There are over a hundred strains of HPV, and not all of them cause cancer. Currently, 14 strains are known to cause cancer, in particular HPV type 16 and 18 which are responsible for 70% of cervical cancer and pre-cancerous lesions. Some other cancer-causing strains include 31, 33, 45, 52, 58 and more. On the other hand, 90% of genital warts are caused by HPV type 6 and 11, which rarely develop into cancer. While different types of vaccines protect against different numbers of HPV types, one thing is for sure—they all have the majority-cancer-causing type 16 and 18 in common.
Considering that most sexually active people get infected at some point in their lives, this effectively means that HPV vaccines work best when administered before the individual has begun engaging in any sexual activity. Nonetheless, those who are sexually active and may have already been exposed to some strains of HPV may still find benefit in receiving the HPV vaccine (assuming eligibility criteria are met), because it is unlikely that they have already contracted all the strains that some of these vaccines protect against. While long-term studies of vaccine efficacy are still in progress to better understand the full duration of protection conferred, current evidence shows a sustained protection against vaccine-targeted HPV-related diseases; and there is currently no recommendation for booster shots or extra doses.
There are 3 types of HPV vaccines available: Gardasil 9 (the newest), Gardasil 4 and Cervarix; and they are offered to women and girls from age 9 onwards. Younger teens and adolescents between 9-14 years of age only need to have 2 injections, whereas 3 injections are required for age 15 and older. Women up to age 45 are licensed to have the vaccine but older women may also benefit.
|Gardasil 9||HPV Types 6, 11, 16, 18, 31, 33, 45, 52, 58|
|Gardasil 4||HPV Types 6, 11, 16, 18|
|Cervarix||HPV Types 16, 18|
To that end, he serves on the board of the International Federation of Colposcopy & Cervical Pathology, and his extensive research and humanitarian work centre around HPV and cervical cancer as well.