The impact of vaccination on gender equity: conceptual framework and human papillomavirus (HPV) vaccine case study

Vaccines are one of the most effective public health innovations in the past century. Every year immunizations save between two and three million lives and avert billions of dollars in costs of illness [1]. Not only are most vaccines cost-effective [2], but childhood immunizations are estimated to have a return on investment of 16 to 44 times the costs in the current decade [3]. Beyond saving lives, improving health and enhancing economic growth, vaccines also deliver wider societal benefits [4]. For example, vaccination can impact children’s cognitive development [5‐7] and educational attainment [8‐10]. Moreover, vaccination has been found to improve equity by reducing income-related disparities and reducing poverty [11‐13]. Although the beneficial effects of vaccines on equity by socioeconomic status and geography are increasingly well-documented, little has been done to extend these analyses to examine the linkage between vaccination and gender equity.

Achieving gender equity and empowering all women and girls is one of the United Nations’ Sustainable Development Goals and a key foundation for a peaceful, prosperous, and sustainable world [14]. Gender inequity relates to health as gender-related power imbalances contribute to excess female mortality, gender-based violence, and limited health-seeking behaviors including lower access to reproductive healthcare [15, 16]. When women and girls receive healthcare, are educated, are not married as a child, and can earn and control income, economies expand and cycles of poverty are broken [17]. While one suggested approach has been to target these conditions directly with policy [17], we sought to examine the link in the other direction from health to development, i.e., whether vaccination in turn can contribute to gender equity.

The linkage between vaccines and gender equity is particularly relevant in the case of the human papillomavirus (HPV) vaccine. HPV vaccine studies demonstrate an almost 100% protection against the previously high-risk HPV strains that cause cervical cancer (types 16 and 18), and HPV vaccines have been shown to be cost-effective in most settings [18‐20]. While HPV causes disease in both females and males, globally almost 90% of the HPV vaccine-preventable disease burden falls on females [21]. In women, cervical cancer is the second leading cause of new cases of cancer and cancer death worldwide [22]. Hence we hypothesize that HPV vaccination among girls could help narrow socioeconomic gender disparities by reducing the cervical cancer burden that women experience and increasing the opportunities afforded by improved health.

In this paper, evidence from the published literature is used to develop a conceptual framework demonstrating the potential impact of vaccination on measures of gender equity. This framework is then applied to the HPV vaccine example in three countries with different economic and disease burden profiles to establish the impact of improved health on gender equity in a variety of development contexts. Our objective is to provide a proof of concept model as a starting point to inform future analyses that seek to estimate the health and economic impact of gender equity.

We developed a conceptual framework that links vaccination and gender equity utilizing existing literature. In our case study, we found that HPV vaccination could help narrow socioeconomic gender disparities by quantifying the main pathways by which HPV vaccination improves health, which enables improvement in gender equity indicators such as labor force participation and maternal mortality ratios. Specifically, we found that the years of employment gained among women with averted cervical cancer ranged from 165 to 920 years in Tanzania, 1404–9600 years in India, and 38–78 years in the United Kingdom for women aged 15 to 49 years. The averted maternal deaths among women with averted cervical cancer was 1.4 in Tanzania and 2.3 in India. These improvements likewise translate to improvements in gender equity. While these improvements are small when averaged over the entire population, the components measured – labor force participation and maternal mortality ratio – account for 50% of the index score.

While the magnitude of improvement we found is small due to the rarity of cervical cancer, we have likely underestimated the benefits. This is because our model did not include many other benefits of HPV vaccination such as indirect (herd) effects, social stigma associated with cervical and other HPV-related cancers, reductions in time-consuming and anxiety-inducing cervical screening and treatment rounds, as well as effects on non-cervical HPV-related disease such as vulvar, vaginal, anal and oropharyngeal cancers [21, 51]. We also only assumed vaccination coverage of girls, per the WHO recommendations for routine immunization [52], whereas many countries also vaccinate boys. However, even if countries were to vaccinate both girls and boys, we would still likely see a gender equity benefit due to the health benefits of HPV vaccination primarily accruing among girls [53]. Furthermore, we have only explored two of the many pathways between improved health and gender equity (via female labor participation and maternal mortality) because of the availability of existing models of these pathways and their inclusion in the GII. In particular, the pathway between improved health and gender equity via improvements in female educational attainment is relevant [5, 8, 9, 38, 44, 46, 54], but excluded in this analysis due to limited data and the late age of onset of cervical cancer. Additionally, given the late age of onset of HPV compared to other vaccine-preventable diseases, it may be possible that the impact of vaccination against childhood diseases could have a larger impact on gender equity. Despite these limitations, our work provides for the first time, to our knowledge, both a proof of concept and quantitative links between vaccination and gender equity.

In this analysis, we selected HPV vaccination as a case study for gender equity given that its health benefits are predominantly in women [53]. If we examined a vaccine that was more gender-neutral in the acquisition of health benefits such as measles or rotavirus, health improvements among both men and women would impact both labor force participation and fertility rates. According to Bloom, et al., male health improvements increase the fertility rate, which would likewise decrease the female labor force participation rate [27]. Therefore, if a health intervention such as vaccination improved the health of both sexes equally, the macroeconomic effects may be counteracting. However, given that an economy has transitioned to a regime of “declining fertility and increasing educational investments,” the dynamic equilibrium model developed by Bloom, et al., found that gender-neutral health improvements still improved overall economic growth via female labor force participation and declining fertility [27]. The paper further states that health improvements among both sexes also supports the transition from a high fertility regime to a low fertility regime. In the case of vaccination in LMICs, the net improvement of a gender-neutral vaccination might therefore lead to improvements in gender equity, although likely to a lesser extent than an HPV vaccination program. Hence, we can conclude that most immunization programs are likely to contribute to gender equity as long as they achieve equal uptake among males and females.

Equity is a key criterion for health technology assessments in many countries [55, 56] and by organizations such as the Bill & Melinda Gates Foundation [57]. Up to now, most of the literature around vaccines and equity has focused on socioeconomic [58‐60] and geographical [61‐63] dimensions of equity. Additionally, suggestions to address gender equity and female empowerment as part of the Sustainable Development Goals have focused on policies around dimensions of gender equity, rather than health [17]. Our work shows that vaccines may also help to narrow gender disparities by a conceptual framework that links improvements in health to dimensions of gender equity, and that the magnitude of such effects can be quantified. Furthermore, we have shown that those effects improve the same dimensions that have been identified as essential to gender equity, where gaps still remain [17, 64].

Given the importance of gender equity to development, this suggests that decision-making bodies such as national immunization technical advisory groups (NITAGs) and donors may wish to consider vaccine impact on gender equity as one of the decision-making criteria around new vaccine introductions. Future research should be conducted to examine these gender equity benefits beyond this case study of three countries from the lens of HPV vaccination.

This analysis presents a number of limitations. First, our conceptual framework and quantitative associations rely on the available published literature, which remains limited on this topic. Specifically, we rely heavily on Bloom, et al. [27], which reports on a dynamic general equilibrium model of economic development across countries, and may not be generalizable to the settings that we feature in this analysis. Additionally, as the percentages obtained from this model are applied across all ages equally, the results of our analysis would be affected if the age distribution of disease by country is heavily skewed towards younger or older women. In order to address this limitation, we conducted a sensitivity analysis on the impact of improvements in health on female labor force participation and fertility with lower and upper bounds of 0.5 and 2 times multipliers, which would encompass environments where the age distribution of disease trends toward older women, i.e., lower reductions in fertility and improvements in labor force participation, or younger women, i.e., greater reductions in fertility and improvements in labor force participation. Second, in order to preserve the decreased life expectancy at birth and the increased life expectancy for individuals who survive infancy in our calculations of healthy life expectancy, we applied a constant to life expectancy between birth and age 60, but did not apply the constant beyond age 60. While this approximates the trend of the life expectancy curve, this approach results in a discontinuity at age 60 that should be smooth, but is necessary to provide a reasonable estimate of healthy life expectancy between age 60 and 100. Third, we assumed that the relationship between health and equity is the same across countries, but it may vary, as it contains inherent cultural and infrastructural assumptions that are not country-invariant. Fully addressing the relationship between health and equity in each country would require econometric analysis at the country level. We were also unable to control for changes in female labor force participation due to events unrelated to vaccination. Fourth, the individual-level impact of reduced cervical cancer on female labor force participation and fertility are less certain compared to vaccines which cause sequelae from early childhood. We might still expect to see individual-level fertility effects with HPV vaccine due to health expectations, e.g., if women are less likely to expect to be ill and have fertility affected in later life due to cervical cancer, then they may be more inclined to invest in education, delay childbirth, or even reduce fertility. Additionally, a woman who has cervical cancer and recovers may well have her fertility negatively affected since many of the treatments for cervical cancer affect fertility [65]. In order to address this uncertainty, we have conducted a sensitivity analysis on the fertility effect. Finally, the model presented here does not represent a causal relationship between HPV vaccination and gender equity.

While our analysis focused on reductions in gender inequity from overall improvements to healthy life expectancy, Finlay and Lee (2018) have examined the causal linkages between improvements in reproductive health, specifically, and the economic empowerment dimensions of gender equity [66]. This analysis relied on empirical evidence to draw similar conclusions that reproductive health improvements can and do empower women through effects on education, labor force participation, and childbearing. However, our analysis takes these results a step further by providing a proof of concept model for how a public health intervention such as vaccination could have a quantifiable impact on gender equity. Finally, there remains uncertainty in improvements in health, labor force participation, and fertility rate, particularly as applied to these specific country contexts. However, we hope to have addressed part of this uncertainty by including ranges from sensitivity analyses.

Gender equity is one of the United Nations’ Sustainable Development Goals and a key dimension of inclusive economic growth. It has been associated with improvements in health outcomes for women and children, in addition to economic growth. This proof of concept model is a starting point to inform future health and economic analyses that might incorporate the impact of gender equity as an additional impact of vaccination in improving the health and well-being of the population. Reduced HPV incidence may lead to improved gender equity through improvements in female contributions to the labor market and economic productivity, improvements in female education, lower fertility, and reduced youth dependency.