Human papillomavirus (HPV) is a virus from the papillomavirus family that is capable of infecting humans. Like all papillomaviruses, HPVs establish productive infections only in keratinocytes of the skin or mucous membranes, making it easily transmitted sexually or through other intimate contact. While the majority of the known types of HPV cause no symptoms in most people, some types can cause warts (verrucae). HPV types 16 and 18 cause approximately 70% of cervical cancers, and cause most HPV-induced anal, vulvar, vaginal, and penile cancers. The HPV quadrivalent vaccine, also known as Gardasil (or Silgard in Europe), is marketed by Merck. The vaccine prevents the transmission of certain types of HPV, specifically types 6, 11, 16 and 18.
Setting aside all of the scientific lingo, HPV infections are closely linked with many dangerous cancers, and it is generally the major (if not only) cause of almost all of those cancers.
Although the safety of HPV vaccine has been thoroughly vetted for safety in studies with large cohorts (which, in analysis of nearly 200,000 women who received the vaccine in a controlled setting, there were NO observed significant adverse events), the long time period (up to decades) from infection to a diagnosis of an HPV-related cancer has left questions about how to maximize effectiveness of the vaccine which required further research.
A new study examining the rate of HPV infections in young Australians after the introduction of the HPV vaccine shows a significant decline in HPV infections in this group. Moreover, there was no observed HPV infections in women who were vaccinated, which provides more evidence of the high efficacy of the vaccine.
The study examined nearly 86,000 Australian born patients, comparing a group from the pre-vaccination period (2004 through mid-2007) and the vaccination period (mid-2007 through the end of 2011). Of all of the participants in the study, 7686 (or about 9.0%) were found to have genital warts.
The results of the study were dramatic:
- For under 21 year old women, those diagnosed with genital warts declined from 11.5% in 2007 (pre-vaccination period) to 0.85% in 2011. Statistical significance is P<0.001 (strongly significant).
- For women between 21 and 30 years old, those diagnosed with genital warts declined from 11.3% in 2007 to 3.1% in 2011. Same level of statistical significance.
- For women over 30 years of age, there was no significant decline in genital wart diagnoses, probably since many had already contracted the disease prior to vaccination.
- For men under 21 years old, those diagnosed with genital warts declined from 12.1% in 2007 to 2.2% in 2011, again P<0.001.
- For men between 21 and 30 years old, diagnoses dropped from 18.2% in 2007 to 8.9% in 2011, again statistically significant at P<0.001.
- Like women over 30, the same group of men showed no significant decline in genital warts.
In 2007, Australia became one of the first countries to implement a nationally funded program of HPV vaccinations for girls and young women. The program offers free vaccination to girls between the ages of 12 and 13 in schools. Additionally, between 2007 and 2009, Australia offered two “catch-up” vaccination programs one for 13-18 year olds in school, and the other for 18-26 year old women out of school. Few men were vaccinated, so the drop in genital warts is probably a result of the herd immunity as the infection rate in women drops.
Furthermore, in 2011, none of the vaccinated women under 21 were diagnosed with genital warts. In the same year, 7 per cent of unvaccinated women under 21 (out of 161) were diagnosed with genital warts.
The authors concluded that:
The significant declines in the proportion of young women found to have genital warts and the absence of genital warts in vaccinated women in 2011 suggests that the human papillomavirus vaccine has a high efficacy outside of the trial setting. Large declines in diagnoses of genital warts in heterosexual men are probably due to herd immunity.
Let’s give Australia a standing ovation for saving the lives of their children! Because vaccines do save lives.
- Ali H, Donovan B, Wand H, Read TR, Regan DG, Grulich AE, Fairley CK, Guy RJ. Genital warts in young Australians five years into national human papillomavirus vaccination programme: national surveillance data. BMJ. 2013 Apr 18;346:f2032. doi: 10.1136/bmj.f2032. PubMed PMID: 23599298.
- John TJ, Samuel R. Herd immunity and herd effect: new insights and definitions. Eur J Epidemiol. 2000;16(7):601-6. Review. PubMed PMID: 11078115.
- Klein NP, Hansen J, Chao C, Velicer C, Emery M, Slezak J, Lewis N, Deosaransingh K, Sy L, Ackerson B, Cheetham TC, Liaw KL, Takhar H, Jacobsen SJ. Safety of quadrivalent human papillomavirus vaccine administered routinely to females. Arch Pediatr Adolesc Med. 2012 Dec;166(12):1140-8. doi: 10.1001/archpediatrics.2012.1451. PubMed PMID: 23027469.