Sex-Specific Immunization for Sexually Transmitted Infections Such as Human Papillomavirus: Insights from Mathematical Models

Bogaards, Johannes A.; Kretzschmar, Mirjam; Xiridou, Maria; Meijer, Chris J.L.M.; Berkhof, Johannes; Wallinga, Jacco

doi:10.1371/journal.pmed.1001147

Cited by 58 publications

(73 citation statements)

References 52 publications

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“…Finally, the large herd effects reported with high vaccination coverage are consistent with predictions from dynamic models. 20–24 …”

Section: Discussionmentioning

confidence: 99%

“…17–19 Despite consistency in model predictions of the direct effects of HPV vaccination in vaccinated girls, uncertainty remains about the potential population-level effects of cross-protection and herd protection (eg, the indirect consequences of vaccinating girls on HPV in unvaccinated boys, men, and adult women), and the vaccination coverage necessary to achieve substantial herd effects. 20–24 This information is crucial to help guide vaccine choices and inform decisions about vaccination of boys and men.…”

Section: Introductionmentioning

confidence: 99%

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Population-level impact and herd effects following human papillomavirus vaccination programmes: a systematic review and meta-analysis

Drolet

Bénard

Boily

et al. 2015

The Lancet Infectious Diseases

586

432

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Summary Background Human papillomavirus (HPV) vaccination programmes were first implemented in several countries worldwide in 2007. We did a systematic review and meta-analysis to assess the population-level consequences and herd effects after female HPV vaccination programmes, to verify whether or not the high efficacy reported in randomised controlled clinical trials are materialising in real-world situations. Methods We searched the Medline and Embase databases (between Jan 1, 2007 and Feb 28, 2014) and conference abstracts for time-trend studies that analysed changes, between the pre-vaccination and post-vaccination periods, in the incidence or prevalence of at least one HPV-related endpoint: HPV infection, anogenital warts, and high-grade cervical lesions. We used random-effects models to derive pooled relative risk (RR) estimates. We stratified all analyses by age and sex. We did subgroup analyses by comparing studies according to vaccine type, vaccination coverage, and years since implementation of the vaccination programme. We assessed heterogeneity across studies using I2 and χ2 statistics and we did trends analysis to examine the dose–response association between HPV vaccination coverage and each study effect measure. Findings We identified 20 eligible studies, which were all undertaken in nine high-income countries and represent more than 140 million person-years of follow-up. In countries with female vaccination coverage of at least 50%, HPV type 16 and 18 infections decreased significantly between the pre-vaccination and post-vaccination periods by 68% (RR 0·32, 95% CI 0·19–0·52) and anogenital warts decreased significantly by 61% (0·39, 0·22–0·71) in girls 13–19 years of age. Significant reductions were also recorded in HPV types 31, 33, and 45 in this age group of girls (RR 0·72, 95% CI 0·54–0·96), which suggests cross-protection. Additionally, significant reductions in anogenital warts were also reported in boys younger than 20 years of age (0·66 [95% CI 0·47–0·91]) and in women 20–39 years of age (0·68 [95% CI 0·51–0·89]), which suggests herd effects. In countries with female vaccination coverage lower than 50%, significant reductions in HPV types 16 and 18 infection (RR 0·50, 95% CI 0·34–0·74]) and in anogenital warts (0·86 [95% CI 0·79–0·94]) occurred in girls younger than 20 years of age, with no indication of cross-protection or herd effects. Interpretation Our results are promising for the long-term population-level effects of HPV vaccination programmes. However, continued monitoring is essential to identify any signals of potential waning efficacy or type-replacement. Funding The Canadian Institutes of Health Research.

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“…Finally, the large herd effects reported with high vaccination coverage are consistent with predictions from dynamic models. 20–24 …”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Population-level impact and herd effects following human papillomavirus vaccination programmes: a systematic review and meta-analysis

Drolet

Bénard

Boily

et al. 2015

The Lancet Infectious Diseases

586

432

View full text Add to dashboard Cite

show abstract

“…We speculate that adding more heterogeneity in the model (ie, by including low-risk individuals or allowing for dispersion of high-risk behaviour among STI clinic visitors) would estimate a smaller impact of the interventions on reducing prevalence. 19 We incorporated site-specific natural clearance of the infections rather than individual-level clearance of infection. This means that when a woman is infected at both anatomical locations, she might clear the infection at one location, but not necessarily at the other.…”

Section: Discussionmentioning

confidence: 99%

What explains anorectal chlamydia infection in women? Implications of a mathematical model for test and treatment strategies

et al. 2016

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ObjectivesFemale anorectal Chlamydia trachomatis (chlamydia) infections are common irrespective of recent anal sex. We explored the role of anorectal infections in chlamydia transmission and estimated the impact of interventions aimed at improved detection and treatment of anorectal infections.MethodsWe developed a pair compartmental model of heterosexuals aged 15–29 years attending STI clinics, in which women can be susceptible to or infected with chlamydia urogenitally and/or anorectally and men urogenitally. Transmission probabilities per vaginal and anal sex act, together with an autoinoculation probability, were estimated by fitting to anatomic site-specific prevalence data (14% urogenital; 11% anorectal prevalence). We investigated the 10-year reduction in female chlamydia prevalence of interventions (universal anorectal testing of female STI clinic attendees or doxycycline use for urogenital chlamydia) relative to continued current care (anorectal testing on indication and doxycycline for anorectal and azithromycin for urogenital chlamydia).ResultsThe transmission probability per anal sex act was 5.8% (IQR 3.0–8.3%), per vaginal sex act 2.0% (IQR 1.7–2.2%) and the daily autoinoculation probability was 0.7% (IQR 0.5–1.0%). More anorectal chlamydia infections were caused by autoinoculation than by recent anal sex. Universal anorectal testing reduced population prevalence modestly with 8.7% (IQR 7.6–9.7%), yet the reduction was double that of doxycycline use for urogenital infections (4.3% (IQR 3.5–5.3%)) relative to continued current care.ConclusionsAutoinoculation between anatomic sites in women might play a role in sustaining high chlamydia prevalence. A shift to more anorectal testing of female STI clinic attendees may be considered for its (albeit modest) impact on reducing prevalence.

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“…However, because immunity bridging data were available for both boys and girls, Australia recommended vaccination for both sexes. Computer simulations have demonstrated that more than 80% female vaccination would achieve sufficient coverage and would be more cost-effective than vaccinating both males and females (224,225). Also, it was calculated that with such high vaccine coverage, herd immunity would be enough to reduce HPV circulation (226).…”

Section: Challenges For a Chlamydial Vaccinementioning

confidence: 99%

Genital Chlamydia trachomatis: Understanding the Roles of Innate and Adaptive Immunity in Vaccine Research

Vasilevsky¹,

Greub

Nardelli-Haefliger

et al. 2014

Clin Microbiol Rev

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SUMMARY Chlamydia trachomatis is the leading cause of bacterial sexually transmitted disease worldwide, and despite significant advances in chlamydial research, a prophylactic vaccine has yet to be developed. This Gram-negative obligate intracellular bacterium, which often causes asymptomatic infection, may cause pelvic inflammatory disease (PID), ectopic pregnancies, scarring of the fallopian tubes, miscarriage, and infertility when left untreated. In the genital tract, Chlamydia trachomatis infects primarily epithelial cells and requires Th1 immunity for optimal clearance. This review first focuses on the immune cells important in a chlamydial infection. Second, we summarize the research and challenges associated with developing a chlamydial vaccine that elicits a protective Th1-mediated immune response without inducing adverse immunopathologies.

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Sex-Specific Immunization for Sexually Transmitted Infections Such as Human Papillomavirus: Insights from Mathematical Models

Abstract: Johannes Bogaards and colleagues use mathematical models to investigate whether vaccinating females only, males only, or both sexes is the best way to achieve the most effective reduction in the population prevalence of sexually-transmitted infections

Cited by 58 publications

References 52 publications

Population-level impact and herd effects following human papillomavirus vaccination programmes: a systematic review and meta-analysis

Population-level impact and herd effects following human papillomavirus vaccination programmes: a systematic review and meta-analysis

What explains anorectal chlamydia infection in women? Implications of a mathematical model for test and treatment strategies

Genital Chlamydia trachomatis: Understanding the Roles of Innate and Adaptive Immunity in Vaccine Research

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