Malaria has remained a public health hurdle for more than a century since its discovery [1]. In 2021, more than 247 million people were infected with malaria, and approximately 619,000 people were killed globally, with 95% of the burden recorded in Africa and mostly 65% in children under five years of age [2]. Tanzania is among eight (8) countries bearing more than 60% of the global malaria burden, and in 2022, an 8% prevalence of malaria in children under five years of age was recorded [3]. Since 2000, after the renewal of commitment to malaria control and elimination in endemic countries, primary malaria control strategies have been based on the use of effective antimalarial drugs and vector control using insecticide-treated bed nets (ITNs) and indoor residual sprays (IRSs) [2]. These control strategies effectively reduced the malaria burden by 68% [4] in Africa by 2015; however, malaria control success has been slightly reversed, with cases and deaths increasing [5]. The development of resistance in malaria parasites and vectors to the chemical products used in their control might be the reason for the current reversal of success in malaria control [6]. These challenges facing current interventions have necessitated global malarial control stakeholders to rethink additional control strategies to be integrated with existing strategies to accelerate the pursuit of eradicating this deadly disease.
Vaccines, among the most effective interventions for eradicating several deadly infectious diseases, are considered effective additional tools in the fight against malaria. There have been trials of approximately 17 malaria candidate vaccines, some in the preclinical stages and others in different phases of clinical trials [7]. The RTS, S/AS01 and R21/Matrix-M vaccines developed from the sporozoite protein known as circumsporozoites have shown substantial efficacy and safety [8, 9]. These vaccines have been recommended by the World Health Organization for use in underfive-year-old children in malaria-endemic areas [10, 11].
The R21/Matrix-M vaccine is in phase 3 of clinical trials and has shown 75% efficacy against clinical malaria for one year of follow-up. This efficacy aligns with the WHO's goal of being very effective in malaria control and elimination [12]. Due to the high efficacy of the R21/Matrix-M vaccine in underfives, two countries in Africa (Ghana and Nigeria) have approved it for use despite a phase 3 clinical trial [13]. On the other hand, four doses of RTS and the S/AS01 vaccine have gone through all phases of clinical trials and have shown approximately 40% efficacy in reducing clinical malaria and 30% efficacy in reducing severe malaria for 5 months to underfives [11, 13]. Additionally, 40% vaccine efficacy surpasses the efficacy of ITNs in malaria control. From 2019 to 2021, pilot roll-outs of this vaccine were conducted in three African countries: Ghana, Kenya and Malawi [13]. Moreover, in 2021, the WHO endorsed the RTS S vaccine for broader roll-out in areas with moderate to high malaria transmission [14].
After the endorsement of the RTS, the S vaccine, WHO, GAVI and UNICEF have allocated 18 million doses of RTS, S to twelve (12) countries in sub-Saharan Africa as the first wider roll-out of such a vaccine in mid-2023 [14]. This vaccine allocation, if effectively utilized, will lead to groundbreaking breakthroughs in malaria eradication for underfives living in endemic areas. However, there has been a growing tendency toward vaccine hesitancy, and if such a phenomenon is not addressed satisfactorily, the substantial benefit of the vaccine will not be realized [15]. During the outbreak of the COVID-19 pandemic, the tendency for vaccine hesitancy has increased immensely due to misinformation on COVID-19 vaccine efficacy and safety [16]. If that misconception continues, this increase in vaccine hesitancy during COVID-19 might also affect the acceptance of malaria vaccines. For instance, UNICEF reported that the percentage of immunized children in some countries decreased to 44% during the COVID-19 pandemic [13]. Therefore, it is crucial to investigate the magnitude of malaria vaccine acceptance and address all misconceptions existing in communities before vaccine rollout.
In the coming years, Tanzania is preparing to receive the malaria vaccine and integrate it into its Expanded Program on Immunization (EPI) [17]. Nonetheless, during the COVID-19 pandemic, Tanzania experienced the highest degree of COVID-19 vaccine hesitancy until late 2022 [18, 19]. Such vaccine hesitancy emanates from misinformation on vaccine efficacy and safety, and most misconceptions are amplified and spread through media, including social media. The areas affected mainly by vaccine hesitancy were large cities where misconceptions are easily shared with many people. This high hesitancy of the COVID-19 vaccine experienced in Tanzania might also affect the country's acceptance of the malaria vaccine. Therefore, it is vital to assess the acceptance of the coming malaria vaccine by children's caregivers and address the existing misconceptions before integrating it into the EPI program in the county. In that context, this study investigated the awareness and willingness of underfive caregivers in Dar es Salaam city.