immunization coverage have experienced an age shift of diphtheria cases towards older children and adolescents [8-10]. This is because there has been > 90% coverage in birth cohorts since 2014 but gaps in booster dose coverage are widely prevalent. This has resulted in waning immunity following the primary series of diphtheria vaccinations [11,12]. Lack of awareness among the primary care physicians leading to a delay in clinical diagnosis can also be a possible reason for delayed reporting and management of cases [13].

Figure 1: Showing graphical representation of diphtheria cases over the last few years as reported by Global Health Observatory Data Repository, WHO [7]

Table 1: Showing data on Indian states exhibiting maximum cases and deaths due to diphtheria in the past few years [1]

Studies have reported that national data on coverage of boosters is not routinely collected and people often remain partially immunized [1,14-17]. To add more fuel to the fire, certain faith-based organizations consider vaccines as ‘interventions by westerners’ to destroy certain communities and taking them would lead to impotence [15,17]. Persistence of these factors undermine the efforts of the government to yield any fruitful results regarding elimination of vaccine preventable diseases.

Experts around the world have continuously warned regarding the growing number of antimicrobial genes in this bacterium making it resistant to a number of antibiotics [18]. Disrupted childhood vaccination schedules due to the COVID-19 pandemic have made the situation worse. Studies around the world have shown a resurgence of diphtheria cases post the pandemic in countries such as India, Peru, Pakistan, and Nigeria [19].

The 2016 Kerala outbreak in India showed that about 79% of the cases occurred in persons more than 10 years of age. As evidenced by the diphtheria epidemics in South America and Eastern Europe, immunity is attenuated after a few years of the primary series of childhood vaccinations. These regions eventually shifted to Td (tetanus and adult diphtheria) vaccinations for older children, adolescents, and pregnant women which resulted in a marked decrease in diphtheria cases [20].

Table 2: Showing the summary of diphtheria cases and deaths in the year 2024

Current Recommendations for Diphtheria Prophylaxis

WHO in its deliberations of the Strategic Advisory Group of Experts (SAGE) in 2002 and 2016 along with its tetanus vaccine position paper of 2017, has time and again emphasized the replacement of TT (tetanus toxoid) with Td. This was taken up by the National Technical Advisory Group on Immunization (NTAGI), Ministry of Health and Family Welfare, Government of India, which led to the introduction of the Td vaccine in India’s immunization program of all age groups including pregnant women [20].

The Universal Immunization Program (UIP) offers diphtheria vaccine at 6, 10, and 14 weeks of age as a pentavalent vaccine. This is followed by DPT (diphtheria, pertussis and tetanus) boosters at 16-24 months and 5-6 years of age. Then it is given as a Td booster at 10 years and 16 years to tackle the waning immunity. During pregnancy, Td is given in two doses 1 month apart in primigravida and a single booster shot in multigravida if previous doses were taken within the last 3 years [21].

Future Perspectives and the Road Ahead

Researchers from India, Russia, and the UK have used genomics for mapping diphtheria and have included a subset from India, which was home to half of the globally reported cases in the year 2018. They built a phylogenetic tree by combining 61 bacteria isolated from cases with 441 publicly available genomes that were collected from around the world in 122 years. The presence of antimicrobial resistance genes, mode of spread, and toxin variation were assessed [22].

Plugging the bottlenecks in the routine delivery of immunization especially in marginalised and underserved strata of the population is essential to prevent outbreaks of vaccine preventable diseases. There is a dire need to raise awareness amongst primary care physicians to keep a high index of clinical suspicion when managing membranous tonsillitis cases. Opportunities to provide diphtheria vaccination in adolescents and adults should be encouraged. Targeted interventions for increasing vaccine acceptance in certain religions with high vaccine hesitancy should be encouraged. The involvement of religious leaders, community influencers, and educational institutions can be beneficial. A study on the Kerala outbreaks of 2016, also highlighted the need for strengthening laboratory supported vaccine preventable diseases’ (VPD) surveillance [8].

It is crucial to monitor diphtheria closely, or we risk a major epidemic in a more adapted and modified form. Routine immunization with an emphasis on coverage of booster doses continues to be the most effective way of preventing resurgence of diphtheria. Strengthening of the health systems at the grassroot levels is the need of the hour.

Supporting information

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Ethical Considerations

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Acknowledgments

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Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Author contribution statement

Conceptualization; writing original draft; formal analysis; review and editing: Drishti Sagar

Data availability statement

Data included in article/supp. material/referenced in article.

Additional information

No additional information is available for this paper.

Declaration of competing interest

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

References