaccine duration (lifelong, 30 yr, or 25 yr) of 1 dose compared with 2 doses (98% vaccine efficacy, lifelong vaccine duration) . Our main outcomes were the relative reduction in HPV-16 (by sex) and cervical cancers, and the number of doses needed to prevent 1 cervical cancer. Results: Our model projected that 1-dose HPV vaccination would avert a similar number of cervical cancers as 2 doses in Canada, under various scenarios. Under the most pessimistic scenario (25-yr vaccine duration), 1-dose vaccination would avert fewer cervical cancers than 2 doses, by about 3 percentage points over 100 years. All 1-dose scenarios were projected to lead to elimination of cervical cancer (< 4 cervical cancers/100 000 femaleyears) and to be a substantially more efficient use of vaccine doses than a 2-dose scenario (1-dose v. no vaccination = 800– 1000 doses needed to prevent 1 cervical cancer; incremental doses for 2-dose v. 1-dose vaccination > 10 000 doses needed to prevent 1 additional cervical cancer) . Interpretation: If the average duration of 1-dose protection is longer than 25 years, a 1-dose HPV vaccination program would protect those vaccinated during their peak ages of sexual activity and prevent a similar number of HPV-related cancers as a 2-dose program, while being amore efficient use of vaccine doses. In April 2022, the World Health Organization (WHO) Strategic Advisory Group of Experts on Immunization (SAGE) announced that human papillomavirus (HPV) vaccination with a single dose could be considered for people aged 9–20 years.1 This advice was based on evidence from clinical trials indicating very high and sustained protection against HPV infections with a single dose.2–4 Since then, updated data from the Costa Rica HPV Vaccine Trial (CVT) showed stable antibodies up to 16 years after 1-dose vaccination5 and the Kenya single-dose HPV vaccine efficacy randomized controlled trial (KEN SHE RCT) showed 98% 1-dose efficacy after 36 months.6 The SAGE announcement was also based on modelling findings that suggested that 1-dose vaccination could lead to similar population-level reductions in cervical cancers as 2 doses in low-and middle-income countries, while being a more efficient use of vaccine doses, assuming that 1-dose protection lasts longer than 20 years.7,8 Most of the 35 countries or so that have adopted 1-dose HPV vaccination are low- and middle-income countries. As of May 2024, about half a dozen high-income countries have adopted a 1-dose vaccination strategy (e.g., United Kingdom, Australia), while some have decided to remain with 2 doses (e.g., Sweden) and many others are evaluating the issue.9,10 Several high-income countries, such as Canada, have been vaccinating against HPV for more than 15 years and are now observing substantial reductions E1136 CMAJ | Oct

FAQs

What was the main goal of the study in Canada?

To project the population-level impact and efficiency of switching from a 2-dose to a 1-dose gender-neutral routine HPV vaccination program in Canada to support policy recommendations.

How did the study model vaccination programs and disease outcomes?

It used HPV-ADVISE, an individual-based transmission-dynamic model of HPV infections and progression to HPV-related cancers, evaluating outcomes for females and males.

What did the model predict under different 1-dose vaccine duration scenarios?

If average 1-dose protection lasted longer than 25 years, 1-dose vaccination would avert a similar number of cervical cancers compared with 2 doses; under the most pessimistic 25-year duration, it would avert fewer cancers by about 3 percentage points over 100 years.

Sep 21, 2026

Upload by Rowan