Literature Review on Dengue Fever and Vaccine

CHAPTER 2: LITERATURE REVIEW

2.1  Introduction

Prevalence of Dengue, knowledge and attitude regarding Dengue fever have been extensively being describe in many study from Asia and South America. However, when talking about Dengue vaccine and dengue vaccinations, there are only several study publish and most of it related to Sanofi Pasteur’s CYD-TDV vaccine known as Dengvaxia which will be further explain later. In these chapter, most of the articles are available online via UNIMAS CAIS library subscription and mainly extracted from EBSCO, PubMed Central and PLOS database. Open access database such as Google Scholar is used as well. Keyword applied upon searching the articles include ‘dengue vaccine’, attitude towards vaccinations’, ’vaccine expectation’, ‘willingness to pay’ and ‘associated factor’. Combinations for the different keyword were used as well for each database to increase sensitivity and specificity of the articles.

Upon review the focus of literature review related to the topic in South East Asia country such as Indonesia, Thailand and Vietnam, there are few promising articles from Indonesia and Vietnam-Thailand join study that much related to current topic. Despite much effort into finding relevant articles in more local setting, no related study was found in Malaysia except those related to Sanofi Pasteur’s CYD-TDV vaccine trial.

2.2 Literature Review

2.2.1 Dengue Virus and serotype

Dengue is an infection cause by Dengue Virus that been transmitted to human through mosquitoes such as Ae. Aegypti and Ae. Albopictus (Khetarpal & Khanna, 2016; WHO, 2009). Globally, there are 4 types of Dengue virus or serotypes which are DEN1, DEN2, DEN3 and DEN 4 which have multiple genotype and antigenic differences among them (Simmons, Farrar, Nguyen, & Wills, 2012). However, there is also a single case reported to be infected with DEN5 virus detected in a 37 years old farmer in Sarawak around 2007 (Mustafa, Rasotgi, Jain, & Gupta, 2015). However, since then, no more DEN5 case is reported.

Even though there are several types of Dengue virus, it clinical symptoms between each serotypes did not differ much. One infection with one serotypes may give a long life immunity towards that particular serotypes but not from the other (Simmons et al., 2012). However, there is a risk that the second Dengue fever cause by other type of Dengue virus may cause more critical outcome (WHO, 2009).

Malaysia has been continuously monitoring Dengue serotype since 2013 through sentinel clinics and hospitals. In 2013, DEN2 is the most prevalence Dengue serotype in Malaysia followed by DEN1, DEN3 and DEN4. To the end of 2015, there is a serotype shift whereby DEN1 become more prominent followed by DEN2, DEN3 and DEN4. DEN 3 detection has been increasing since early 2015 and become the most prominent Dengue serotype in early 2017 follow by DEN2, DEN1 and DEN4. Sarawak however still has DEN1 as the prominent Dengue serotypes circulated among its population follow by DEN2 (MOH Malaysia, 2017).

2.2.2 Current conventional Dengue control and prevention method

There are several strategies implemented by Ministry of Health Malaysia to control and prevent Dengue infections as recommended by WHO in its Global Strategy 2012-2020 (WHO, 2012, 2017). Malaysia currently rely on passive surveillance system to capture Dengue cases incidence (J Gubler, 2002) which required Dengue cases to be notify to the nearest District Health Department, Ministry of Health Malaysia within 24 hours. The Dengue control then would be carry out based on the notifications given. In certain area especially in urban setting, Dengue control responsibilities also share with Local Authorities or Municipal Council under Ministry of Housing and Local Government.

Control measure such as thermal fogging at the premises and area which reported dengue cases and with high amount of Aedes mosquito population, follow by Ultra Low Volume fogging in the surrounding area arguably the most common activities perform (Lokman Hakim S & MOH Malaysia, 2016; Raviwharmman Packierisamy et al., 2015; Sector of Vector Borne Disease Control, Ministry of Health Malaysia, 2014). Larvaciding which is insecticides applications at the potential Aedes breeding site will be carry out as well together with destruction of potential Aedes breeding site following entomology assessment especially in an outbreak area (Sector of Vector Borne Disease Control, Ministry of Health Malaysia, 2014). The method use in Malaysia is not much different from it neighbouring country (Ooi, Goh, & Gubler, 2006; Phuanukoonnon, Mueller, & Bryan, 2005) and the Latin American country (Alfonso-Sierra et al., 2016; Augusto et al., 2016). Even though these approaches have proven to control the Aedes population (Gratz, 1993), it alone are unable to break the chain of Dengue fever infection as evidence by recurrence Dengue outbreak in similar area and increasing Dengue cases (Lokman Hakim S & MOH Malaysia, 2016).

Thus, Dengue prevention also fall into the local communities’ responsibilities. It is important for the communities to engage in destruction of Aedes breeding site and to prevent being bite by the Aedes mosquitoes by using repellents. Communications for Behavioural Impact (COMBI) is one of the initiatives to increase awareness and to empower the communities in fighting Dengue. COMBI contains 2 simple yet important messages to the community which is to do destroyed of any potential Aedes breeding site at one home and to seek treatment for fever as soon as possible if reside in Dengue outbreak area. Nonetheless, the COMBI initiative in Malaysia is not going to the desired behavioural changes and is not sustainable in the communities (M. Azmawati, 2015; M. N. Azmawati, Aniza, & Ali, 2013; Suhaili et al., 2004).

Aedes especially Ae. Albopictus usually be found in the surrounding environment rather than in the house (WHO, 2017). Hence, environmental management and cleanliness are important to destroy any potential Aedes breeding site outside the house. Ministry of Health alone unable to tackle the issues thus integrated vector management with the help of other organizations such as Ministry of Human Resource, Ministry of Housing, Ministry of Educations and local governments are needed (Lokman Hakim S & MOH Malaysia, 2016). Activity such as regular communal cleaning also play an important role to increase community awareness and destroying Aedes potential breeding site (Sector of Vector Borne Disease Control, Ministry of Health Malaysia, 2014).

2.2.3 Knowledge, attitude and Practice on Dengue fever

One of the major aspects that is crucial in Dengue control is the knowledge of the population regarding Dengue and its vector, the Aedes mosquito. How much the population knows about the disease would result in how much they would react to it as explain in the Health Believe Model. The knowledge theoretically would change the population behaviour into disease prevention. However not all the population who reside in Dengue outbreak area possess good knowledge regarding Dengue fever and Aedes mosquitoes especially those observe in South Asia countries (Dhimal et al., 2014; Itrat et al., 2008; Syed et al., 2010). This would translate in poor prevention measure taken by the communities against Aedes control.

Despite the poor knowledge outcome in South Asia countries, a different situation occurs in South East Asia countries such as Indonesia, Malaysia, Thailand and Vietnam. All the studies on the knowledge about Dengue fever and Aedes mosquito in the region illustrate good level of knowledge, however the gap between a good knowledge and respondents attitude and practices towards Dengue is observes in certain parameters as good knowledge is not translated into good practice (Al-Dubai, Ganasegeran, Alwan, Alshagga, & Saif-Ali, 2013; Balsam Mahdi Nasir Al-Zurfi, 2015; Hadisoemarto & Castro, 2013; Harapan, Anwar, Bustaman, et al., 2016; Koenraadt et al., 2006; Nalongsack, Yoshida, Morita, Sosouphanh, & Sakamoto, 2009; Wan Rozita WM, 2006; Wong, Shakir, Atefi, & AbuBakar, 2015).

In a study done to assess the knowledge and practice among urban, semi urban and rural communities in Selangor and Kuala Lumpur discover that one third of the respondents believe that elimination of Aedes larvae from the search and destroy activities is a waste of time (Al-Dubai et al., 2013). This is an example that indicate having good knowledge does not mean the prevention method is practice accordingly. This may be due to the fact that the respondents don’t perceived Dengue infection as a threat for them.

By having good attitude towards Dengue or having personal experience with Dengue infection may contribute to better Dengue vaccine acceptance (Hadisoemarto & Castro, 2013). (Harapan, Anwar, Bustaman, et al., 2016) has conduct a study to examine the effect of knowledge, attitude and practice towards dengue vaccination and suggest that all play attitude regarding dengue is the strongest domain that correlate with attitude towards dengue vaccinations with r = 0.67. Other factors like the respondents’ knowledge and practice also been found significant (p < 0.001) towards their attitude to vaccination with lower correlation (0.20 and 0.25). Thus it shows that knowledge, attitude and practice play important role for future dengue vaccination programme. Current awareness campaign and programme deem to be relevant to prepare the population towards more advance Dengue control and prevention such as vaccination programme.

2.2.4 Socio-economic status and Dengue fever

Most of dengue cases and outbreak occur in low to middle income countries, thus understanding their social economic capacity is vital especially drawing conclusion in regarding for future Dengue vaccination programme. High socio-economic status in the community is among the factor that contribute to Dengue prevention in local setting (Wan Rozita WM, 2006). This statement is also evidence by several study done in South Asia countries that show strong correlation between high socio-economic status and Dengue prevention practices and attitude (Dhimal et al., 2014; Itrat et al., 2008; Syed et al., 2010).

While Wan Rozita WM, 2006 observe the relation between high socio-economic with Dengue prevention practice, the similar result was not share with other researcher. Hairi et al., 2003 among other speculate that there is no different in level of Dengue prevention practice with higher socio-economic status and statistically is insignificant (Al-Dubai et al., 2013; Balsam Mahdi Nasir Al-Zurfi, 2015; Hairi et al., 2003). This might be due to the fact Dengue is highly endemic in the country and the awareness campaigns and programme related to Dengue has able to increase population knowledge regarding the Dengue prevention practices Interestingly where most of the studies conclude either there is correlation between good household income with better prevention practice or no correlation at all, Wong et al., 2015 argue that the lower households income and unemployed in Malaysia carry out is the who significantly carry out more Dengue prevention practices compare to others.

In study done analyse the Dengue vaccine acceptance in Bandung and Aceh, Indonesia, it is concluded that high socio-economic status is one of the major factor that correlate to Dengue vaccine acceptance (Harapan, Fajar, Sasmono, & Kuch, 2017). The low socio-economic status was related to lower acceptance of vaccination programme not just for Dengue but other infectious diseases such as Human papillomavirus (Jeudin, Liveright, del Carmen, & Perkins, 2013) and cholera (Merten et al., 2013). Study in Aceh also demonstrate type of occupation (such as civil servant) and level of educations are the cofounding factors of socio-economic status (Harapan, Anwar, Setiawan, & Sasmono, 2016). Socio-economic status thus plays an important role towards good attitude and acceptance of Dengue vaccine among the population and lacking of socio-economic assessment for Dengue vaccination programme especially in Malaysia will contribute difficulties in programme implementation.

2.2.5 Dengue vaccine

Due to its complexity, a good Dengue vaccine should cover all 4 Dengue serotypes as partial protection among its serotype may expose the population more serious clinical outcome if contracted with Dengue fever.