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 Table of Contents  
Year : 2022  |  Volume : 66  |  Issue : 3  |  Page : 381-382  

Immunity to diphtheria among medical students of a tertiary Hospital, North Kerala

1 Professor, Department of Microbiology, Government Medical College, Alleppey, Kerala, India
2 Associate Professor, Department of Microbiology, Government Medical College, Kozhikode, Kerala, India
3 Professor, Department of Microbiology, Government Medical College, Manjeri, Kerala, India
4 Professor, Department of Microbiology, Government Medical College, Kollam, Kerala, India

Date of Submission06-Mar-2022
Date of Decision09-Jun-2022
Date of Acceptance12-Jul-2022
Date of Web Publication22-Sep-2022

Correspondence Address:
Kalpana George
Department of Microbiology, Government Medical College, Kozhikode - 673 008, Kerala
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijph.ijph_327_22

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How to cite this article:
Kizhakkekarammel P, George K, Moorkoth AP, Raveendran G. Immunity to diphtheria among medical students of a tertiary Hospital, North Kerala. Indian J Public Health 2022;66:381-2

How to cite this URL:
Kizhakkekarammel P, George K, Moorkoth AP, Raveendran G. Immunity to diphtheria among medical students of a tertiary Hospital, North Kerala. Indian J Public Health [serial online] 2022 [cited 2023 Mar 26];66:381-2. Available from:

Dear Editor,

Diphtheria is still a disease of public health importance in India. Majority of diphtheria cases being reported globally are from India.[1] Re-emergence of diphtheria with an age shift from children to older age group has been reported from many Indian states and around the globe, which points to the waning protective antibody levels after late childhood.[2],[3] Kerala has been successful in implementing vaccination programs compared to many other states of India. Prevention of epidemics and infectious diseases cell, Kerala, has reported less than 20 diphtheria cases per year from 2010 to 2013. In 2014, no cases were reported. However, in 2015, 53 cases were reported from Kerala, the majority from Malappuram and Kozhikode districts. In the very next year (2016), 533 diphtheria cases were reported from 11 districts of Kerala and 92% of cases were in Malappuram and Kozhikode districts.[4]

It is widely accepted that immunity against diphtheria is conferred by adequate levels of antibody. Even though the exact level of protective antibodies is not defined, general consensus is that 0.1 IU/ml is protective.[5] A study was conducted at a government medical college of northern Kerala to estimate the serum protective antidiphtheria antibody levels among students who represent the young adult population of the above districts. History of childhood immunization was also collected from the participants. Antidiphtheria toxin IgG quantitation was done on serum samples of the participants (N = 596) by ELISA test. Test results were interpreted as < 0.01 IU/ml – no protective immunity (basic immunization recommended); 0.01–0.1 IU/ml – booster vaccination recommended; and > 0.1 IU/ml – good immunity. Pearson's correlation coefficient, Student's t-test, and Chi square test were used for data analysis using SPSS 16.0.

In view of the emerging diphtheria outbreak in the districts, 248 (41.6%) participants had already received Td booster vaccine and 348 (58.4%) students enrolled in the study before receiving the booster. The latter group was taken as the reference group. The mean antibody levels of the group which received Td booster/s were compared with the reference group, which was significantly high in the former group (P < 0.001). When the mean antibody levels in the students who received 1, 2, or 3 doses of Td were compared with the reference group, the group that received even a single dose of Td showed significantly high antidiphtheria antibody levels compared to the reference group. There was significant positive correlation between doses of Td and antibody levels indicating an increase in antibody levels with more number of doses (Pearson's correlation coefficient, r = 0.474, P < 0.001). In the reference group, 226 (64.9%) gave history of completed primary immunisation and protective antibody levels were detected only in 14.1 % .Out of 122 students who did not complete primary immunization, only 13.9% had protective titres. There was no statistically significant difference in antibody titres between the 2 groups (P=0.503). This demonstrates that irrespective of childhood vaccination status, immunity against Corynebacterium diphtheriae wanes over time. A significant positive correlation between Td booster dose/s and antibody levels signifies the need for periodic administration of diphtheria booster vaccine doses to prevent outbreak of fatal diphtheria in the absence of natural infections boosting immunity.


Dr. B. K. Ajitha, Associate Professor in Statistics, Government Medical College, Kozhikode.

Financial support and sponsorship

State Board for Medical Research, Kerala Government, supported the study.

Conflicts of interest

There are no conflicts of interest.

   References Top

World Health Organization: Immunization, Vaccines and Biologicals. Vaccine Preventable Diseases Vaccines Monitoring System 2020 Global Summary Reference Time Series: DIPHTHERIA. Available from: [Last acessed on 2021 Dec 31].  Back to cited text no. 1
Chandran P, Lilabi MP, Bina T, Thavody J, George S. Re-emergence of diphtheria in Kerala: The need for change in vaccination policy. Int J Community Med Public Health 2019;6:829.  Back to cited text no. 2
Galazka A. The changing epidemiology of diphtheria in the vaccine era. J Infect Dis 2000;181 Suppl 1:S2-9.  Back to cited text no. 3
Sangal L, Joshi S, Anandan S, Balaji V, Johnson J, Satapathy A, et al. Resurgence of diphtheria in North Kerala, India, 2016: Laboratory supported case-based surveillance outcomes. Front Public Health 2017;5:218.  Back to cited text no. 4
Kurugöl Z, Midyat L, Türkoğlu E, İşler A. Immunity against diphtheria among children and adults in Izmir, Turkey. Vaccine 2011;29:4341-4.  Back to cited text no. 5


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