Efficacy of HPV Immunization Amongst Adolescent Girls Within UK
Introduction: Human papilloma virus is the most common sexual transmitted virus in the U.K. More than 4 types of HPV variants, is found to infect both men and women. Genital areas, mouth and throat are commonly affected by the virus. The virus can be transmitted by intercourse between same sex and straight sex partners. Very rarely, the disease is transmitted from the pregnant mother to the baby. The virus has the potential to cause cancer and presently there is no cure for HPV infection. Among HPV types: HPV16 and 18 are highly oncogenic. FDA approved HPV vaccines are available in the market for use in male and females aged 9-26 years. These vaccines are expected to reduce the incidence of HPV positive cytology for invasive cervical cancer. When compared to older women, adolescent girls in the age group 12-16 years produce a higher titer of antibodies following immunization, and this is a favorable for preventing the disease. In this paper, we critically appraise research articles that evaluate the efficacy of HPV immunization among adolescent girls in the U.K. (National Cancer Institute, 2016) The three theme that emerged from the literature review are: immunization coverage, prevalence of HPV infection and screening for HPV post vaccination. (Adams, Jasani and Fiander, 2007)
Critical Review:
1. In the study title, Uptake of first two doses of human papillomavirus vaccine by adolescent schoolgirls in Manchester: prospective cohort study, the authors Barbin et al., assesses the feasibility and acceptability of HPV vaccination of adolescent girls in Manchester U.K. From, 2008, HPV vaccination was established as routine for girls aged 12 to 13 years of age in the U.K. The quadrivalent vaccine (Gardasil; Merck, PA, USA) and a bivalent vaccine (Cervarix; GlaxoSmithKline, Rixensart, Belgium), were licensed for use in U.K. These two vaccines can effectively prevent HPV-16 and HPV-18 infections. The success of a national immunization program for HPV, will depend on the extent of adolescent girls covered by immunization. The vaccination protocol requires that the adolescent is vaccinated with three doses of vaccine at 0, 1 and 6 months’ interval within a year. (Brabin et al., 2008)
Using a prospective cohort design, the researchers studied the rate of acceptance for the 1st and 2nd dose of the HPV vaccine. The study was conducted in 36 secondary schools in Great Manchester. The number of school girls aged 12-13 years, who participated in the study was 2817. The method of sampling adopted in area wise sampling specific to Manchester. The number of students who reported for the 1st and 2nd dose of vaccine was recorded. Only 70.6% of the participants reported for the first vaccination. The number of participants who reported for the second dose reduced to 68.5%. Though there has been a sizable coverage, close to ~29% of the girls remain unvaccinated. The rate of non-vaccination was high among ethical minorities. The lack of proper information, and fear of long term side effects associated with vaccination, were identified as the main factor that discouraged parents from approving the vaccination of their children. (Brabin et al., 2008)
2. In the research article titled, Prevalence of human papillomavirus (HPV) infections in sexually active adolescents and young women in England, prior to widespread HPV immunization, presents the prevalence rate of HPV infection among young female population in U.K prior to 2008. The HPV mass immunization program was instituted in 2008. The prevalence level prior to 2008, will act as a baseline against which the effectiveness of immunization can be compared.
Method: A total of 3829 sexually active women aged 13 to 24 years of age participated in this study. The method of sampling is not strictly random. It is more like convenient sampling. A majority of the women were above 16 years of age and only 275 females were in the age group of 13 -15 years of age. The study also examined the association between prevalence rate and sexual activity. (Howell-Jones et al., 2012)
The findings of the study, suggests a higher prevalence of HPV infection prior to 2008. The prevalence rate was higher in women, who has more than one sexual partner. The prevalence was ~ 35% in women aged 16-24 years of age. About 50% of the women in this study, had multiple sexual partners. (Howell-Jones et al., 2012)
3. The research article titled, Estimating the long-term impact of a prophylactic human papillomavirus 16/18 vaccine on the burden of cervical cancer in the UK, was a bioinformatics study that was designed to predict the impact of HPV vaccination on cervical cancer in U.K. A mathematical model was developed, based the screening results obtained from other countries in the world. This model was applied to U.K vaccination program. The mathematical model was based on published data, on the impact of HPV immunization on reduction of cervical cancer. According to this estimate, HPV vaccination can reduce cervical cancer by 66% and cervical cancer deaths by 76%. These results, forecast a sizeable amount of reduction in risk and mortality associated with cervical cancer in U.K (Kohli et al., 2006).
The bi-valent HPV-16/18 vaccine is more than 95% effective against the persistent HPV-16 and 18 strains (Baylor, 2009). The protection offered by bivalent vaccine, last for 4.5 years. HPV-16 and HPV-18 accounts for 70% of the cervical papilloma infections, globally (Baylor, 2009). In the absence of any published work on the effectiveness of vaccination in U.K, this prediction based on the estimates in other countries, is the only source of information on vaccine efficacy.
Conclusion: HPV vaccination can benefit the U.K population by offering protection from invasive infection caused by HPV. Though U.K has achieved a significant coverage in its mass immunization program, there is still a lot of people who are not vaccinated and can remain a threat for others. The information on the current prevalence of HPV is not known. The impact of HPV vaccination in preventing cervical cancer, needs to be validated.
References
Adams, M., Jasani, B. and Fiander, A. (2007). Human papilloma virus (HPV) prophylactic vaccination: Challenges for public health and implications for screening. Vaccine, 25(16), pp.3007-3013.
Baylor, N. (2009). Efficacy Data and HPV Vaccination Studies. JAMA, 302(24), p.2658.
Brabin, L., Roberts, S., Stretch, R., Baxter, D., Chambers, G., Kitchener, H. and McCann, R. (2008). Uptake of first two doses of human papillomavirus vaccine by adolescent schoolgirls in Manchester: prospective cohort study. BMJ, 336(7652), pp.1056-1058.
Howell-Jones, R., de Silva, N., Akpan, M., Oakeshott, P., Carder, C., Coupland, L., Sillis, M., Mallinson, H., Ellis, V., Frodsham, D., Robinson, T., Gill, O., Beddows, S. and Soldan, K. (2012). Prevalence of human papillomavirus (HPV) infections in sexually active adolescents and young women in England, prior to widespread HPV immunisation. Vaccine, 30(26), pp.3867-3875.
National Cancer Institute. (2016). Human Papillomavirus (HPV) Vaccines. [online] Available at: http://www.cancer.gov/about-cancer/causes-prevention/risk/infectious-agents/hpv- vaccine-fact-sheet [Accessed 30 May 2016].
Kohli, M., Ferko, N., Martin, A., Franco, E., Jenkins, D., Gallivan, S., Sherlaw-Johnson, C. and Drummond, M. (2006). Estimating the long-term impact of a prophylactic human papillomavirus 16/18 vaccine on the burden of cervical cancer in the UK. Br J Cancer, 96(1), pp.143-150.
