Vaccination remains the most effective means of reducing the burden of infectious disease besides clean water and sanitation , and has been estimated to prevent between three to about six million vaccine-preventable deaths annually . It is one of the most clinically and cost-effective public health innovations for promoting child health because of its direct health benefits and positive externalities [3, 4]. Vaccination has mitigated major epidemics of life-threatening diseases, eradicated many, besides being the surest prophylaxis against morbidity and mortality from vaccine-preventable diseases, and a significant contributor to national disease elimination and eradication efforts [5, 6].
However, despite the tremendous progress and being one of the most successful public health interventions yet, basic vaccination coverage remains below the 90% and 80% target at national and sub-national levels [7, 8]. An estimated 5.3 million child death from the 679 million under five years old (Under-5) in 2018, out of which over 700,000 are from vaccine-preventable infectious diseases, and 99% of them lived in low-and-middle-income countries (LIMC) . In the Sub-Saharan Africa (SSA) region, basic vaccination coverage of diphtheria-tetanus-pertussis (DTP3) has stagnated at an average of 72% in the last decade, the lowest among World Health Organization (WHO) member regions, even lower than the global average of 86% [10, 11]. Before the Coronavirus (COVID-19) pandemic, about 20 million infants are either under or unvaccinated annually, most of whom are in Sub-Sahara Africa region, where deaths rate from vaccine-preventable-diseases (VPD) for children under-fives years old (Under-5) remains the highest in the world [12, 13].
In Kenya, basic childhood vaccination coverage was lower (82%) than the global average (86%) in 2020 [11, 14, 15]. The national DTP3 coverage has been inconsistent in the last decade as seen in Fig. 1 . At the county levels, similar scenarios are observed too. While it has increased from 63% in 2000 to 83% in 2019, in quarter one of 2019, 21 Counties (44%) had 80% of DTP3 coverage but this dropped to 16 counties (34%) in quarter 2 . There has been 68% stark differential in immunization coverage across the 47 counties in Kenya . In 2017, only 6 of the 47 counties (13%) had basic vaccination (DPT3) coverage of at least 90%, while only 9% (four counties) had MMR 1 coverage of at least 95% – the lowest coverage reported in the country since 2011 [18, 19].
Similar trend (vaccine hesitancy) can also be noticed for Human papillomavirus (HPV) vaccination as well. HPV infection is the common cause of cervical cancer [20–22], with more than half of sexually active population contracting it during their lifespan . While over 70% of all cervical cancer cases are attributed to HPV types 16 and 18, it is the second most prevalent type of cancer among women [20, 24]. In 2020, an estimated 604, 000 new cases and 342, 000 deaths occurred, and about 90% of these occurrences were in low-and-middle-income countries (LIMC), predominantly in Sub-Saharan Africa [21, 25]. In 2018, 20 countries (except Bolivia) with the highest global burden of cervical cancer are in SSA and Kenya ranked 20th [26, 27].
In Kenya, over 50% of women who got infected with HPV died in 2018, i.e., nine death per day, with 14.3 million more women at risk of having cervical cancer [20, 28]. HPV vaccination was introduced in October 2019 for girls aged 10 years old in Kenya, in line with recommendations of the WHO’s Strategic Advisory Group on Immunization (SAGE), that HPV vaccination should be administered to young girls between the ages of 9–14 years before the onset of sexual activity .
Studies in Kenya have shown that vaccine acceptance is influenced by several factors including scheduling, knowledge gaps about immunization, behavioral components, including myths and misconceptions about vaccination [29, 30]. In 2018, according to the WHO/UNICEF Joint Reporting Form, three reasons reported to be driving vaccine hesitancy in Kenya are fear of adverse events from immunization (AEFI), religious belief and mythical or conspiratorial theories and misconception about vaccination . However, these reasons are not grounded in empirical evidence, rather the opinions of field health officers. Similarly, empirical findings from a systematic review of 13 countries in the Sub-Saharan Africa (SSA) (including Kenya) shows that low demand for HPV vaccine uptake is associated with risk perception of HPV vaccine, concerns about its safety and effectiveness, inadequate knowledge, and awareness [31–33].
Therefore, the tremendous successes made over childhood immunization are still incomparable to the target, let alone the stagnant or reversal of some of these gains in the last decade owing to behavioral reasons and other vaccine-related controversies [34, 35]. The same applies to the newly introduced HPV vaccine. Kenya HPV vaccine uptake has been sub-optimal with only 33% of adolescent girls receiving the first dose in 2020 and half (16%) returning for the 2nd dose .
Studies have associated these vaccination stagnation, retrogression, or inconsistencies to vaccine hesitancy [6, 36–38]. Which was why WHO considered vaccine hesitancy as one of the top ten threat to global health . Vaccine hesitancy is defined as the delay in acceptance or refusal of vaccines despite availability of its services . As shown in Fig. 2, vaccine hesitancy is not an all-or-nothing situation, but is a continuum of a process from acceptance to complete refusal. Vaccine hesitancy is also perceived to be driven largely by factors such as confidence (level of trust in vaccine or provider), complacency (do not perceive a need for vaccine or do not value the vaccine), and convenience (access) . However, vaccine hesitancy is a complex and context-specific phenomenon, and depends on geography locations, time, types of vaccines or even groups .
There is dearth of empirical data on the context-specific factors that drives low vaccine demand or vaccine hesitancy for routine childhood immunization and vaccination of adolescent girls against HPV in Kenya. The availability of data is crucial for the development of evidence-based targeted interventions to reduce vaccine hesitancy and improve both childhood and adolescent vaccination uptake. Therefore, this study aimed to identify the context-specific factors that influence vaccine hesitancy from the point of view of both the immunization program stakeholders/community members (supply-side) and caregivers (demand-side).