In 2008, India faced an estimated 134,000 new cervical cancer cases and 73,000 deaths. HPV vaccines offered protection but required three doses, increasing costs and delivery demands. For CFI, joining research into fewer doses meant addressing a question central to prevention: could protection become affordable and achievable for more girls in LMICs like India?

CFI coordinated with the Governments of Sikkim and Mizoram to build cohorts of a multicentre Indian study led by the International Agency for Research on Cancer, WHO’s cancer agency. Around 1,000 adolescent girls from these states participated, bringing Northeast Indian communities into an international effort to establish how much vaccination was needed for lasting protection.

The study began in 2009, initially comparing two doses with three. When HPV vaccination in research studies was halted nationally in 2010, participants had received different numbers of doses. The research continued as an observational study, allowing scientists to compare protection after one, two and three doses over time.

Across 15 years, CFI sustained field coordination and follow-up as adolescent participants became adults. Participants gave fresh informed consent upon adulthood. The wider study’s protocol required annual contact, updated participant information, repeated cervical sampling when eligible and screening from age 25. Such continuity connected community participation with the clinical observations needed to assess whether vaccine protection endured.

The 2024 publication reported 92% efficacy against persistent HPV16 and HPV18 infection after a single dose, comparable to two or three doses. No high-grade cervical precancers associated with these types were detected among vaccinated participants, compared with eight among unvaccinated women. With median follow-up of 12 years, the findings demonstrated protection extending up to 15 years after vaccination.

These results strengthened international confidence in simpler schedules, building on earlier evidence supporting two doses and WHO’s 2022 single-dose recommendation. Fewer doses can reduce vaccination costs, repeat visits and delivery pressures, helping health systems extend protection with available resources.

For the girls and families in Sikkim and Mizoram, participation became a contribution to knowledge reaching far beyond their states. CFI’s sustained involvement helped carry their experience into a shared evidence base, linking local commitment with a lasting change in the possibilities for cervical cancer prevention worldwide.