Ahmad Faudzi Yusoff1, Zatil Zahidah Mohd Sharani2, Chee Cheong Kee3, Nuur Hafizah Md Iderus2, Ahmed Syahmi Syafiq Md Zamri2, Tharmarajah Nagalingam4, Mohd Safrin Mohamad Bashaabidin2, Wan Abdul Hannan Wan Ibadullah2, Sumarni Mohd Ghazali2, Ainur Yusniza Yusof5, Yee Ming Ching5, Nurhanani Mohamed Nor5, Balqis Kamarudin5, Norazah Ahmad6, Masita Arip5. 1. SEAMEO TROPMED Malaysia, Institute for Medical Research, National Institutes of Health, Ministry of Health Malaysia, Setia Alam, 40170, Shah Alam, Selangor, Malaysia. ahmadfaudzi.y@moh.gov.my. 2. Biomedical Epidemiology Unit, Institute for Medical Research, National Institutes of Health, Ministry of Health Malaysia, Setia Alam, 40170, Shah Alam, Selangor, Malaysia. 3. Sector for Biostatistics and Data Repository, National Institutes of Health, Ministry of Health Malaysia, Setia Alam, 40170, Shah Alam, Selangor, Malaysia. 4. Infection Control Unit, Kuala Lumpur Hospital, Ministry of Health Malaysia, Jalan Pahang, 50588, Kuala Lumpur, Malaysia. 5. Allergy and Immunology Research Centre, Institute for Medical Research, National Institutes of Health, Ministry of Health Malaysia, Setia Alam, 40170, Shah Alam, Selangor, Malaysia. 6. Infectious Disease Research Centre, Institute for Medical Research, National Institutes of Health, Ministry of Health Malaysia, Setia Alam, 40170, Shah Alam, Selangor, Malaysia.
Abstract
BACKGROUND: Despite high childhood immunization coverage, sporadic cases of diphtheria have been reported in Malaysia in recent years. This study aims to evaluate the seroprevalence of diphtheria among the Malaysian population. METHODS: A total of 3317 respondents age 2 years old to 60 years old were recruited in this study from August to November 2017. Enzyme-linked immunosorbent assay (ELISA) was used to measure the level of IgG antibody against the toxoid of C. diphtheriae in the blood samples of respondents. We classified respondent antibody levels based on WHO definition, as protective (≥0.1 IU/mL) and susceptible (< 0.1 IU/mL) to C. diphtheriae infection. RESULTS: Among the 3317 respondents, 57% were susceptible (38.1% of children and 65.4% of adults) and 43% (61.9% of children and 34.6% of adults) had protective antibody levels against diphtheria. The mean antibody level peaked among individuals aged 1-2 years old (0.59 IU/mL) and 6-7 years old (0.64 IU/mL) but generally decreased with age, falling below 0.1 IU/mL at around 4-6 years old and after age 20 years old. There was a significant association between age [Children: χ2 = 43.22(df = 2),p < 0.001)], gender [Adults: χ2 = 5.58(df = 1),p = 0.018] and ethnicity [Adults: χ2 = 21.49(df = 5),p = 0.001] with diphtheria toxoid IgG antibody level. CONCLUSIONS: About 57% of the Malaysian population have inadequate immunity against diphtheria infection. This is apparently due to waning immunity following childhood vaccination without repeated booster vaccination in adults. Children at age 5-6 years old are particularly vulnerable to diphtheria infection. The booster vaccination dose normally given at 7 years should be given earlier, and an additional booster dose is recommended for high-risk adults.
BACKGROUND: Despite high childhood immunization coverage, sporadic cases of diphtheria have been reported in Malaysia in recent years. This study aims to evaluate the seroprevalence of diphtheria among the Malaysian population. METHODS: A total of 3317 respondents age 2 years old to 60 years old were recruited in this study from August to November 2017. Enzyme-linked immunosorbent assay (ELISA) was used to measure the level of IgG antibody against the toxoid of C. diphtheriae in the blood samples of respondents. We classified respondent antibody levels based on WHO definition, as protective (≥0.1 IU/mL) and susceptible (< 0.1 IU/mL) to C. diphtheriaeinfection. RESULTS: Among the 3317 respondents, 57% were susceptible (38.1% of children and 65.4% of adults) and 43% (61.9% of children and 34.6% of adults) had protective antibody levels against diphtheria. The mean antibody level peaked among individuals aged 1-2 years old (0.59 IU/mL) and 6-7 years old (0.64 IU/mL) but generally decreased with age, falling below 0.1 IU/mL at around 4-6 years old and after age 20 years old. There was a significant association between age [Children: χ2 = 43.22(df = 2),p < 0.001)], gender [Adults: χ2 = 5.58(df = 1),p = 0.018] and ethnicity [Adults: χ2 = 21.49(df = 5),p = 0.001] with diphtheria toxoid IgG antibody level. CONCLUSIONS: About 57% of the Malaysian population have inadequate immunity against diphtheria infection. This is apparently due to waning immunity following childhood vaccination without repeated booster vaccination in adults. Children at age 5-6 years old are particularly vulnerable to diphtheria infection. The booster vaccination dose normally given at 7 years should be given earlier, and an additional booster dose is recommended for high-risk adults.
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