🦠 Herd Protection from Vaccinating Boys Simulator

Girls-Only Vaccination Leaves a Transmission Gap

Vaccinating only girls still leaves boys as an active HPV reservoir.

• 0%: Male coverage (no boys vaccinated)
• ~80%: Female coverage (typical target)
• 9: HPV types covered (in nonavalent vaccine)
• rising: Male HPV cancers (oropharyngeal, anal)

Girls-first strategy rationale

Cervical cancer burden made girls the first priority.

The circulation gap

Unvaccinated boys keep passing HPV through the population.

Limits of one-sided coverage

Herd effects stall once male transmission stays unchecked.

Gender-Neutral Vaccination Adds Boys to the Program

Public health programs expand HPV vaccination to include boys directly.

• 50+: Countries with GNV (gender-neutral programs)
• ~35%: Male coverage target (early rollout stage)
• 2–3: Vaccine doses (age-dependent schedule)
• 11–12: Typical age (recommended start)

Why include boys

Boys benefit directly and reduce spread to others.

Rollout logistics

School-based programs extend easily to both sexes.

Early coverage curve

Male uptake starts lower than established female programs.

Vaccinated Boys Transmit HPV Far Less Often

Vaccinated males acquire and shed HPV at sharply lower rates.

• ~65%: Male coverage (mid-rollout)
• ~90%: Infection reduction (vaccine-type HPV)
• falling: Transmission chains (fewer active carriers)
• high: Efficacy in males (per clinical trials)

Blocking acquisition

Vaccination prevents infection before it can spread further.

Fewer carriers

Each vaccinated male removes a transmission link.

Network effect

Removing links breaks longer chains of spread.

Community HPV Prevalence Declines Across the Population

Rising joint coverage drives overall community HPV prevalence downward.

• ~85%: Male coverage (near-mature program)
• steep: Prevalence drop (population-level decline)
• down: Genital warts (early sentinel indicator)
• yes: Both sexes covered (compounding effect)

Compounding coverage

Male and female coverage together suppress circulation fastest.

Sentinel signals

Genital wart rates fall first and fastest.

Approaching elimination

High dual coverage pushes prevalence toward near-zero.

Unvaccinated Individuals Gain Indirect Protection

Reduced community circulation shields people who were never vaccinated.

• ~96%: Male coverage (mature program)
• strong: Indirect protection (unvaccinated benefit)
• >90%: Population protected (combined direct+indirect)
• declining: Cancer trajectory (long-term projection)

Herd protection mechanism

Fewer carriers means less exposure risk for everyone.

Equity gains

Unvaccinated and under-vaccinated groups still benefit.

Long-term outlook

Sustained dual coverage moves toward HPV elimination.