Mathematical model for the natural history of human papillomavirus infection and cervical carcinogenesis

Immigrant women's experiences and views on the prevention of cervical cancer: a qualitative study

BACKGROUND

Many Western countries have cervical cancer screening programmes and have implemented nation-wide human papillomavirus (HPV) vaccination programmes for preventing cervical cancer.

OBJECTIVE

To explore immigrant women's experiences and views on the prevention of cervical cancer, screening, HPV vaccination and condom use.

DESIGN

An exploratory qualitative study. The Health Belief Model (HBM) was used as a theoretical framework.

SETTING AND PARTICIPANTS

Eight focus group interviews, 5-8 women in each group (average number 6,5), were conducted with 50 women aged 18-54, who studied Swedish for immigrants. Data were analysed by latent content analysis.

RESULTS

Four themes emerged: (i) deprioritization of women's health in home countries, (ii) positive attitude towards the availability of women's health care in Sweden, (iii) positive and negative attitudes towards HPV vaccination, and (iv) communication barriers limit health care access. Even though the women were positive to the prevention of cervical cancer, several barriers were identified: difficulties in contacting health care due to language problems, limited knowledge regarding the relation between sexual transmission of HPV and cervical cancer, culturally determined gender roles and the fact that many of the women were not used to regular health check-ups.

CONCLUSION

The women wanted to participate in cervical cancer prevention programmes and would accept HPV vaccination for their daughters, but expressed difficulties in understanding information from health-care providers. Therefore, information needs to be in different languages and provided through different sources. Health-care professionals should also consider immigrant women's difficulties concerning cultural norms and pay attention to their experiences.

Economic evaluation of DNA ploidy analysis vs liquid-based cytology for cervical screening

Background:

DNA ploidy analysis involves automated quantification of chromosomal aneuploidy, a potential marker of progression toward cervical carcinoma. We evaluated the cost-effectiveness of this method for cervical screening, comparing five ploidy strategies (using different numbers of aneuploid cells as cut points) with liquid-based Papanicolaou smear and no screening.

Methods:

A state-transition Markov model simulated the natural history of HPV infection and possible progression into cervical neoplasia in a cohort of 12-year-old females. The analysis evaluated cost in 2012 US$ and effectiveness in quality-adjusted life-years (QALYs) from a health-system perspective throughout a lifetime horizon in the US setting. We calculated incremental cost-effectiveness ratios (ICERs) to determine the best strategy. The robustness of optimal choices was examined in deterministic and probabilistic sensitivity analyses.

Results:

In the base-case analysis, the ploidy 4 cell strategy was cost-effective, yielding an increase of 0.032 QALY and an ICER of $18 264/QALY compared to no screening. For most scenarios in the deterministic sensitivity analysis, the ploidy 4 cell strategy was the only cost-effective strategy. Cost-effectiveness acceptability curves showed that this strategy was more likely to be cost-effective than the Papanicolaou smear.

Conclusion:

Compared to the liquid-based Papanicolaou smear, screening with a DNA ploidy strategy appeared less costly and comparably effective.

Cost effectiveness of human papillomavirus-16/18 genotyping in cervical cancer screening

BACKGROUND

There is limited understanding of the health economic implications of cervical screening with human papillomavirus (HPV)-16/18 genotyping.

OBJECTIVE

The aim of this study was to evaluate the cost effectiveness of cervical cancer primary screening with a HPV-16/18 genotyping test which simultaneously detects 12 other high-risk HPV types.

METHODS

A Markov cohort model compared four strategies: (1) cytology with reflex HPV testing for atypical squamous cells of undetermined significance (ASC-US); (2) co-testing with cytology and HPV testing; (3) HPV with reflex to cytology; and (4) HPV with 16/18 genotyping and reflex cytology (ASC-US threshold). Screening began at age 30 and was performed triennially over 40 years. Screening sensitivity and specificity values for cervical intraepithelial neoplasia (CIN) 3 were obtained from the Addressing THE Need for Advanced HPV Diagnostics (ATHENA) trial. Outcomes for a 1-year follow-up scenario wherein persistent disease was detected were estimated. Screening and cancer treatment costs were calculated from a US payer's perspective in 2013. Costs and quality-adjusted life-years (QALYs) were discounted at 3 % annually.

RESULTS

Applying a US$50,000/QALY threshold, strategy (4) dominated strategies (2) and (3) by reducing costs and cancer incidence and improving QALYs, and was cost effective versus strategy (1). Accounting for persistent ≥CIN 3 at 1 year, strategy (4) was cost effective versus all other strategies. Detecting HPV-16/18 resulted in earlier diagnosis of clinically relevant ≥CIN 3 at initial screening and efficient use of follow-up resources. Outcomes were most influenced by strategy performance.

CONCLUSIONS

Incorporating HPV-16/18 genotyping is cost effective and may improve detection of CIN, thereby preventing cervical cancer.

Cost-effectiveness of a bivalent human papillomavirus vaccination program in Japan

Background Human papillomavirus (HPV) vaccines and their widespread adoption have the potential to relieve a large part of the burden of cervical cancer morbidity and mortality, particularly in countries that have low screening rates or, like Japan, lack a cohesive universal screening program. An economic evaluation was conducted to assess the cost-effectiveness of introducing a bivalent HPV vaccination program in Japan from a healthcare perspective. Methods: A Markov model of the natural history of HPV infection that incorporates both vaccination and screening was developed for Japan. The modelled intervention, a bivalent HPV vaccine with a 100% lifetime vaccine efficacy and 80% vaccine coverage, given to a cohort of 12-year-old Japanese girls in conjunction with the current screening program, was compared with screening alone in terms of costs and effectiveness. A discount rate of 5% was applied to both costs and utilities where relevant. Results: Vaccination alongside screening compared with screening alone is associated with an incremental cost-effectiveness ratio (ICER) of US$20 315 per quality-adjusted-life-year gained if 80% coverage is assumed. The ICER at 5% coverage with the vaccine plus screening, compared with screening alone, is US$1158. Conclusion: The cost-effectiveness results suggest that the addition of a HPV vaccination program to Japan’s cervical cancer screening program is highly likely to prove a cost-effective way to reduce the burden of cervical cancer, precancerous lesions and HPV16/18-related diseases.

The Effectiveness of a Facebook-Assisted Teaching Method on Knowledge and Attitudes About Cervical Cancer Prevention and HPV Vaccination Intention Among Female Adolescent Students in Taiwan

BACKGROUND

Lack of education is a known barrier to vaccination, but data on the design and effectiveness of interventions remain limited.

OBJECTIVE

This study aims to identify the effectiveness of a Facebook-assisted teaching method on female adolescents' knowledge and attitudes about cervical cancer prevention and on their human papillomavirus vaccination intention.

METHOD

A quasi-experimental time series research design was used. Two hundred female adolescents at a senior high school in Taipei were recruited into two groups. Following a classroom lecture, one group was provided a Facebook-assisted online discussion, and the other group was provided an in-person discussion forum. A demographic questionnaire and cervical cancer prevention questionnaire were distributed. Data were analyzed for descriptive statistics and generalized estimation equations.

RESULTS

Improvement from T0 to T2 in knowledge and attitude scores was 4.204 and 4.496 points, respectively. The Facebook group's improvement in vaccination intention from T0 to T2 was 2.310 times greater than the control group's improvement under conditions of out-of-pocket expenses and 2.368 times greater under conditions of free vaccination.

CONCLUSIONS

School-based cervical cancer prevention education can be effective. The Facebook-assisted discussion method was more effective than the in-person discussion. Providing the human papillomavirus vaccine free of charge would increase female adolescents' intention to be vaccinated.

Clinical effectiveness and cost-effectiveness of quadrivalent human papillomavirus vaccination in HIV-negative men who have sex with men to prevent recurrent high-grade anal intraepithelial neoplasia

We examined the long-term clinical and economic benefits of quadrivalent human papillomavirus (qHPV) vaccine as a secondary/adjunct prevention strategy in the prevention of recurrent high-grade intraepithelial neoplasia (HGAIN) in HIV-negative men who have sex with men (MSM) and are 27 years or older. We constructed a Markov model to evaluate the clinical effectiveness and cost-effectiveness of two strategies: (1) no qHPV vaccine after treatment for HGAIN versus (2) qHPV vaccine after treatment for HGAIN. Model parameters, including natural history of anal cancer, vaccine efficacy measured in terms of hazard ratio (HR) (decrease in the risk of recurrent HGAIN), HGAIN treatment efficacy, utilities, and costs, were obtained from the literature. The outcomes were measured in terms of lifetime risk of anal cancer, lifetime cost, quality-adjusted life years, and incremental cost-effectiveness ratios (ICERs). Sensitivity analysis was conducted on all model parameters. We found that vaccinating HIV-negative MSM reduced the lifetime risk of anal cancer by 60.77% at an ICER of US$87,240 per quality-adjusted life-year. The results were highly sensitive to vaccine efficacy, transition of HGAIN to anal cancer, cost of treatment for HGAIN, vaccine degree of protection over time, and the vaccine duration of protection and less sensitive to HPV clearance, cost of qHPV vaccine, and the transitions from normal to low-grade anal intraepithelial neoplasia (LGAIN) and normal to HGAIN. With an HR of 0.3, the ICER was well below a $50,000 willingness-to-pay threshold; with an HR of 0.5, the ICER was still below a threshold of $100,000. The most critical disease-related factor influencing the cost-effectiveness was the progression of HGAIN to anal cancer. At an annual transition probability below 0.001, the ICER was below $50,000. Vaccinating HIV-negative MSM treated for HGAIN decreases the lifetime risk of anal cancer and is likely to be a cost-effective intervention.

DYNAMICS ANALYSIS OF A VACCINATION MODEL FOR HPV TRANSMISSION

A new deterministic model for the transmission dynamics of human papillomavirus (HPV) and related cancers, in the presence of the Gardasil vaccine (which targets four HPV types), is presented. In the absence of routine vaccination in the community, the model is shown to undergo the phenomenon of backward bifurcation. This phenomenon, which has important consequences on the feasibility of effective disease control in the community, arises due to the re-infection of recovered individuals. For the special case when backward bifurcation does not occur, the disease-free equilibrium (DFE) of the model is shown to be globally-asymptotically stable (GAS) if the associated reproduction number is less than unity. The model with vaccination is also rigorously analyzed. Numerical simulations of the model with vaccination show that, with the assumed 90% efficacy of the Gardasil vaccine, the effective community-wide control of the four Gardasil-preventable HPV types is feasible if the Gardasil coverage rate is high enough (in the range 78–88%).

Ethnic and gender differences in HPV knowledge, awareness, and vaccine acceptability among White and Hispanic men and women

The purpose of this study was to examine factors associated with human papillomavirus (HPV) knowledge and awareness, and HPV vaccination among White and Hispanic males and females. Differences in HPV knowledge, sources of information, vaccine awareness, vaccination status, and interest in vaccination were examined. A community sample was recruited from local health care clinics in a medium sized Midwestern city between May 2010 and December 2011. Participants (N = 507) were White (n = 243) and Hispanic, males (n = 202) and females between the ages of 15-30. Results indicate that White and female participants were significantly more likely to have heard of HPV, have higher levels of HPV knowledge, have been diagnosed with HPV, and be aware of the HPV vaccine for women. White and female participants were also more likely to have heard of HPV from their physician and were significantly more interested in receiving the HPV vaccine in the future. There was no effect of ethnicity on interest in the vaccine per a doctor's recommendation, however. Findings suggest that Whites and females have greater levels of HPV awareness and knowledge and that, while Hispanic participants are less likely than White participants to be told about the HPV vaccine from their provider, they may be equally receptive to such a recommendation.

[Proven and new methods in the treatment of genital warts]

Anogenital warts are the most common clinical manifestation of human papillomavirus (HPV) infections. Although easy to recognize, asymptomatic anogenital warts (condylomata acuminata) may be overlooked, leading to unaware transmission to the sexual partner. On the other hand awareness of this sexually transmitted disease (STD) is largely associated with a great psychological and social burden, in men as well as women. Spontaneous regression of genital warts has been observed mostly within 2-5 years; however, persisting condylomata may prove refractory to all current treatment options. Because removal of the warts does not totally eliminate the underlying viral infection, treatment of genital warts can often be of long duration, of varying effectiveness and with high recurrence rates. Without a doubt only the patient's own immune system is capable of clearing HPV infections. Therefore, the solution to one of mankind's oldest health problems will depend on the future acceptability of HPV vaccines.

Impact of the National Breast and Cervical Cancer Early Detection Program on cervical cancer mortality among uninsured low-income women in the U.S., 1991-2007

BACKGROUND

The benefits of the National Breast and Cervical Cancer Early Detection Program (NBCCEDP) on cervical cancer screening for participating uninsured low-income women have never been measured.

PURPOSE

To estimate the benefits in life-years (LYs) gained; quality-adjusted life-years (QALYs) gained; and deaths averted.

METHODS

A cervical cancer simulation model was constructed based on an existing cohort model. The model was applied to NBCCEDP participants aged 18-64 years. Screening habits for uninsured low-income women were estimated using National Health Interview Survey data from 1990 to 2005 and NBCCEDP data from 1991 to 2007. The study was conducted during 2011-2012 and covered all 68 NBCCEDP grantees in 50 states, the District of Columbia, five U.S. territories, and 12 tribal organizations. Separate simulations were performed for the following three scenarios: (1) women who received NBCCEDP (Program) screening; (2) women who received screening without the program (No Program); and (3) women who received no screening (No Screening).

RESULTS

Among 1.8 million women screened in 1991-2007, the Program added 10,369 LYs gained compared to No Program, and 101,509 LYs gained compared to No Screening. The Program prevented 325 women from dying of cervical cancer relative to No Program, and 3,829 relative to No Screening. During this time period, the Program accounted for 15,589 QALYs gained when compared with No Program, and 121,529 QALYs gained when compared with No Screening.

CONCLUSIONS

These estimates suggest that NBCCEDP cervical cancer screening has reduced mortality among medically underserved low-income women who participated in the program.

An updated natural history model of cervical cancer: derivation of model parameters

Mathematical models of cervical cancer have been widely used to evaluate the comparative effectiveness and cost-effectiveness of preventive strategies. Major advances in the understanding of cervical carcinogenesis motivate the creation of a new disease paradigm in such models. To keep pace with the most recent evidence, we updated a previously developed microsimulation model of human papillomavirus (HPV) infection and cervical cancer to reflect 1) a shift towards health states based on HPV rather than poorly reproducible histological diagnoses and 2) HPV clearance and progression to precancer as a function of infection duration and genotype, as derived from the control arm of the Costa Rica Vaccine Trial (2004-2010). The model was calibrated leveraging empirical data from the New Mexico Surveillance, Epidemiology, and End Results Registry (1980-1999) and a state-of-the-art cervical cancer screening registry in New Mexico (2007-2009). The calibrated model had good correspondence with data on genotype- and age-specific HPV prevalence, genotype frequency in precancer and cancer, and age-specific cancer incidence. We present this model in response to a call for new natural history models of cervical cancer intended for decision analysis and economic evaluation at a time when global cervical cancer prevention policy continues to evolve and evidence of the long-term health effects of cervical interventions remains critical.

Development of a quality framework for models of cervical screening and its application to evaluations of the cost-effectiveness of HPV vaccination in developed countries

BACKGROUND

HPV vaccination has now been introduced in most developed countries, but this has occurred in the context of established cervical cancer screening mechanisms which provide population-level protection against the most common HPV-related cancer. Therefore, estimating the cost-effectiveness of HPV vaccination to further reduce HPV-related disease depends in large part on the estimation of the effectiveness of the cervical screening 'background'. The aim of this study was to systematically review and assess methods for simulating cervical screening in decision analytic models used for evaluation of HPV vaccination.

METHODS

Existing quality frameworks for economic models were extended to develop a specific quality framework for models of cervical screening. This involved domains for model structure, parameterisation (data sources) and validation (consistency). A systematic review of economic evaluations of HPV vaccination was then conducted, and assessment of cervical screening model components was then performed via application of the new quality framework.

RESULTS

Generally, models took into account population-level cervical screening participation, but were inconsistent in their approach to modelling abnormal smear management, diagnostic evaluation and treatment of precancerous disease. There was also considerable variability in the accuracy of modelling clinical pathways and the scope of validation performed for screening-related outcomes, with focus directed towards cervical cancer targets. Only a few models comprehensively validated against observed pre-cancerous abnormalities.

CONCLUSION

Models of HPV vaccination in developed countries can be improved by further attention to the 'background' modelling of secondary protection via cervical screening. The quality framework developed for this review can be used to inform future HPV vaccination evaluations, including evaluations of the cost-effectiveness of male vaccination and next generation HPV vaccines, and to assess models used to evaluate new cervical screening technologies and recommendations.

Natural history of anal dysplasia in an HIV-infected clinical care cohort: estimates using multi-state Markov modeling

OBJECTIVES

(1) To model the natural history of anal neoplasia in HIV-infected patients using a 3-state Markov model of anal cancer pathogenesis, adjusting for cytology misclassification; and (2) to estimate the effects of selected time-varying covariates on transition probabilities.

DESIGN

A retrospective cytology-based inception screening cohort of HIV-infected adults was analyzed using a 3-state Markov model of clinical pathogenesis of anal neoplasia.

METHODS

Longitudinally ascertained cytology categories were adjusted for misclassification using estimates of cytology accuracy derived from the study cohort. Time-varying covariate effects were estimated as hazard ratios.

RESULTS

(1) There was a moderate to high probability of regression of the high grade squamous intraepithelial lesion (HSIL) state (27-62%) at 2 years after initial cytology screening; (2) the probability of developing invasive anal cancer (IAC) during the first 2 years after a baseline HSIL cytology is low (1.9-2.8%); (3) infrared coagulation (IRC) ablation of HSIL lesions is associated with a 2.2-4.2 fold increased probability of regression to <HSIL; and (4) antiretroviral therapy, suppressed HIV plasma viral load, and CD4 ≥350/mm3 are each associated with reduced probability of progression from <HSIL to HSIL.

CONCLUSIONS

The finding of moderate to high rates of regression of the HSIL state accompanied by low rates of progression to IAC should inform both screening and precursor treatment guideline development. There appears to be a consistent and robust beneficial effect of antiretroviral therapy, suppressed viral load, and higher CD4 on the transition from the <HSIL state to the HSIL state.

Perceptions of and preferences for federally-funded family planning clinics

BACKGROUND

The Title X family planning program provides affordable access to a range of sexual and reproductive health services, with a priority for low-income people. The disproportionate burden of unintended pregnancy, breast and cervical cancer, and sexually transmitted diseases among minority groups, teens, and young adults in the US underscore the need for affordable access to such services. However, increased access to sexual and reproductive health services, resulting from the Affordable Care Act (ACA) create questions regarding the continued need for this program.

METHODS

A study was conducted to assess clients' perceptions of Title X-funded family planning clinics and their preferences for these clinics for a range of sexual and reproductive health services. An anonymous, self-administered, paper-and-pencil survey was administered to 696 clients who received services from one of eight Title X-funded family planning clinics in Northeast Ohio.

RESULTS

The majority of participants stated very positive perceptions of the Title X-funded clinics; that they "Always" go to the Title X-funded clinic for birth control, STD/HIV testing, and pregnancy testing; and that the Title X-funded clinic was their regular source of health care. Females were more likely than males to prefer the Title X clinic for birth control, physical exams, pregnancy testing, and health information and more teens under the age of 18 preferred to use the Title X clinic for STD/HIV testing, physical exams, pregnancy testing, and health information.

CONCLUSIONS

Findings indicate that these Title X-funded family planning clinics successfully reached populations in need of sexual and reproductive health services and suggest that these facilities can help play an important role in reducing disparities even after full implementation of the Affordable Care Act. However, more research is needed to fully quantify the need and value of Title X-funded family planning clinics and its relation to the changing health care environment in the US.

Prevalence of human papillomavirus in oropharyngeal squamous cell carcinoma in the United States across time

Human papillomaviruses (HPVs) are involved in approximately 5% of all human cancer. Although initially recognized for causing nearly all cases of cervical carcinoma, much data has now emerged implicating HPVs as a causal factor in other anogenital cancers as well as a subset of head and neck squamous cell carcinomas (HNSCCs), most commonly oropharyngeal cancers. Numerous clinical trials have demonstrated that patients with HPV+ oropharyngeal squamous cell carcinoma (OPSCC) have improved survival compared to patients with HPV– cancers. Furthermore, epidemiological evidence shows the incidence of OPSCC has been steadily rising over time in the United States. It has been proposed that an increase in HPV-related OPSCCs is the driving force behind the increasing rate of OPSCC. Although some studies have revealed an increase in HPV+ head and neck malignancies over time in specific regions of the United States, there has not been a comprehensive study validating this trend across the entire country. Therefore, we undertook this meta-analysis to assess all literature through August 2013 that reported on the prevalence of HPV in OPSCC for patient populations within the United States. The results show an increase in the prevalence of HPV+ OPSCC from 20.9% in the pre-1990 time period to 51.4% in 1990–1999 and finally to 65.4% for 2000–present. In this manner, our study provides further evidence to support the hypothesis that HPV-associated OPSCCs are driving the increasing incidence of OPSCC over time in the United States.

Factors associated With Medicaid providers' recommendation of the HPV vaccine to low-income adolescent girls

PURPOSE

Human papillomavirus (HPV) vaccination in the United States remains a public health challenge with vaccine rates of 50%. Although health care providers can facilitate HPV vaccination, several factors may impede their ability to universally recommend the vaccine. To maximize the potential of HPV vaccines, it is important to understand challenges providers face in the clinical environment. The study sought to identify factors associated with recommendation of the HPV vaccine for low-income adolescents in the early (9-10), target (11-12), early adolescent catch-up (13-14), and late adolescent catch-up (15-17) vaccination groups.

METHODS

Surveys were mailed between October 2009 and April 2010 to a random sample of Florida-based physicians serving Medicaid-enrolled adolescents. Data were analyzed in 2013.

RESULTS

Among early adolescents, discomfort discussing sexually transmitted infections (STIs) with teens (odds ratio [OR] = 1.75), difficulty ensuring vaccine completion (OR = .73), and discomfort discussing STIs with parents (OR = .44) were associated with recommendation. For target adolescents, discomfort discussing STIs with teens (OR = 2.45), time constraints (OR = .70), vaccine efficacy concerns (OR = .65), discomfort discussing STIs with parents (OR = .33), obstetrics/gynecology (OR = .25) and family medicine (OR = .24) specialty, and non-Hispanic black patient (OR = .15) were associated with recommendation. In early catch-up adolescents, concerns that teens will practice riskier behaviors (OR = .57), discomfort discussing STIs with parents (OR = .47), and family medicine specialty (OR = .20) were associated with recommendation. For late catch-up adolescents, family medicine specialty (OR = .13) was associated with recommendation.

CONCLUSIONS

Modifiable factors that impede or influence provider recommendations of HPV vaccines can be addressed through intervention. Overall, findings suggest that efforts should focus on sexuality communication and family medicine specialty.

Evaluation of the acceptability and feasibility of a computer-tailored intervention to increase human papillomavirus vaccination among young adult women

OBJECTIVE

To examine acceptability and feasibility of a Transtheoretical Model (TTM)-based computer-tailored intervention (CTI) for increasing human papillomavirus (HPV) vaccination in college-aged women.

PARTICIPANTS

Two hundred forty-three women aged 18-26 were recruited between February and May of 2011.

METHODS

Participants completed the intervention and a 14-item evaluation of intervention content and delivery.

RESULTS

Most participants had heard of HPV (91%), but the majority (57%) of participants were in Precontemplation for getting vaccinated. Eighty-nine percent of participants rated the CTI positively across all acceptability items, and 91% endorsed intention to get vaccinated after intervention. Although average ratings in each demographic subgroup were positive, Hispanic women and participants in more advanced stages of change rated the program more favorably than non-Hispanic and earlier-stage participants. Additionally, HPV knowledge was higher among white/non-Hispanic participants.

CONCLUSIONS

Initial acceptability and feasibility data for this intervention are promising. Its computer-based, individually tailored format is state of the art and ideal for inexpensive dissemination.

MSMB gene variant alters the association between prostate cancer and number of sexual partners

BACKGROUND

Recently, a genetic variant (rs10993994) in the MSMB gene associated with prostate cancer (PCa) risk was shown to correlate with reduced prostate secretory protein of 94 amino acids (PSP94) levels. Although the biological activity of PSP94 is unclear, one of its hypothesized functions is to protect prostatic cells from pathogens. Number of sexual partners and a history of sexually transmitted infections (STIs) have been positively associated with PCa risk, and these associations may be related to pathogen-induced chronic prostatic inflammation. Based on these observations, we investigated whether MSMB genotype modifies the PCa-sexual history association.

METHODS

We estimated odds ratios (ORs) and 95% confidence intervals (CIs) for the association between number of sexual partners and PCa by fitting logistic regression models, stratified by MSMB genotype, and adjusted for age, family history of PCa, and PCa screening history among 1,239 incident cases and 1,232 controls.

RESULTS

Compared with 1-4 female sexual partners, men with ≥ 15 such partners who carried the variant T allele of rs10993994 were at increased risk for PCa (OR = 1.32; 95% CI, 1.03-1.71); no association was observed in men with the CC genotype (OR = 1.03; 95% CI, 0.73-1.46; P = 0.05 for interaction). Similar estimates were observed for total sexual partners (any T allele OR = 1.37; 95% CI, 1.07-1.77; CC genotype OR = 1.11; 95% CI, 0.79-1.55; P = 0.06 for interaction).

CONCLUSIONS

The rs10993994 genotype in the MSMB gene modifies the association between number of sexual partners and PCa risk. These findings support a hypothesized biological mechanism whereby prostatic infection/inflammation may enhance risk of PCa.

Cost-effectiveness analysis of the bivalent and quadrivalent human papillomavirus vaccines from a societal perspective in Colombia

Objective

To compare costs and effectiveness of three strategies used against cervical cancer (CC) and genital warts: (i) Screening for CC; (ii) Bivalent Human Papillomavirus (HPV) 16/18 vaccine added to screening; (iii) Quadrivalent HPV 6/11/16/18 vaccine added to screening.

Methods

A Markov model was designed in order to simulate the natural history of the disease from 12 years of age (vaccination) until death. Transition probabilities were selected or adjusted to match the HPV infection profile in Colombia. A systematic review was undertaken in order to derive efficacy values for the two vaccines as well as for the operational characteristics of the cytology test. The societal perspective was used. Effectiveness was measured in number of averted Disability Adjusted Life Years (DALYS).

Results

At commercial prices reported for 2010 the two vaccines were shown to be non-cost-effective alternatives when compared with the existing screening strategy. Sensitivity analyses showed that results are affected by the cost of vaccines and their efficacy values, making it difficult to determine with certainty which of the two vaccines has the best cost-effectiveness profile. To be ‘cost-effective’ vaccines should cost between 141 and 147 USD (Unite States Dollars) per vaccinated girl at the most. But at lower prices such as those recommended by WHO or the price of other vaccines in Colombia, HPV vaccination could be considered very cost-effective.

Conclusions

HPV vaccination could be a convenient alternative for the prevention of CC in Colombia. However, the price of the vaccine should be lower for this vaccination strategy to be cost-effective. It is also important to take into consideration the willingness to pay, budgetary impact, and program implications, in order to determine the relevance of a vaccination program in this country, as well as which vaccine should be selected for use in the program.

Clinical progression of high-grade cervical intraepithelial neoplasia: estimating the time to preclinical cervical cancer from doubly censored national registry data

Little is known about the time span of progression from high-grade cervical intraepithelial neoplasia (CIN2/3) to invasive cervical cancer. Estimation of this duration from longitudinal studies is not permitted, as CIN2/3 should be treated when detected. Cross-sectional data on the age-specific incidence of detected CIN2/3 and cervical cancer cases are readily available in national registries, but these data are difficult to interpret because neither the moment of lesion development nor the onset of invasive cancer is observed. We developed a statistical model for estimating the duration of time between CIN2/3 and preclinical cancer using Dutch national registries for the years 2000-2005. Human papillomavirus (HPV) genotype data were used to separate CIN2/3 and cancer incidences to obtain estimates for HPV-16-positive and HPV-16-negative lesions. The median time from CIN2/3 to cancer was estimated to be 23.5 years (95% confidence interval: 20.8, 26.6), and 1.6% of the lesions progressed to cancer within 10 years. The median duration for HPV-16-positive lesions was similar, but 2.4% of the HPV-16-positive lesions progressed to cancer within 10 years, as compared with 0.6% for HPV-16-negative lesions. Estimated durations of time to cancer are essential for reassessment of the optimal screening interval in light of vaccination and novel screening tests.

Risk factors for non-initiation of the human papillomavirus vaccine among adolescent survivors of childhood cancer

Effective vaccination is now available to prevent human papillomavirus (HPV), the most common sexually transmitted infection and cause of cervical cancer. This study aimed to estimate the prevalence of HPV vaccination among childhood cancer survivors and identify factors associated with HPV vaccine initiation and completion. Mothers of daughters of ages 9 to 17 years with/without a history of childhood cancer (n = 235, Mage = 13.2 years, SD = 2.69; n = 70, Mage = 13.3 years, SD = 2.47, respectively) completed surveys querying HPV vaccination initiation and completion along with sociodemographic, medical, HPV knowledge and communication, and health belief factors, which may relate to vaccination outcomes. Multivariate logistic regression was used to identify factors that associate with HPV vaccination initiation and completion. Among cancer survivors, 32.6% initiated and 17.9% completed the three-dose vaccine series, whereas 34.3% and 20.0% of controls initiated and completed, respectively. Univariate analyses indicated no differences between cancer/no cancer groups on considered risk factors. Among all participants, multivariate logistic regression analyses found vaccine initiation associated with older age of daughter and physician recommendation, whereas increased perceived barriers associated with a decreased likelihood of initiation (all P < 0.05). Among those having initiated, risk factors for noncompletion included being non-White, increased perceived severity of HPV, and increased perceived barriers to vaccination (all P < 0.05). A minority of adolescents surviving childhood cancer has completed vaccination despite their increased risk for HPV-related complication. These results inform the prioritization of strategies to be included in vaccine promotion efforts.

The four steps in the prevention of human papillomavirus-associated neoplasia: considerations for preventive measures, screening, disease impact, and potential overtreatments in HPV-related pathology

There is no cure currently available for HPV infections, although ablative and excisional treatments of some dysplasias often result in a clinical and virological cure. Effective control measures of HPV-associated cancers rely on the prevention at four different levels. Apart from sexual abstinence, primary prevention is realized through vaccines targeting the most frequent HPV types: negative attitudes towards HPV vaccination and high costs are the main obstacles. The aim of secondary prevention is to detect precancerous changes before they develop into invasive cancer, while tertiary prevention involves actual treatment of high-grade lesions: in many countries routine screening with cytology is being challenged with HPV DNA testing. Quaternary prevention comprehends those actions adopted to mitigate or avoid unnecessary or excessive medical interventions, and may well be addressed in avoiding treatments for low-grade intraepithelial neoplasia. Though some gynecologists commonly recommend treatment for low-grade disease and women tend to prefer active management if not properly informed, harms arising from unnecessary treatments, increased costs, work overload for second-level health services, and induced psychosocial distress are causing on-going problems. Prevention efforts of genital HPV-associated cancers should concentrate in: (1) enhancing primary prevention through vaccination of all eligible subjects, (2) achieving high levels of adherence to routine screening programs, (3) treating precancerous lesions, and (4) monitoring current guidelines recommendations to avoid overtreatments. Novel research projects should be designed to study the delicate mechanisms of immune response to HPV.

Sexually transmitted infections among US women and men: prevalence and incidence estimates, 2008

BACKGROUND

Most sexually active people will be infected with a sexually transmitted infection (STI) at some point in their lives. The number of STIs in the United States was previously estimated in 2000. We updated previous estimates to reflect the number of STIs for calendar year 2008.

METHODS

We reviewed available data and literature and conservatively estimated incident and prevalent infections nationally for 8 common STIs: chlamydia, gonorrhea, syphilis, herpes, human papillomavirus, hepatitis B, HIV, and trichomoniasis. Where available, data from nationally representative surveys such as the National Health and Nutrition Examination Survey were used to provide national estimates of STI prevalence or incidence. The strength of each estimate was rated good, fair, or poor, according to the quality of the evidence.

RESULTS

In 2008, there were an estimated 110 million prevalent STIs among women and men in the United States. Of these, more than 20% of infections (22.1 million) were among women and men aged 15 to 24 years. Approximately 19.7 million incident infections occurred in the United States in 2008; nearly 50% (9.8 million) were acquired by young women and men aged 15 to 24 years. Human papillomavirus infections, many of which are asymptomatic and do not cause disease, accounted for most of both prevalent and incident infections.

CONCLUSIONS

Sexually transmitted infections are common in the United States, with a disproportionate burden among young adolescents and adults. Public health efforts to address STIs should focus on prevention among at-risk populations to reduce the number and impact of STIs.

Quantifying the impact of dissimilar HPV vaccination uptake among Manitoban school girls by ethnicity using a transmission dynamic model

BACKGROUND

Gardasil, a human papillomavirus (HPV) vaccine, began among grade 6 girls in Manitoba, Canada in 2008. In Manitoba, there is evidence that First Nations, Métis, and Inuit women (FNMI) have higher HPV prevalence, lower invasive cervical cancer (ICC) screening, and higher ICC incidence than all other Manitoban (AOM) women. We developed a mathematical model to assess the plausible impact of unequal vaccination coverage among school girls on future cervical cancer incidence.

METHODS

We fit model estimated HPV prevalence and ICC incidence to corresponding empirical estimates. We used the fitted model to evaluate the impact of varying levels of vaccination uptake by FNMI status on future ICC incidence, assuming cervical screening uptake among FNMI and AOM women remained unchanged.

RESULTS

Depending on vaccination coverage, estimated ICC incidence by 2059 ranged from 15% to 68% lower than if there were no vaccination. The level of cross-ethnic sexual mixing influenced the impact that vaccination rates among FNMI has on ICC incidence among AOM, and vice versa. The same level of AOM vaccination could result in ICC incidence that differs by up to 10%, depending on the level of FNMI vaccination. Similarly, the same level of FNMI vaccination could result in ICC incidence that differs by almost 40%, depending on the level of AOM vaccination.

CONCLUSIONS

If we are unable to equalize vaccination uptake among all school girls, policy makers should prepare for higher levels of cervical cancer than would occur under equal vaccination uptake.

Cost-effectiveness of human papillomavirus vaccination in low and middle income countries: a systematic review

The World Health Organization recommends establishing that human papillomavirus vaccination is cost-effective before vaccine introduction. We searched Pubmed, Embase and the Cochrane Library to 1 April 2012 for economic evaluations of human papillomavirus vaccination in low and middle income countries. We found 25 articles, but almost all low income countries and many middle income countries lacked country-specific studies. Methods, assumptions and consequently results varied widely, even for studies conducted for the same country. Despite the heterogeneity, most studies conclude that vaccination is likely to be cost-effective and possibly even cost saving, particularly in settings without organized cervical screening programmes. However, study uncertainty could be reduced by clarity about vaccine prices and vaccine delivery costs. The review supports extending vaccination to low income settings where vaccine prices are competitive, donor funding is available, cervical cancer burden is high and screening options are limited.

Human papillomavirus vaccination: current indications and future directions

Human papillomavirus (HPV) is one of the most common sexually transmitted infections affecting both men and women worldwide. The development of the prophylactic HPV vaccines is a significant pharmaceutical innovation with potential to reduce HPV-related morbidity. However, barriers to the universal use and acceptability of the HPV vaccines continue to exist in both economically privileged and disadvantaged countries. It may be decades before the impact of preventive vaccines on HPV-related diseases caused by the considerable burden of HPV infections will be seen. Collaborative efforts must continue to promote vaccine implementation.

Screening for cervical cancer: a modeling study for the US Preventive Services Task Force

OBJECTIVE

This study addresses the following 3 questions posed by the US Preventive Services Task Force: (1) at what age should screening for cervical cancer begin; (2) at what age should screening for cervical cancer end; and (3) how do the benefits and potential harms of screening strategies that use human papillomavirus DNA testing in conjunction with cytology (cotesting) compare with those strategies that use cytology only?

MATERIALS AND METHODS

A Markov model was updated and used to quantify clinical outcomes (i.e., colposcopies, cancers, and life expectancy) associated with different screening strategies.

RESULTS

Screening in the teenaged years is associated with a high number of colposcopies (harms), small differences in cancers detected and, as a result, small gains in life expectancy (benefits). Screening women beginning in the early 20s provides a reasonable balance of the harms and benefits of screening. Among women who have been screened according to the current recommendations for cervical cancer (beginning at age 21 years and conducted every 3 years with cytology), screening beyond 65 years is associated with small additional gains in life expectancy but large increases in colposcopies. For cotesting, a strategy of cytology only conducted every 3 years, followed by cotesting conducted every 5 years (for women ≥30 years), is associated with fewer colposcopies and greater gains in life expectancy compared with screening with cytology only conducted every 3 years.

CONCLUSIONS

The results of this modeling study support current US Preventive Services Task Force recommendations for cervical cancer screening.

Adjunctive colposcopy technologies for examination of the uterine cervix--DySIS, LuViva Advanced Cervical Scan and Niris Imaging System: a systematic review and economic evaluation

BACKGROUND

Women in England (aged 25-64 years) are invited for cervical screening every 3-5 years to assess for cervical intraepithelial neoplasia (CIN) or cancer. CIN is a term describing abnormal changes in the cells of the cervix, ranging from CIN1 to CIN3, which is precancerous. Colposcopy is used to visualise the cervix. Three adjunctive colposcopy technologies for examination of the cervix have been included in this assessment: Dynamic Spectral Imaging System (DySIS), the LuViva Advanced Cervical Scan and the Niris Imaging System.

OBJECTIVE

To determine the clinical effectiveness and cost-effectiveness of adjunctive colposcopy technologies for examination of the uterine cervix for patients referred for colposcopy through the NHS Cervical Screening Programme.

DATA SOURCES

Sixteen electronic databases [Allied and Complementary Medicine Database (AMED), BIOSIS Previews, Cochrane Database of Systematic Reviews (CDSR), Cochrane Central Register of Controlled Trials (CENTRAL), Cumulative Index to Nursing and Allied Health Literature (CINAHL), Database of Abstracts of Reviews of Effects (DARE), EMBASE, Health Management Information Consortium (HMIC), Health Technology Assessment (HTA) database; Inspec, Inside Conferences, MEDLINE, NHS Economic Evaluation Database (NHS EED), PASCAL, Science Citation Index Expanded (SCIE) and Science Citation Index (SCI) - Conference Proceedings], and two clinical trial registries [ClinicalTrials.gov and Current Controlled Trials (CCT)] were searched to September-October 2011.

REVIEW METHODS

Studies comparing DySIS, LuViva or Niris with conventional colposcopy were sought; a narrative synthesis was undertaken. A decision-analytic model was developed, which measured outcomes in terms of quality-adjusted life-years (QALYs) and costs were evaluated from the perspective of the NHS and Personal Social Services with a time horizon of 50 years.

RESULTS

Six studies were included: two studies of DySIS, one study of LuViva and three studies of Niris. The DySIS studies were well reported and had a low risk of bias; they found higher sensitivity with DySIS (both the DySISmap alone and in combination with colposcopy) than colposcopy alone for identifying CIN2+ disease, although specificity was lower with DySIS. The studies of LuViva and Niris were poorly reported and had limitations, which indicated that their results were subject to a high risk of bias; the results of these studies cannot be considered reliable. The base-case cost-effectiveness analysis suggests that both DySIS treatment options are less costly and more effective than colposcopy alone in the overall weighted population; these results were robust to the ranges tested in the sensitivity analysis. DySISmap alone was more costly and more effective in several of the referral groups but the incremental cost-effectiveness ratio (ICER) was never higher than £1687 per QALY. DySIS plus colposcopy was less costly and more effective in all reasons for referral. Only indicative analyses were carried out on Niris and LuViva and no conclusions could be made on their cost-effectiveness.

LIMITATIONS

The assessment is limited by the available evidence on the new technologies, natural history of the disease area and current treatment patterns.

CONCLUSIONS

DySIS, particularly in combination with colposcopy, has higher sensitivity than colposcopy alone. There is no reliable evidence on the clinical effectiveness of LuViva and Niris. DySIS plus colposcopy appears to be less costly and more effective than both the DySISmap alone and colposcopy alone; these results were robust to the sensitivity analyses undertaken. Given the lack of reliable evidence on LuViva and Niris, no conclusions on their potential cost-effectiveness can be drawn. There is some uncertainty about how generalisable these findings will be to the population of women referred for colposcopy in the future, owing to the introduction of the human papillomavirus (HPV) triage test and uptake of the HPV vaccine.

Validation of decisional balance and self-efficacy measures for HPV vaccination in college women

PURPOSE

Women younger than 25 years are at greatest risk for human papillomavirus (HPV) infection, including high-risk strains associated with 70% of cervical cancers. Effective model-based measures that can lead to intervention development to increase HPV vaccination rates are necessary. This study validated Transtheoretical Model measures of Decisional Balance and Self-Efficacy for seeking the HPV vaccine in a sample of female college students.

DESIGN

Cross-sectional measurement development. Setting. Online survey of undergraduate college students.

SUBJECTS

A total of 340 female students ages 18 to 26 years.

MEASURES

Stage of Change, Decisional Balance, and Self-Efficacy.

ANALYSIS

The sample was randomly split into halves for exploratory principal components analyses (PCAs), followed by confirmatory factor analyses (CFAs) to test measurement models. Multivariate analyses examined relationships between constructs.

RESULTS

For Decisional Balance, PCA indicated two 4-item factors (Pros -α = .90; and Cons -α = .66). CFA supported a two-factor correlated model, χ(2)(19) = 39.33; p < .01; comparative fit index (CFI) = .97; and average absolute standardized residual statistic (AASR) = .03; with Pros α = .90 and Cons α = .67. For Self-Efficacy, PCA indicated one 6-item factor (α = .84). CFA supported this structure, χ(2)(9) = 50.87; p < .05; CFI = .94; AASR = .03; and α = .90. Multivariate analyses indicated significant cross-stage differences on Pros, Cons, and Self-Efficacy in expected directions.

CONCLUSION

Findings support the internal and external validity of these measures and their use in Transtheoretical Model-tailored interventions. Stage-construct relationships suggest that reducing the Cons of vaccination may be more important for HPV than for behaviors with a true Maintenance stage.

Human papillomavirus in adolescents: lessons learned from decades of evaluation

Knowledge regarding the natural history of human papillomavirus (HPV) infection and its clinical sequelae in adolescents has increased significantly over the last decade; as a result, there have been world-wide recommendations for less aggressive Pap screening and management of cervical dysplasias in young women. It is important that adolescent health providers understand these issues, as knowledge of HPV and its sequelae in the Australian community is limited, despite the introduction of a national immunisation programme. Parents and young women have expressed a desire for further information to make informed choices. This paper reviews the natural history of HPV infection in adolescents and the evidence behind new conservative guidelines for cervical screening, plus prophylactic vaccination in young women.

Novel health economic evaluation of a vaccination strategy to prevent HPV-related diseases: the BEST study

BACKGROUND

The development of human papillomavirus (HPV)-related diseases is not understood perfectly and uncertainties associated with commonly utilized probabilistic models must be considered. The study assessed the cost-effectiveness of a quadrivalent-based multicohort HPV vaccination strategy within a Bayesian framework.

METHODS

A full Bayesian multicohort Markov model was used, in which all unknown quantities were associated with suitable probability distributions reflecting the state of currently available knowledge. These distributions were informed by observed data or expert opinion. The model cycle lasted 1 year, whereas the follow-up time horizon was 90 years. Precancerous cervical lesions, cervical cancers, and anogenital warts were considered as outcomes.

RESULTS

The base case scenario (2 cohorts of girls aged 12 and 15 y) and other multicohort vaccination strategies (additional cohorts aged 18 and 25 y) were cost-effective, with a discounted cost per quality-adjusted life-year gained that corresponded to €12,013, €13,232, and €15,890 for vaccination programs based on 2, 3, and 4 cohorts, respectively. With multicohort vaccination strategies, the reduction in the number of HPV-related events occurred earlier (range, 3.8-6.4 y) when compared with a single cohort. The analysis of the expected value of information showed that the results of the model were subject to limited uncertainty (cost per patient = €12.6).

CONCLUSIONS

This methodological approach is designed to incorporate the uncertainty associated with HPV vaccination. Modeling the cost-effectiveness of a multicohort vaccination program with Bayesian statistics confirmed the value for money of quadrivalent-based HPV vaccination. The expected value of information gave the most appropriate and feasible representation of the true value of this program.

STI screening and treatment in pregnancy

Nurse practitioners provide care for pregnant women with sexually transmitted infections. This article discusses the latest guidelines for treatment of sexually transmitted infections in pregnant women and provides recommendations for screening, treatment, prophylaxis, and follow-up.

Inference of type-specific HPV transmissibility, progression and clearance rates: a mathematical modelling approach

Quantifying rates governing the clearance of Human Papillomavirus (HPV) and its progression to clinical disease, together with viral transmissibility and the duration of naturally-acquired immunity, is essential in estimating the impact of vaccination programmes and screening or testing regimes. However, the complex natural history of HPV makes this difficult. We infer the viral transmissibility, rate of waning natural immunity and rates of progression and clearance of infection of 13 high-risk and 2 non-oncogenic HPV types, making use of a number of rich datasets from Sweden. Estimates of viral transmissibility, clearance of initial infection and waning immunity were derived in a Bayesian framework by fitting a susceptible-infectious-recovered-susceptible (SIRS) transmission model to age- and type-specific HPV prevalence data from both a cross-sectional study and a randomised controlled trial (RCT) of primary HPV screening. The models fitted well, but over-estimated the prevalence of four high-risk types with respect to the data. Three of these types (HPV-33, -35 and -58) are among the most closely related phylogenetically to the most prevalent HPV-16. The fourth (HPV-45) is the most closely related to HPV-18; the second most prevalent type. We suggest that this may be an indicator of cross-immunity. Rates of progression and clearance of clinical lesions were additionally estimated from longitudinal data gathered as part of the same RCT. Our estimates of progression and clearance rates are consistent with the findings of survival analysis studies and we extend the literature by estimating progression and clearance rates for non-16 and non-18 high-risk types. We anticipate that such type-specific estimates will be useful in the parameterisation of further models and in developing our understanding of HPV natural history.

A modified Latent Class Model assessment of human papillomavirus-based screening tests for cervical lesions in women with atypical glandular cells: a Gynecologic Oncology Group study

PURPOSE

In the absence of gold standard diagnoses, we estimate age-specific false-positive and false-negative prediction rates of HPV-, cytology-, and histology-based tests for significant cervical lesions (SCL) in US women with AGC-NOS Pap smear diagnoses.

METHODS

Modified Latent Class Model (LCM) analyses, with prevalence of SCL modeled as a function of age, were applied to GOG-0171 study data (n = 122). The accuracies of several HPV-based tests, including Hybrid Capture II high-risk HPV (HC2 H-HPV); carbonic anhydrase IX (CA-IX); and invasive histological diagnosis, were compared. 1-PPV and 1-NPV were written as functions of sensitivity, specificity, and prevalence to obtain age-specific false-positive and false-negative rates.

RESULTS

The histology-based test was nearly perfect (sensitivity = 1.00, CI = 0.98-1.00; specificity = 0.99, CI = 0.96-1.00). Otherwise, HC2 H-HPV performed best (sensitivity = 1.00, CI = 1.00-1.00; specificity = 0.87, CI = 0.79-0.94). The false-positive detection rates (1-PPV) for HC2 H-HPV were high (>17 %) at each age, while those of the histological diagnoses were low (<5 % at ages ≤60 and <17 % overall ages). False-negative prediction rates (1-NPV) for HC2 H-HPV were <0.11 % at each age and were uniformly lower than those of other tests, including the histology-based test (<0.25 %). CA-IX together with HC2 H-HPV did not improve performance.

CONCLUSIONS

Women with negative HC2 H-HPV can safely forego invasive treatment (i.e., cone or LEEP biopsy, hysterectomy) in favor of observational follow-up. Additional biomarkers must be found for use in combination with HC2 H-HPV to reduce false-positive rates. This novel application of a modified LCM exemplifies methods for potential use in future cancer screening studies when gold standard diagnoses are not available.

Ethnic differences in predictors of HPV vaccination: comparisons of predictors for Latina and non-Latina White women

The purpose of this study was to examine how social and behavioral factors such as age of first intercourse, mother-daughter communication, and perceived norms are associated with human papillomavirus (HPV) vaccination behaviors, and whether ethnicity moderates those associations (non-Latina White versus Latina participants). From June through December 2009, we surveyed a community sample of 309 White and Latina women, ages 15 to 30. We recruited participants from local health care clinics in Des Moines, Iowa. Vaccination status was not significantly different for Whites versus Latinas. The effects of age at first intercourse, mother-daughter communication about values related to sex, and descriptive norms of HPV vaccine uptake were all significantly moderated by ethnicity. The current findings reveal that sociocultural and behavioral factors that affect HPV vaccine uptake do not affect White and Latina women in the same fashion. In the future, public health campaigns about HPV and the HPV vaccine may be more effective if their messages are sensitive to these differences.

Cervical cancer in India and HPV vaccination

Cervical cancer, mainly caused by Human Papillomavirus infection, is the leading cancer in Indian women and the second most common cancer in women worldwide. Though there are several methods of prevention of cervical cancer, prevention by vaccination is emerging as the most effective option, with the availability of two vaccines. Several studies have been published examining the vaccine's efficacy, immunogenicity and safety. Questions and controversy remain regarding mandatory vaccination, need for booster doses and cost-effectiveness, particularly in the Indian context.