Impact and Cost-Effectiveness of Human Papillomavirus Vaccination Campaigns

HPV vaccination coverage in three districts in Zimbabwe following national introduction of 0,12 month schedule among 10 to 14 year old girls

BACKGROUND

Zimbabwe has one of the highest incidence rates of cervical cancer in the world - 61.7 per 100,000 women. The government of Zimbabwe introduced bivalent HPV vaccine with a 0,12 month schedule to all 10-14 year old girls using a pulsed-campaign approach in May 2018 (dose 1) and May 2019 (dose 2).

METHODS

In August 2019, we conducted a population-based, two-stage cluster survey of households with girls who were eligible for the national HPV vaccination program to determine two-dose HPV vaccination coverage in three districts of Zimbabwe. All households with girls currently aged 11 to 15 years were line-listed through a census conducted in the pre-selected clusters from each district prior to survey administration. A simple random sample of eligible households was selected from these lists to estimate HPV vaccine coverage at sufficient power with a margin of error of +/- 5%. Criteria for district selection included estimated vaccine uptake (low, medium, high), rural/urban/peri-urban, geographic area, estimated number of girls not in school, and recent natural disasters or disease outbreaks. We oversampled households with girls aged 13 or 14 years at the time of dose 1.

RESULTS

On-time dose 1 uptake ranged from 88 to 94% and two-dose HPV vaccine coverage ranged from 75 to 86% across the three districts. Nearly all vaccinations occurred in schools, and less than 2% of girls did not attend school. There were challenges assessing ages of girls at schools prior to vaccination - 9% of girls vaccinated were less than 10 years old at time of dose 1.

DISCUSSION

Zimbabwe has demonstrated that high uptake and successful completion of 2-dose HPV vaccination can be achieved with an annual dosing schedule. Efforts going forward will need to focus on minimizing dropout between doses and routinizing annual vaccinations in schools for every subsequent new cohort of eligible girls in the country.

Inclusion of Additional Unintended Consequences in Economic Evaluation: A Systematic Review of Immunization and Tuberculosis Cost-Effectiveness Analyses

OBJECTIVE

Our objective was to review economic evaluations of immunization and tuberculosis to determine the extent to which additional unintended consequences were taken into account in the analysis and to describe the methodological approaches used to estimate these, where possible.

METHODS

We sourced the vaccine economic evaluations from a previous systematic review by Nymark et al. (2009-2015) and searched PubMed/MEDLINE and Embase from 2015 to 2019 using the same search strategy. For tuberculosis economic evaluations, we extracted studies from 2009 to 2019 that were published in a previous review by Siapka et al. We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidance. Studies were classified according to the categories and subcategories (e.g., herd immunity, non-specific effects, and labor productivity) defined in a framework identifying additional unintended consequences by Nymark and Vassall. Where possible, methods for estimating the additional unintended consequences categories and subcategories were described. We evaluated the reporting quality of included studies according to the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) extraction guideline.

RESULTS

We identified 177 vaccine cost-effectiveness analyses (CEAs) between 2009 and 2019 that met the inclusion criteria. Of these, 98 included unintended consequences. Of the total 98 CEAs, overall health consequence categories were included 73 times; biological categories: herd immunity 43 times; pathogen response: resistance 15 times; and cross-protection 15 times. For health consequences pertaining to the supply-side (health systems) categories, side effects were included five times. On the nonhealth demand side (intrahousehold), labor productivity was included 60 times. We identified 29 tuberculosis CEAs from 2009 to 2019 that met the inclusion criteria. Of these, six articles included labor productivity, four included indirect transmission effects, and one included resistance. Between 2009 and 2019, only 34% of tuberculosis CEAs included additional unintended consequences, compared with 55% of vaccine CEAs.

CONCLUSIONS

The inclusion of additional unintended consequences in economic evaluations of immunization and tuberculosis continues to be limited. Additional unintended consequences of economic benefits, such as those examined in this review and especially those that occur outside the health system, offer valuable information to analysts. Further work on appropriate ways to value these additional unintended consequences is still warranted.

Prospects for accelerated elimination of cervical cancer

Human Papillomavirus (HPV) infection is a necessary risk factor for cervical cancer. If HPV is no longer spread, no new cervical cancer precursors will occur. The timepoint for control of the HPV infection will therefore be a rate-limiting step for cervical cancer elimination. We used a validated dynamic HPV transmission model to estimate the age-specific HPV16 incidences and basic reproductive numbers (R0) with input data from Sweden. If R0 is below 1, a fade-out resulting in extinction is expected. Above age 35, we found an R0 of 0.4. Thus, when younger birth cohorts no longer transmit HPV to women >35 years of age, we predict that the HPV infection will no longer be sustained among the older women. Given adequate resources, campaigns to eliminate HPV that are designed based on the R0 measurements followed by screening to detect and treat pre-existing cervical cancer precursors could achieve accelerated cervical cancer elimination.

Rates of New Human Papillomavirus Detection and Loss of Detection in Middle-aged Women by Recent and Past Sexual Behavior

BACKGROUND

Understanding the source of newly detected human papillomavirus (HPV) in middle-aged women is important to inform preventive strategies, such as screening and HPV vaccination.

METHODS

We conducted a prospective cohort study in Baltimore, Maryland. Women aged 35-60 years underwent HPV testing and completed health and sexual behavior questionnaires every 6 months over a 2-year period. New detection/loss of detection rates were calculated and adjusted hazard ratios were used to identify risk factors for new detection.

RESULTS

The new and loss of detection analyses included 731 women, and 104 positive for high-risk HPV. The rate of new high-risk HPV detection was 5.0 per 1000 woman-months. Reporting a new sex partner was associated with higher detection rates (adjusted hazard ratio, 8.1; 95% confidence interval, 3.5-18.6), but accounted only for 19.4% of all new detections. Among monogamous and sexually abstinent women, new detection was higher in women reporting ≥5 lifetime sexual partners than in those reporting <5 (adjusted hazard ratio, 2.2; 95% confidence interval, 1.2-4.2).

CONCLUSION

Although women remain at risk of HPV acquisition from new sex partners as they age, our results suggest that most new detections in middle-aged women reflect recurrence of previously acquired HPV.