Dr Nayomi Sanjeewa Danthanarayana
Consultant Medical Virologist
Teaching Hospital Karapitiya, Galle
Human papilloma virus
Human papilloma viruses (HPV) are small non-enveloped double standard DNA viruses belong to family Papovaviridae. They infect basal epithelial cells of skin and mucous membranes commonly causing viral warts. Majority of these infections are transient and clear within 12-24 months.
More than 200 different HPV types have been identified up to now and the number continues to expand. Out of them more than 40 types can infect the genital tract. Genital warts are usually transmitted during a sexual exposure although non-sexual infections also can occur. Based on their carcinogenic properties these types are divided in to two groups; high risk types and low risk types. The high-risk HPV types are the etiological agents of several cancers, such as those of the cervix, vagina, vulva, anus, penis, and a subset of head and neck cancers, particularly oropharyngeal cancer. Type 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59 and 66 are identified as the most common high-risk types to cause cervical cancer.
HPV and cancer
Cervical cancer is the second most common cause of cancer deaths worldwide and in Sri Lanka it is ranked as the second leading cause of female cancer deaths. Approximately 650 cervical cancer deaths occur annually in the country. High risk type HPV DNA is found to be positive in 99.7% of cervical cancer specimens. HPV type 16 and 18 are responsible for more than 70% of cervical cancers and are thought to be the most virulent out of all the carcinogenic types.
It is recognized that a well- organized cervical cancer screening programme can reduce cervical cancer and associated mortality. Despite marked advances in knowledge about cervical cancer and effective screening, cervical cancer screening programs have variable efficacy depending on availability of resources, implementation strategies, quality of laboratory and pathology testing, and community awareness.
Introduction of the HPV vaccine is thought to be another effective method to reduce the burden of cervical cancer. Statistical data from the recent years show that utilization of HPV vaccines is very effective for preventing infection and disease related to specific HPV genotypes.
HPV vaccines are intended to be administered if possible before the onset of sexual activity. There are three prophylactic vaccines available in the global market currently. These are, a bivalent vaccine against HPV16 and HPV18, a tetravalent vaccine against HPV6, 11, 16, and 18 and a 9-valent vaccine against HPV 6, 11, 16, 18, 31, 33, 45, 52, and 58. They are noninfectious subunit vaccines containing viral-like particles derived from recombinant DNA technology.
Administration of the vaccine is carried out by intramuscular injection with three doses over a 6 months period. Although both bivalent and tetravalent vaccines were originally licensed for a 3-dose immunization schedule, results of a systematic review indicate that 2 doses of HPV vaccine in girls aged 9–14 years are not inferior to 3 doses in terms of immunogenicity.
Bivalent HPV vaccine is indicated for use in females 9- 26 years of age and tetravalent HPV vaccine is indicated for use in both males and females 9-26 years. Nine valent vaccine is indicated in females 9 through 45 years of age for the prevention.
Early analysis shows that even a single dose can reduce infection and is effective in preventing the persistent incidence of infection and premalignant neoplasia. Strong and a long-lasting antibody response has been well documented with a seroconversion rate of almost 100% with antibody response remains stable for over a decade. HPV vaccines provide some cross-protection against HPV genotypes that are not included in the vaccines.
HPV vaccine in National Immunization Programme in Sri Lanka
HPV vaccine was introduced in the national immunization programme of Sri Lanka in July 2017 through school based vaccination programmes. Two doses of vaccines are given to 11-12 year old girls (in grade 6) with a minimum interval of 6 months. This is the tetravalent vaccine for HPV types 6,11,16, and 18. Both doses should be completed ideally before 13 years. Vaccine should be administered intramuscular preferably to the left upper deltoid region. HPV vaccine can be co-administered with aTd, inactivated hepatitis A and conjugate meningococcal vaccines but not described with influenza and MMR vaccines, so to keep 4-6 weeks gap when given. Adverse events are usually mild and transient. Should not vaccinate if allergy to any component in the vaccine or a severe allergic reaction to a previous HPV vaccine dose.
- Chan CK, Aimagambetova, G, Ukybassova, T, Kongrtay, K, Azizan, A. (2019) Human Papillomavirus Infection and Cervical Cancer: Epidemiology, Screening, and Vaccination-Review of Current Perspectives. J Oncol. 2019:3257939. doi: 10.1155/2019/3257939.
- Gheit T. (2019) Mucosal and Cutaneous Human Papillomavirus Infections and Cancer Biology. Front. Oncol. 9:355. doi: 10.3389/fonc.2019.00355
- ICO/IARC Information Centre on HPV and Cancer (HPV Information Centre) 2019. www.hpvcentre.net on 17 June 2019
- Ministry of Health, Nutrition and Indigenous Medicine. (2017) Guidelines on introduction of the human papillomavirus (HPV) vaccine into the national immunization programme. EPID/391/2017/VOL III
- Sri Lanka Medical Association. (2017) SLMA guidelines and information on vaccines. 6th edition
- WER. (2017). Human papillomavirus vaccines: WHO position paper, May 2017. No 19, 2017, 92, 241–268
- WHO. Human papillomavirus and HPV vaccines: a review. (2007) Cutts FT, Franceschi S, Goldie S, Castellsague X, de Sanjose S, Garnett G, Edmunds WJ, Claeys P, Goldenthal KL, Harperi DM, Markowitzj L. Bulletin of the World Health Organization September 2007, 85 (9). doi: 10.2471/BLT.06.038414