IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

FACTORS INFLUENCING PARENTS’ AWARENESS REGARDING CHILDHOOD IMMUNIZATION: FINDINGS OF CROSS-SECTIONAL STUDY IN NORTHEAST ISLAND DISTRICT,

Ooi P.L.1*, Heng Z.Y.2, Boon K.Y.3

1Department of Pharmacy, Health Clinic, Penang, Malaysia 2Department of Pharmacy, Jalan Health Clinic, Penang, Malaysia 3Department of Pharmacy, Bandar Baru Health Clinic, Penang, Malaysia

*Corresponding author: Ooi Poh Ling Klinik Kesihatan Sungai Dua, 11700 , Penang, Malaysia Email: [email protected]

https://doi.org/10.32827/ijphcs.6.3.130

ABSTRACT

Background: Vaccines play an important role in preventing serious infectious diseases in childhood. There are still existences of unvaccinated children with current immunization system in Malaysia. The aim of this study was to measure parents’ knowledge and practice regarding childhood immunization awareness and to evaluate their association with parental socio-demographic factors.

Materials and Methods: A cross sectional study was conducted among parents with child aged 6 years old and below who visited public health clinics in District of Northeast from October to December 2017. A total of 147 respondents were recruited by convenience sampling. Data was collected using a validated self-administered questionnaire.

Result: The mean of knowledge score and practice score among parents were 6.40 and 6.99 respectively. Significant association was noted for knowledge score with employment status (p < 0.001), education level (p <0.001) and family income (p = 0.001). Practice score was found significantly associated with education level (p = 0.006) and family income (p = 0.014). Parents’ knowledge score was positively associated with their practice score (Spearman's correlation coefficient 0.291, p < 0.001).

Conclusion: Immunization campaigns or education programs are required to improve parents’ knowledge and practice regarding childhood immunization awareness. Particular attention ought to be given to parents who were unemployed, with lower education level or family income.

Keywords: Childhood immunization, Parents, Awareness, Knowledge, Practice

Ooi P.L., Heng Z.Y. & Boon K.Y 130 https://doi.org/10.32827/ijphcs.6.3.130

IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

1.0 Introduction

Vaccines play an important role in preventing serious infectious diseases in childhood. Substantial achievements have been made with decline in morbidity of many vaccine- preventable diseases and their complications during the 20th century (Centers for Disease Control and Prevention, 1999). Immunization program was introduced in early 1950s in Malaysia and vaccines are provided free of charge in government health facilities.

Nevertheless, there is emergence of vaccine safety concern as the incidence of vaccine- preventable diseases declined (Smith, Woods, & Marshall, 2009). The dissemination of misinformation and conflicting vaccine safety information from internet and many other resources nowadays further adversely affect parents’ decisions to immunize their children (Zimmerman et al., 2005). Underused and undervalued of vaccination have been documented in a variety of settings (Awadh et al., 2014). Low immunization level could lead to resurgence of vaccine-preventable disease (Gangarosa et al., 1998). In Malaysia, there are still existences of unvaccinated children with current immunization system and outbreaks of vaccine- preventable diseases such as measles and diphtheria still occur sporadically (Ministry of Health Malaysia, 2017).

Parental knowledge and practice regarding childhood immunization awareness can affect the immunization uptake and timeliness for their children as they are main decision makers. Parental socio-demographic factors were shown to have influence on parents’ knowledge and practice regarding their children immunization (Al-lela et al., 2014). This study can provide valuable insight into parents’ knowledge and practice regarding their children immunization in Northeast Penang Island District and the associated parental socio-demographic factors.

2.0 Materials and Methods

A cross-sectional study was conducted from 1st October 2017 to 31th December 2017. Parents with child not more than 6 years old who were visiting public health clinics in District of Northeast Penang Island during the study period were included. Estimated sample size was calculated using one sample, continuous outcome formula (LaMorte, 2016). Convenience sampling method was used and 147 parents were participated in this study.

Validated questionnaire adopted from Awadh et al. (2014) (with author permission) which consisted of two parts was used in data collection. The first part contained parents’ socio- demographic data while the second part contained the knowledge and practice questionnaire regarding childhood immunization awareness. There were 10 questions on knowledge and 10 questions on practice. For scoring of questions, one point will be given for each correct answer and zero for wrong answers or no response.

Data were collected from eight public health clinics in the District of Northeast Penang Island (Jalan Perak, Bandar Baru Air Itam, Sungai Dua, Jalan Macalister, Air Itam, , and Lebuh Muntri). Cover letter describing the study objectives was explained and informed consent was obtained from the parents who agreed to participate in this study. Ooi P.L., Heng Z.Y. & Boon K.Y 131 https://doi.org/10.32827/ijphcs.6.3.130

IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

Subject confidentiality was ensured by utilizing identification code numbers on the questionnaire. This study was approved by the Medical Research Ethics Committee (MREC), Ministry of Health Malaysia.

Data were analyzed using Microsoft Excel 2007 and SPSS version 20 software. Descriptive statistical analysis was used to assess parents’ socio-demographic data, knowledge and practice scores. All data were tested for normality and were not normally distributed. Mann- Whitney test was used to evaluate the association between parents’ gender, marital status, place of living and employment status with their knowledge score as well as practice score. Kruskal-Wallis test was used to assess the association between parents’ age, number of preschool children, family size, race, religion, education level and family income with their knowledge score and practice score. Spearman correlation was used to find association relationship between parents’ knowledge score and practice score. P-value<0.05 was considered to be statistically significant.

3.0 Result

3.1 Parents’ Socio-demographic Characteristics

A total of 147 parents were participated in this study. The vast majority of the respondents were female (72.1%). Majority were aged between 30 and 40 years (55.8%). Most of the respondents were (69.4%). Majority of the respondents attained educational level of secondary school and above (52.4%) (Table 1).

Table 1 Socio-demographic characteristics of respondents Parameter Frequency (n=147) Percentage (%) Gender Male 41 27.9 Female 106 72.1 Age (years) <20 2 1.4 20-30 53 36.1 30-40 82 55.8 >40 10 6.8 Marital Status Married 146 99.3 Single 1 0.7 No. of preschool children 1-2 129 87.8 3-4 16 10.9 >4 2 1.4 Family size <4 79 53.7 4-6 60 40.8 >6 8 5.4

Ooi P.L., Heng Z.Y. & Boon K.Y 132 https://doi.org/10.32827/ijphcs.6.3.130

IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

Race Malay 102 69.4 Chinese 33 22.4 Indian 11 7.5 Others 1 0.7 Religion Islam 105 71.4 Buddhism 27 18.4 Hinduism 10 6.8 Others 5 3.4 Place of living Rural 16 10.9 Urban 131 89.1 Employment status Employed 114 77.6 Unemployed 33 22.4 Education level No formal education 1 0.7 Primary 1 0.7 Secondary 77 52.4 Tertiary education 68 46.3 Family income

3.2 Parents’ Knowledge and Practice regarding Childhood Immunization

The mean of the knowledge score and practice score were 6.40 and 6.99, respectively (Table 2).

Table 2 Knowledge score and practice score of respondents Score Mean Median Knowledge 6.40 7.00 Practice 6.99 8.00

Ooi P.L., Heng Z.Y. & Boon K.Y 133 https://doi.org/10.32827/ijphcs.6.3.130

IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

3.3 Knowledge and Practice regarding Childhood Immunization between Different Socio- demographic Characteristics of Parents

Table 3 Knowledge score across different socio-demographic parameters Parameter Knowledge Score Mean Median Za /χ2b value p-value Gender -0.188a 0.851a Male 6.49 7.00 Female 6.37 7.00 Age (years) 1.692b 0.639b <20 7.00 7.00 20-30 6.58 7.00 30-40 6.30 7.00 >40 6.10 5.50 Marital Status -0.346a 0.803a Married 6.40 7.00 Single 6.00 6.00 No. of preschool 0.098b 0.952b children 1-2 6.42 7.00 3-4 6.31 7.00 >4 6.00 6.00 Family size 0.537b 0.765b <4 6.42 7.00 4-6 6.31 6.50 >6 6.00 5.50 Race 6.642b 0.084b Malay 6.61 7.00 Chinese 6.21 6.00 Indian 5.36 5.00 Others 3.00 3.00 Religion 4.324b 0.229b Islam 6.54 7.00 Buddhism 6.22 6.00 Hinduism 5.36 5.00 Others 3.00 7.00 Place of living -1.881a 0.060a Rural 5.19 5.00 Urban 6.55 7.00 Employment status -4.157a <0.001a,* Employed 6.82 7.00 Unemployed 4.97 5.00 Education level 26.654b <0.001b,* No formal education 3.00 3.00 Primary 5.00 5.00 Secondary 5.65 6.00

Ooi P.L., Heng Z.Y. & Boon K.Y 134 https://doi.org/10.32827/ijphcs.6.3.130

IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

Tertiary education 7.32 7.50 b b, Family income 17.666 0.001 *

A statistical difference was obtained in the knowledge score among the parents of different employment status (p-value<0.001) where employed parents performed better than unemployed parents. Knowledge score was also found significantly associated with education level of parents (p-value<0.001). Post hoc pair wise comparison with Bonferroni correction showed knowledge score was significantly higher (p-value<0.001) in parents who attained tertiary education compared with parents who attained secondary education. Significant difference was also shown in knowledge score across the groups of different family income (p-value=0.001). From post hoc pair wise comparison with Bonferroni correction, knowledge score was significantly greater (p-value=0.003) among the parents with monthly family income RM4001 and above compared with parents with monthly family income of less than RM1000. Parents with monthly family income of RM3001 to RM4000 also performed better than parents with monthly family income of less than RM1000 (p-value=0.01) (Table 3).

Table 4 Practice score across different socio-demographic parameters Parameter Practice Score Mean Median Za /χ2b value p-value Gender -0.876a 0.381a Male 6.66 7.00 Female 7.12 8.00 Age (years) 0.529b 0.912b <20 6.00 6.00 20-30 7.04 8.00 30-40 6.89 7.00 >40 7.80 8.00 Marital Status -1.359a 0.231a Married 6.97 8.00 Single 10.00 10.00 No. of preschool children 3.653b 0.161b 1-2 7.05 8.00 3-4 7.06 7.00 >4 2.50 2.50 Family size 2.739b 0.254b <4 7.24 8.00 4-6 6.88 7.50

Ooi P.L., Heng Z.Y. & Boon K.Y 135 https://doi.org/10.32827/ijphcs.6.3.130

IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

>6 5.38 6.50 b b Race 3.569 0.312 Malay 7.18 8.00 Chinese 6.55 7.00 Indian 6.91 7.00 Others 4.00 4.00 Religion 2.283b 0.516b Islam 7.15 8.00 Buddhism 6.48 7.00 Hinduism 7.00 7.00 Others 6.40 6.00 Place of living -1.485a 0.138a Rural 6.06 7.00 Urban 7.11 8.00 Employment status -0.282a 0.778a Employed 7.01 8.00 Unemployed 6.94 7.00 Education level 12.548b 0.006b,* No formal education 3.00 3.00 Primary 9.00 9.00 Secondary 6.38 7.00 Tertiary education 7.72 8.00 Family income 12.505b 0.014b,*

Practice score was found significantly different among the groups of education level (p- value=0.006). Post hoc pair wise comparison with Bonferroni correction showed practice score was significantly higher (p-value=0.009) in parents who attained tertiary education compared with parents who attained secondary education. Statistical difference was also shown in practice score across the groups of different family income (p-value=0.014). From post hoc pair wise comparison with Bonferroni correction, practice score was significantly higher (p-value=0.012) among the parents with monthly family income RM4001 and above compared with parents with monthly family income of RM1001 to RM2000 (Table 4).

3.4 Correlation between Knowledge Score and Practice Score

The parents’ knowledge score was positively associated with the practice score regarding childhood immunization (Spearman's correlation coefficient, r = 0.291; p-value <0.001).

Ooi P.L., Heng Z.Y. & Boon K.Y 136 https://doi.org/10.32827/ijphcs.6.3.130

IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

4.0 Discussion

In this study, the knowledge and practice scores among parents were 6.40 and 6.99 respectively. Approximate the same results were shown in studies in Pahang state of Malaysia and Iraq (Awadh et al., 2014; Al-lela, Bahari, Al-abbassi, & Basher, 2011). These results showed that there is still room for improvement in parents’ knowledge and practice regarding childhood immunization awareness.

Insignificant associations were found in knowledge and practice scores among parents of different gender in this study. These results are similar to the findings in other studies in different regions of Malaysia (Awadh et al., 2014; Abdullah, NorAfiah, & Rosliza, 2016). Our study findings might reflect that both male and female have equal access to immunization information in Malaysia.

This study showed no significant differences in knowledge and practice scores among parents of different age, marital status, number of pre-school children and family size. However, older parents were found significantly associated with better knowledge and practice in other studies (Awadh et al., 2014; Al-lela et al., 2014; Ibnouf, Van den Borne, & Maarse, 2007; Bbaale, 2013; Borràs et al., 2009). Inconsistent results also were observed in studies conducted in Iraq and Korea in which married parents have better immunization knowledge and practice (Al-lela et al., 2014; Kim & Lee, 2011). For number of pre-school children and family size, significant associations with parents’ knowledge and practice scores also were noted in studies in other countries (Gust et al., 2004; Roodpeyma, Kamali, Babai, & Tajik, 2007; Adem, Tacettin, Sevin, & Vildan, 2003; Ozcirpici et al., 2006; Kim & Lee, 2011; Munthali, 2007). Different findings were discovered might caused by different study population or limited sample size in the study.

Insignificant associations between immunization knowledge and practice scores with parents’ race and religion were observed in this study. These findings are consistent with study done in Pahang state of Malaysia (Awadh et al., 2014). Nevertheless, studies in Netherland and North India found significant differences between ethnic and religion with immunization status (Mollema et al., 2012; Kumar, Aggarwal, & Gomber, 2010). The findings in our study indicated that there could be no different in the social environment for education, health and childcare among peoples with different race or religions in Malaysia.

Knowledge and practice scores were not associated with place of living in this study. In spite of that, study in Pahang state of Malaysia exposed that parents who were living in rural areas had lower knowledge and practice scores (Awadh et al., 2014). Lower immunization rates also were found in rural areas in many studies conducted in other countries most likely due to unequal rural–urban immunization coverage (Ibnouf et al., 2007; Kim & Lee, 2011; Kumar et al., 2010; Munthali, 2007; Ozcirpici et al., 2006). There are less health facilities in the rural areas and parents staying in rural area have difficulty to access to the medical institution in urban area due to long distance and travelling time. Therefore, the results in this study might suggested that health facilities that providing vaccination service are sufficient in both urban and rural area in Northeast Penang Island District, Malaysia.

Ooi P.L., Heng Z.Y. & Boon K.Y 137 https://doi.org/10.32827/ijphcs.6.3.130

IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

Among groups of different employment status, significant difference was noted in the knowledge score but not for practice score. In a study conducted in Canada, unemployment also was significantly associated with knowledge insufficiency (Ritvo et al., 2003). This could be due to unemployed parents usually had lower socioeconomic background and difficulty in accessibility to immunization information.

Significant differences were found in both parents’ knowledge and practice scores among groups of different education level in this study. The findings are consistent with many studies in which immunization knowledge and practice were increased with parent educational level (Al-lela et al., 2014; Ritvo et al., 2003; Borràs et al., 2009; Abdullah et al., 2016; Ibnouf et al., 2007; Bondy, Thind, Koval, & Speechley, 2009; Adem et al., 2003; Torun & Bakirci, 2006; Ozcirpici et al., 2006; Kim & Lee, 2011; Kumar et al., 2010; Bbaale, 2013; Munthali, 2007; Mollema et al., 2012). The level of education might affect the information regarding immunization risks and benefits received by parents. Parents with higher educational levels usually are in a better position to understand the importance of vaccination. With adequate immunization information, educated parents also are less worry about vaccine safety and have greater confidence in medical practitioners.

Parents’ knowledge and practice scores were observed associated with family income. Similar to this study, knowledge and practice scores were positively associated with family income in the study in Iraq (Al-lela et al., 2014). Parents whose children were underimmunized also were more likely to make lower income compared with parents whose children were fully immunized in the studies in United State, Korea and Netherland (Gust et al., 2004; Kim & Lee, 2011; Mollema et al., 2012). Low family income could be a problem faced by many parents that adversely affect their ability to complete their children’s vaccination. Parents with low family incomes are more likely to experience barriers, such as transportation or access to health care services that make adherent to vaccination schedule difficult. Nevertheless, there were no significant differences in immunization knowledge and practice among parents of different family income in studies conducted in other states of Malaysia (Awadh et al., 2014; Abdullah et al., 2016).

Significant positive relationship between parents’ knowledge level and their practice level was noted in this study. This showed that higher knowledge regarding immunization was correlated with better practice towards immunization among the parents. However, spearman's correlation coefficient was only 0.291 which showed that there was only low degree of correlation. This might due to there were other factors that proven impact on practice in other studies (Mollema et al., 2012; Manjunath & Pareek, 2003; Abdullah et al., 2016; Kennedy, Brown, & Gust, 2005). This finding is consistent with the results in the studies conducted in Pahang and Selangor state of Malaysia (Awadh et al., 2014; Abdullah et al., 2016). Lower parental knowledge about vaccination was also found associated with poorer vaccination coverage in studies carried out in other countries (Anjum et al., 2004; Ibnouf et al., 2007; Borràs et al., 2009; Al-lela et al., 2011). Therefore, increasing parents’ knowledge regarding vaccination through health education is required to improve immunization status.

Limitation of this study, it only targeted parents in health clinics in District of Northeast Penang Island. Convenient sampling further limits the generalizability of the findings.

Ooi P.L., Heng Z.Y. & Boon K.Y 138 https://doi.org/10.32827/ijphcs.6.3.130

IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

5.0 Conclusion and recommendation

This study revealed that efforts are still required to enhance parents’ knowledge and practice regarding childhood immunization awareness. The parents’ knowledge and practice in this study were associated with factors included employment status, education level and family income. Effective education programs or immunization campaigns shall be designed to target the high risk populations. It is essential that vaccination information is provided at every parent’s level of understanding especially as regards those with a low literacy level. Home visit or mobile clinic also can be conducted to improve access to vaccines among high risk populations.

Acknowledgement

This study was approved by the Medical Research Ethics Committee (MREC), Ministry of Health Malaysia. All the information was collected with the permission of the Director of Northeast Penang Island District Health Office. The authors would like to acknowledge the pharmacists in the clinics and the parents who agreed to participate in this study for their cooperation and support during data collection. The authors also would like to thank the Chief Pharmacist of Northeast Penang Island District Health Office for the support throughout this study. The authors would like to thank the Director General of Health Malaysia for permission to publish this study.

Declaration

Author(s) declare that there is no conflict of interest regarding publication of this study.

Authors’ contribution

Author 1: Designed research project, obtained ethical approval, revised and edited manuscript

Author 2: Drafted manuscript, read and approved the final manuscript

Author 3: Analyzed data, read and approved the final manuscript

Ooi P.L., Heng Z.Y. & Boon K.Y 139 https://doi.org/10.32827/ijphcs.6.3.130

IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

References

Abdullah, A.C., NorAfiah M.Z., & Rosliza A.M. (2016). Practice of childhood immunizations among parents and their assocated factors in Hulu Langat, Selangor, Malaysia. Int J Public Health and Clinical Sciences, 3:6.

Adem, A., Tacettin, I., Sevin, A., & Vildan, E. (2003). Diphtheria immunization rates and the effect of several sociodemographic factors on immunization of children in eastern Turkey. Pediatr Int, 45(4):461-6.

Al-lela, O.Q., Bahari, M.B., Al-abbassi, M.G., & Basher, A.Y. (2011). Development of a questionnaire on knowledge, attitude and practice about immunization among Iraqi parents. J Public Health, 19(6):497–503.

Al-lela, O.Q., Bahari, M.B., Salih, M.R., Al-abbassi, M.G., Elkalmi, R.M., & Jamshed, S.Q. (2014). Factors underlying inadequate parents’ awareness regarding paediatrics immunization: findings of cross-sectional study in Mosul-Iraq. BMC Pediatrics, 14(1):29. https://doi.org/10.1186/1471-2431-14-29

Anjum, Q., Omair, A., Inam, S.N., Ahmed, Y., Usman, Y., & Shaikh, S. (2004). Improving vaccination status of children under five through health education. J Pak Med Assoc, 54(12):610-3.

Awadh, A.I., Hassali, M.A., Al-lela, O.Q., Bux, S.H., Elkalmi, R.M., & Hadi, H. (2014). Immunization knowledge and practice among Malaysian parents: a questionnaire development and pilot-testing. BMC Public Health, 14:1107. https://doi.org/10.1186/1471 2458-141107

Bbaale, E. (2013). Factors Influencing Childhood Immunization in Uganda. J Health Popul Nutr, 31(1): 118–129.

Bondy, J.N., Thind, A., Koval, J.J., & Speechley, K.N. (2009). Identifying the determinants of childhood immunization in Philippines. Vaccine, 27(1): 169-75. https://doi.org/10.1016/j.vaccine.2008.08.042

Borràs, E., Domínguez, A., Fuentes, M., Batalla, J., Cardeñosa, N., & Plasencia, A. (2009). Parental knowledge of paediatric vaccination. BMC Public Health, 9:154. https://doi.org/10.1186/1471-2458-9-154

Centers for Disease Control and Prevention (1999). Achievements in Public Health, 1900 1999 Impact of Vaccines Universally Recommended for Children -- United States, 1990 1998. MMWR, 48(12); 243-248. Retrieve from https://www.cdc.gov/mmwr/preview/mmwrhtml/00056803.htm

Gangarosa, E.J., Galazka, A.M., Wolfe, C.R., Phillips, L.M., Gangarosa, R.E., Miller, E., & Chen, R.T. (1998). Impact of anti-vaccine movements on pertussis control: the untold story. Lancet, 351: 356–361. Ooi P.L., Heng Z.Y. & Boon K.Y 140 https://doi.org/10.32827/ijphcs.6.3.130

IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

Gust, D.A., Strine, T.W., Maurice, E., Smith, P., Yusuf, H., Wilkinson, M., . . . Schwartz, B. (2004). Underimmunization among children: effects of vaccine safety concerns on immunization status. Pediatrics, 114(1):e16-22. https://doi.org/10.1542/peds.114.1.e16

Ministry of Health Malaysia (2017). Health Facts 2017. Retrieve from https://mpaeds.my/wp-content/uploads/2018/03/MOH-Health-Facts-2017.pdf

Ibnouf, A., Van den Borne, H., & Maarse, J. (2007). Factors influencing immunization coverage among children under five years of age in Khartoum State, Sudan: original research. S Afr Fam Pract, 49(8):14. 14a-14f. https://doi.org/10.1080/20786204.2007.10873611

Kennedy, A.M., Brown, C.J., & Gust, D.A. (2005). Vaccine beliefs of parents who oppose compulsory vaccination. Public Health Rep, 120(3):252-8. https://doi.org/10.1177/003335490512000306

Kim, E.Y., & Lee, M.S. (2011). Related factors of age-appropriate immunization among urban-rural children aged 24-35 months in a 2005 population-based survey in Nonsan, Korea. Yonsei Med J, 52(1):104-12. https://doi.org/10.3349/ymj.2011.52.1.104

Kumar, D., Aggarwal, A., & Gomber, S. (2010). Immunization status of children admitted to a tertiary-care hospital of North India: Reasons for Partial Immunization or Non immunization. J Health Popul Nutr, 28: 300-304.

LaMorte, W.W. (2016). Power and Sample Size Determination. Boston University School of Public Health. Retrieve from http://sphweb.bumc.bu.edu/otlt/MPH-Modules/BS/BS704_Power/BS704_Power3.html

Manjunath, U., & Pareek, R. (2003). Maternal knowledge and perceptions about the routine immunization programme–a study in a semiurban area in Rajasthan. Indian J Med Sci, 57(4):158–163.

Mollema, L., Wijers, N., Hahné, S.J., van der Klis, F.R., Boshuizen, H.C., & de Melker, H.E. (2012). Participation in and attitude towards the national immunization program in the Netherlands: data from population-based questionnaires. BMC Public Health, 12:57. https://doi.org/10.1186/1471-2458-12-57

Munthali, A.C. (2007). Determinants of vaccination coverage in Malawi: evidence from the demographic and health surveys. Malawi Med J, 19 (2):79–82.

Ozcirpici, B., Sahinoz, S., Ozgur, S., Bozkurt, A.I., Sahinoz, T., Ceylan, A., . . . Akkafa, F. (2006). Vaccination coverage in the South-East Anatolian Project (SEAP) region and factors influencing low coverage. Public Health, 120 (2):145-54. https://doi.org/10.1016/j.puhe.2005.04.008

Ritvo, P., Irvine, J., Klar, N., Wilson, K., Brown, L., Bremner, K.E., . . . Krahn, M.D. (2003). A Canadian national survey of attitudes and knowledge regarding preventive vaccines.

Ooi P.L., Heng Z.Y. & Boon K.Y 141 https://doi.org/10.32827/ijphcs.6.3.130

IJPHCS International Journal of Public Health and Clinical Sciences Open Access: e-Journal e-ISSN : 2289-7577. Vol. 6:No. 3 May/June 2019

Journal of Immune Based Therapies and Vaccines, 1(1):3. https://doi.org/10.1186/1476-8518-1-3

Roodpeyma, S., Kamali, Z., Babai, R., & Tajik, Z. (2007). Mothers and vaccination: knowledge, attitudes, and practice in Iran. J Pediatr Infect, 2(1):29–34. https://doi.org/10.1055/s0035-1557016

Smith, M.J., Woods, C.R., & Marshall, G.S. (2009). Parental vaccine concerns in Kentucky. J Ky Med Assoc, 107(9): 342-349.

Torun, S.D., & Bakirci, N. (2006). Vaccination coverage and reasons for non-vaccination in a district of Istanbul. BMC Public Health, 6:125. https://doi.org/10.1186/1471-2458-6-125

Zimmerman, R.K., Wolfe, R.M., Fox, D.E., Fox, J.R., Nowalk, M.P., Troy, J.A., & Sharp L.K. (2005). Vaccine criticism on the World Wide Web. J Med Internet Res, 7(2):e17. https://doi.org/10.2196/jmir.7.2.e17

Ooi P.L., Heng Z.Y. & Boon K.Y 142 https://doi.org/10.32827/ijphcs.6.3.130