A groundbreaking study from Sweden offers powerful evidence for India's planned human papillomavirus (HPV) vaccination drive, demonstrating that high coverage not only protects vaccinated girls but also extends a shield of safety to unvaccinated women through herd protection. This finding is critical for a country where cervical cancer strikes 1.25 lakh women annually and claims 75,000 lives, standing as the second most common cancer among Indian women.
The Swedish Evidence: Herd Protection in Action
The research, which analysed pre-cancerous cervical lesions across different groups of women, provides a real-world model. It followed four cohorts born between 1989 and 2000. The earliest group (1989-1992) had access to subsidised vaccination, achieving only 25% coverage. The next (1993-1998) was eligible for catch-up jabs, reaching 55%. The most recent cohort (1999-2000) participated in a structured school-based programme, which successfully vaccinated 80% of the target group.
The results were striking. Unvaccinated women born in 1999 and 2000, who grew up surrounded by peers protected by the school programme, saw their risk of developing serious pre-cancerous cervical changes halved compared to unvaccinated women born a decade earlier. The incidence rates per 1,000 person-years dropped from 1.17 in the first cohort to 0.54 in the school-based programme cohort. Researchers highlighted this as a clear, real-world evaluation of the herd effect, where widespread immunisation disrupts the virus's circulation, benefiting everyone.
Why This is a Game-Changer for India's Public Health Strategy
India is on the cusp of a major public health initiative, aiming to vaccinate girls aged 9 to 14 through school-based programmes, later integrating the vaccine into routine immunisation. Dr. Neerja Bhatla, Professor and Head of Obstetrics and Gynaecology at AIIMS, explains the significance. While India lacks local herd immunity data due to limited vaccination so far, the global evidence is compelling. "Australia previously showed that after its HPV campaign, genital warts declined in both women and men. In the UK, pre-cancerous lesions were nearly eliminated in vaccinated cohorts," she notes.
The vaccine is most effective when administered before sexual debut, making the 9-14 age group ideal. Dr. Bhatla emphasises the coverage target: "A coverage of 90% among girls is desirable, but we need a coverage of at least 70% to generate meaningful herd protection for the wider population." The first signs of success will likely be a reduction in HPV infections and genital warts, with a decline in cancer incidence following years later.
Beyond Cervical Cancer: A Broader Shield Against Multiple Cancers
The benefits of high HPV vaccination coverage extend far beyond cervical cancer. Since HPV infection is also a known cause of cancers of the anus, vagina, and oropharynx (part of the throat), a successful immunisation drive is projected to lower the incidence of these cancers as well.
Furthermore, a significant positive side-effect will be a reduced burden on the healthcare system's diagnostic resources. "When HPV incidence goes down, the requirement for triage tests like biopsy and CIN tests to confirm cancer will also reduce," Dr. Bhatla points out. This would free up crucial medical infrastructure and resources.
The quadrivalent vaccines, including the one manufactured by the Serum Institute of India, protect against HPV types 16, 18, 6, and 11. Types 16 and 18 alone are responsible for approximately 70% of global cervical cancer cases. By blocking these high-risk strains, the vaccine acts as a primary prevention tool, stopping infection before it can lead to warts or cancer.
The Swedish study serves as a robust blueprint, underscoring that a determined, high-coverage school-based vaccination programme is not just an individual safeguard but a transformative, cost-effective public health strategy to protect entire generations of women.
