Seroprevalence of diphtheria toxoid IgG antibodies in children, adolescents and adults in Poland

Mapping anti-diphtheria toxin antibody: a systematic review and meta-analysis with multi-level meta-regression

Diphtheria is a reemerging vaccine-preventable infection of public health concern. Pooled estimates of serum IgG anti-diphtheria antibody levels can assist in estimating the susceptible population. The objective was to estimate pooled estimate of protective IgG anti-diphtheria antibodies in population globally. We searched three databases until May 2023. We included studies reporting serum anti-diphtheria antibody titre > 0.1 IU/ml as seroprotection. NHLBI checklist was used for quality assessment. Heterogeneity was explored and resolved by statistical methods. 1720 articles were retrieved out of which 51 articles were included. The pooled seropositivity rate against diphtheria was 57%. After removal of two influential outlier studies, pooled seropositivity became 51%. The meta-regression results for age depicted that seroprevalence significantly decreased with increasing age. Subgroup analysis done on basis of geographical distribution significantly reduced heterogeneity and revealed that the Western Pacific region and African regions had lower seroprotectivity compared to other regions. Subgrouping done based on year of sample collection revealed seroprotection was lower (55.63%) between 1986 and 2005 which increased to 67.11% between 2006 and 2015 and again dropped to 45.75% between 2016 and 2023. We concluded that after 2015, the disease has reemerged globally, with seroprotection level below 50% (45.75%) and overall only half of the population being seroprotected against diphtheria. So, there is a need for reinforcement of immunity against diphtheria (supplementary vaccination) after screening for antibody titre. PROSPERO registration number CRD42023458131.

Seroprevalence of Diphtheria and Tetanus Immunoglobulin G among the General Health Population in Guangzhou, China

A seroepidemiological study was conducted in 2018 to assess diphtheria and tetanus antibodies in Guangzhou, China. Diphtheria and tetanus antibody concentrations were measured with an enzyme-linked immunosorbent assay. A total of 715 subjects were enrolled in the study. The overall diphtheria and tetanus toxoid IgG-specific antibody levels were 0.126 IU/mL (95% CI: 0.115, 0.137) and 0.210 IU/mL (95% CI: 0.185, 0.240), respectively; the overall positivity rate was 61.82% (95% CI: 58.14, 65.39) and 71.61% (95% CI: 68.3, 74.92), respectively. The diphtheria and tetanus antibody concentration was decreased by age and increased by doses. The geometric mean concentrations and positivity rate of diphtheria and tetanus antibodies were lowest and below the essential protection level in people over 14 years of age. Compared to children and adolescents, middle-aged people and the aged are at much higher risk of infection with Corynebacterium diphtheriae and Clostridium tetani. The current diphtheria and tetanus immunization schedule does not provide persistent protection after childhood. There is an urgent need to adjust the current immunization schedule.

Modifiable risk factors for diphtheria: A systematic review and meta-analysis

Objective

To identify modifiable risk factors for diphtheria and assess their strengths of association with the disease.

Methods

This review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement. Electronic databases and grey literature were searched from inception until January 2023. Studies had to report on diphtheria cases and estimates of association for at least one potential risk factor or sufficient data to calculate these. The quality of non-ecological studies was assessed using the Newcastle-Ottawa Scale (NOS), while the quality of evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria.

Results

The search yielded 37,705 papers, of which 29 were ultimately included. All the non-ecological studies were of moderate to high quality. Meta-analysis of 20 studies identified three factors increasing the risk of diphtheria: incomplete vaccination (<3 doses) (pooled odds ratio (POR) = 2.2, 95% confidence interval (CI) = 1.4-3.4); contact with a person with skin lesions (POR = 4.8, 95% CI = 2.1-10.9); and low knowledge of diphtheria (POR = 2.4, 95% CI = 1.2-4.7). Contact with a case of diphtheria; sharing a bed or bedroom; sharing utensils, cups, and glasses; infrequent bathing; and low parental education were associated with diphtheria in multiple studies. Evidence for other factors was inconclusive. The quality of evidence was low or very low for all the risk factors.

Conclusions

Findings from the review suggest that countries seeking to control diphtheria need to strengthen surveillance, improve vaccination coverage, and increase people's knowledge of the disease. Future research should focus on understudied or inconclusive risk factors.

The evaluation of anti-diphtheria toxoid antibodies in healthy population in Kon Tum, Vietnam: a population-based study

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The risk of diphtheria remains high in Kon Tum given the low seroprevalence.

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One third of community in Kon Tum have no protective antibodies to diphtheria.

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The antibodies from previous childhood vaccination gradually wane over time.

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A booster dose (5-7 years) is recommended for adolescents and adults in Vietnam.

Background

Despite diphtheria immunization are to apply an effective primary immunization in childhood and to maintain immunity throughout life. Cases of diphtheria have been reported in Viet Nam in recent years. The aim of this study was to evaluate the seroprevalence of IgG antibodies to diphtheria toxoid among healthy person population in Kon Tum, Viet Nam.

Methods

Blood samples were obtained from 2225 healthy persons aged 2-98 years collected in 2019 and 2020. Samples were tested for diphtheria toxoid antibodies by commercial Anti-Diphtheria Toxoid IgG Enzyme-Linked Immunosorbent Assay (ELISA).

Results

An antibody level of <0.01 IU/mL (susceptibility) was found in 802 (36.0%) of the 2225 subjects, 136 (6.1%) had antibody levels of 0.01–0.099 IU/mL (basic protection), and 1287 (57.8%) had antibody levels ≥0.1 IU/mL (full protection). The full protection level increased significantly in persons aged above 60 years with antibody levels of 70.6%. No significant difference in seroprotection prevalence was found according to gender, ethnicity, residence, education and occupation. The results also demonstrated that people with vaccination against diphtheria during past 10 years were found to have a high immunity (83.8%) compared to 54.8% (OR: 4.7; 95%CI: 3.8-6.5) and 60.7% (OR: 3.8; 95%CI: 2.6-5.7) in persons with no and unknown vaccination (p <0.0001).

Conclusions

The level of anti-diphtheria toxoid antibodies among children and adults in Kon Tum was low. The high risk of diphtheria outbreaks may occur among individuals lacking basic immunity against diphtheria.

Diphtheria serology in adults in Central Java and East Java, Indonesia: the importance of continuous diphtheria vaccination

Background

Vaccination increase immunity against diphtheria, yet will decrease by aging. Therefore, boosters are needed to be done regularly.

Objectives

This study aims to determine the immunity to diphtheria for the population of 16 years old and above.

Methods

The sample of study were 295 collected blood serums by Riskesdas project in 2013, the criteria was above 15 years of age and originating from the Provinces of Central Java or East Java inclusively. Immunity assessment was based on antibody titer (IgG) against diphtheria using Vero Cell cytotoxicity test. Statistical analysis was performed using the X2 test.

Results

The full protective IgG titer (>0.1 IU/ml) at the age of 16–20 years included 75% sample with a geometric mean titer (GMT) of 0.19 IU/ml. Yet, at the age of 21–60 years and > 60 years, full protective IgG titers only cover 45.5% and 33.3% sample with GMT respectively 0.06 IU / ml. Statistical analysis showed the relationship between age and immune status with p-value 0.003. Otherwise, no relationship between the status of immunity with sex and residency with p-values of 0.16 and 0.43.

Conclusions

The immune status against diphtheria at the age of above 15 years decreases with aging.

Seroprevalence of diphtheria toxoid IgG antibodies in the Malaysian population

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.

Age-Related Dynamics in Post-Vaccine Antibody Immune Response to Diphtheria and Tetanus Toxoid in Bulgarian Subjects

In this study, we investigated the age-related dynamics in post-vaccine humoral immunity to diphtheria (DT) and tetanus (TT) toxoids in the Bulgarian population. In addition, we attempted to correlate the titers of specific antibodies with the predisposition to more common infectious pathology among our study participants. The 208 individuals tested were divided into five age groups: 0-4, 4-6, 6-12, 12-17 and 17-66 years, based on the vaccines received according to the immunization schedule in Bulgaria. Vaccine response was determined by measuring the concentrations of specific IgG antibodies using commercial ELISA kits. Sufficient protective levels of diphtheria (> 0.1 IU/mL) and tetanus (> 0.15 IU/mL) antitoxin were detected in 63.5% and 85.1% of all subjects, respectively. The highest rates of protection against both TT (94.3%) and DT (79.2%) were observed in the youngest age group (0-4 years). We also observed a relatively high rate of insufficient protection (< 0.1 IU/ml) against diphtheria (36% of individuals tested across all age groups) in comparison to tetanus (14.9% of all subjects). The rate of insufficient protection against both antigens was higher among children with frequent infections. Moreover, 77.1% of the individuals having low antibody titers against the highly immunogenic tetanus toxoid, also had low levels of diphtheria antibodies. The level of seroprotection is better for tetanus than for diphtheria toxoid at any age. In conclusion, our data provide information on the level of immunity to diphtheria and tetanus among vaccinated individuals in Bulgaria and allows for the identification of persons suspected of having an immune deficiency. Additional investigations are needed in order to provide reliable recommendations for the national vaccine program and personalized vaccinations.

Phenotypic and Genotypic Correlates of Penicillin Susceptibility in Nontoxigenic Corynebacterium diphtheriae, British Columbia, Canada, 2015-2018

In 2015, the Clinical and Laboratory Standards Institute (CLSI) updated its breakpoints for penicillin susceptibility in Corynebacterium species from <1 mg/L to <0.12 mg/L. We assessed the effect of this change on C. diphtheriae susceptibility reported at an inner city, tertiary care center in Vancouver, British Columbia, Canada, during 2015–2018 and performed whole-genome sequencing to investigate phenotypic and genotypic resistance to penicillin. We identified 44/45 isolates that were intermediately susceptible to penicillin by the 2015 breakpoint, despite meeting previous CLSI criteria for susceptibility. Sequencing did not reveal β-lactam resistance genes. Multilocus sequence typing revealed a notable predominance of sequence type 76. Overall, we saw no evidence of penicillin nonsusceptibility at the phenotypic or genotypic level in C. diphtheriae isolates from our institution. The 2015 CLSI breakpoint change could cause misclassification of penicillin susceptibility in C. diphtheriae isolates, potentially leading to suboptimal antimicrobial treatment selection.

Immunity against diphtheria among children aged 5-17 years in India, 2017-18: a cross-sectional, population-based serosurvey

BACKGROUND

Diphtheria is re-emerging as a public health problem in several Indian states. Most diphtheria cases are among children older than 5 years. In this study, we aimed to estimate age-specific immunity against diphtheria in children aged 5-17 years in India.

METHODS

We used residual serum samples from a cross-sectional, population-based serosurvey for dengue infection done between June 19, 2017, and April 12, 2018, to estimate the age-group-specific seroprevalence of antibodies to diphtheria in children aged 5-17 years in India. 8309 serum samples collected from 240 clusters (122 urban and 118 rural) in 60 selected districts of 15 Indian states spread across all five geographical regions (north, northeast, east, west, and south) of India were tested for the presence of IgG antibodies against diphtheria toxoid using an ELISA. We considered children with antibody concentrations of 0·1 IU/mL or greater as immune, those with levels less than 0·01 IU/mL as non-immune (and hence susceptible to diphtheria), and those with levels in the range of 0·01 to less than 0·1 IU/mL as partially immune. We calculated the weighted proportion of children who were immune, partially immune, and non-immune, with 95% CIs, for each geographical region by age group, sex, and area of residence (urban vs rural).

FINDINGS

29·7% (95% CI 26·3-33·4) of 8309 children aged 5-17 years were immune to diphtheria, 10·5% (8·6-12·8) were non-immune, and 59·8% (56·3-63·1) were partially immune. The proportion of children aged 5-17 years who were non-immune to diphtheria ranged from 6·0% (4·2-8·3) in the south to 16·8% (11·2-24·4) in the northeast. Overall, 9·9% (7·7-12·5) of children residing in rural areas and 13·1% (10·2-16·6) residing in urban areas were non-immune to diphtheria. A higher proportion of girls than boys were non-immune to diphtheria in the northern (17·7% [12·6-24·2] vs 7·1% [4·1-11·9]; p=0·0007) and northeastern regions (20·0% [12·9-29·8] vs 12·9% [8·6-19·0]; p=0·0035).

INTERPRETATION

The findings of our serosurvey indicate that a substantial proportion of children aged 5-17 years were non-immune or partially immune to diphtheria. Transmission of diphtheria is likely to continue in India until the immunity gap is bridged through adequate coverage of primary and booster doses of diphtheria vaccine.

FUNDING

Indian Council of Medical Research.

Seroprevalences of antibodies against pertussis, diphtheria, tetanus, measles, mumps and rubella: A cross-sectional study in children following vaccination procedure in Guangzhou, China

This study investigated the concentrations and seroprevalence of immunoglobulin G (IgG) antibodies against pertussis, diphtheria, tetanus, measles, mumps and rubella among children in Guangzhou, China. We conducted a cross-sectional study focusing on the post-vaccination immune statuses of children on scheduled immunisation. Human IgG antibody against six diseases were measured using commercial enzyme-linked immunosorbent assay kits. Of 620 subjects, the male-to-female ratio was 2.04 (416/204). Seroprevalence (81.97% vs 90.20%) and IgG concentrations (686.55 IU/mL vs 884.26 IU/mL, P < 0.05) for measles, tetanus (0.94 IU/mL vs 1.21 IU/mL) and rubella (34.33 IU/mL vs 47.37 IU/mL) were all higher in females. No differences based on sex were observed in the seroprevalence and IgG concentrations for anti-pertussis antibodies, anti-diphtheria antibodies and anti-mumps. Slight increase in seroprevalence and IgG concentration occurred with anti-pertussis antibodies after primary and booster vaccinations (from 0.00% [1 m], 5.45% [6 m], to 17.14% [1.5 yr]; and from 8.57% [5 yr] to 15.79% [6 yr]). Although no booster vaccination was given after age 6 yr, the seroprevalence and IgG concentration for anti-pertussis antibodies remained relatively stable. For diphtheria, tetanus, measles and rubella, seroprevalence reached their peaks after the primary and first booster vaccination. A plateau occurred after age 1.5 yr with a declining trend in subjects >8-10 yr. The IgG concentrations of these 4 pathogens showed a dramatic increase after primary vaccination, with steadily declining trends thereafter. For mumps, subjects showed increased seroprevalence and IgG concentration after the primary mumps-containing vaccination in 1.5-yr-olds (from 7.14% to 57.14%; 52.13 IU/mL to 214.18 IU/mL); however, following that low seroprevalence levels (from 42.86% to 80.00%) were observed. The post-vaccination immune statuses against diphtheria, tetanus, measles and rubella were relatively satisfactory, compared to those against pertussis and mumps. Booster vaccination against pertussis and mumps at appropriate time should be considered.

Immunogenicity of Diphtheria Booster Vaccination in Adolescents With Inflammatory Bowel Disease

The aim of this prospective study was to assess the immunogenicity and safety of booster vaccine against diphtheria in children with inflammatory bowel disease on and without immunosuppression treatment. Immunoprotection was achieved in 93% of the children. No significant differences depending on the treatment used and no serious adverse events or flares of inflammatory bowel disease were observed.

Seroprevalence of vaccine-preventable diseases among children and adolescents in Singapore: Results from the National Paediatric Seroprevalence Survey 2018

OBJECTIVES

The Ministry of Health (MOH), Singapore, conducted the National Paediatric Seroprevalence Survey 2018 (NPSS 2018) to estimate the latest immunity levels against measles, rubella, varicella, diphtheria, tetanus and hepatitis B, and the seroprevalence of chronic hepatitis B virus (HBV) carriage in children and adolescents in Singapore.

METHODS

The survey involved prospective collection of residual sera from 1,200 children and adolescents aged 1-17 years in two public acute hospitals. Enzyme-linked immunosorbent assays (EIA) or plague reduction neutralisation tests (PRNT) were used to determine the seroprevalence of the vaccine-preventable diseases.

RESULTS

Overall prevalence of measles and rubella antibodies among Singaporean children and adolescents aged 1-17 years were 98.2% (95% CI: 91.2-98.8%) and 94.8% (95% CI: 93.4-95.9%) respectively. 97.1% (95% CI: 96.0-97.9%) of subjects had at least basic protection against diphtheria, while 89.3% (95% CI: 87.5-91.0%) were protected against tetanus. The prevalence of chronic HBV carriage was 0.4% (95% CI: 0.2-1.0%), while 45.7% (95% CI: 42.9-48.5%) were immune against HBV. The seroprevalence for varicella antibodies was 52.9% (95% CI: 50.1-55.7%). Concordance between vaccination status and seroprevalence was observed for measles, rubella, diphtheria and tetanus.

CONCLUSION

Singapore's children and adolescents are well-protected against measles, rubella, diphtheria and tetanus. Continual efforts in ensuring high vaccination coverage should be sustained.

Immune status against diphtheria in healthy adults

Outbreaks of diphtheria continue to occur in Kerala with an age shift to older population. Antibody seroprevalence studies are essential to understand the immune status of the community and to develop an effective immunization strategy.

AIM

To assess the necessity of diphtheria vaccination among adults.

SETTINGS AND DESIGN

Cross-sectional study, among 152 healthy adults (>18 years).

METHODS AND MATERIALS

Diphtheria IgG antibody detection was performed by using ELISA technique.

RESULTS

Out of 152 study population, 14 (9.2%) individuals had very low antibody levels, requiring basic immunization, 123 (80.9%) needed booster vaccination, 12 (7.9%) would need a booster dose in 5 years and 3 (2%) would need a booster dose in 7 years to maintain adequate antibody levels. Out of the total, 131 (86.2%) individuals had completed childhood immunization and 21 (13.8%) had incomplete or no immunization during childhood. In the population who had completed childhood immunization, 4 (3%) had very low antibody levels requiring basic immunization and 113 (86%) had antibody levels needing booster vaccine soon, with the remaining 14 (10.6%) individuals requiring a booster vaccine after 5 years and 7 years. In the partially immunized/unimmunized population, 10 (47.6%) had antibody levels requiring basic immunization and another 10 (47.6%) had antibody levels low enough to warrant a booster vaccine.

CONCLUSIONS

Majority of the subjects who had completed childhood immunization showed an inadequate immunity against diphtheria during adulthood. This indicates waning immunity against diphtheria. Hence, modifying the present diphtheria vaccination strategy to include booster doses during adulthood is essential.

CONTEXT

Even in developed countries where nearly 100% universal immunization is achieved, diphtheria outbreaks are known to occur. Several seroprevalence studies have been conducted in those regions to determine whether those populations have adequate levels of antibodies against diphtheria. In India, sporadic outbreaks occur, and an increasing number of diphtheria cases are being reported over the last few years. Large outbreaks in Kerala 2016 were about 533 cases. Recent outbreaks in 2019, in Trivandrum, about 175 cases were suspected and 19 cases were confirmed in laboratory. However, Indian studies to determine whether the adult population has adequate protective antibody levels are lacking. Knowing the immune status of the population and devising an appropriate strategies to prevent outbreaks of diphtheria are the integral parts of primary care. These concerns are the basis and evaluation of the seroprevalence of IgG antibody levels against diphtheria antitoxin among healthy adults in our region in this study.

Seroprevalence of diphtheria and pertussis immunoglobulin G among children with pneumonia in Ji'nan, China

BACKGROUND

Vaccination is still one of the most important methods to control and prevent childhood infections including diphtheria and pertussis. This study evaluated the level of diphtheria (DT) and pertussis (PT)-related antibodies among children with pneumonia in Ji'nan, China.

METHODS

A total of 484 sera of children from 1 day to 13 years of age were collected from 2014 to 2015 in Ji'nan. Children with recent history of pertussis were excluded from this study. Anti-DT and PT IgG concentrations were measured by ELISA (Euroimmun, Lübeck, Germany).

RESULTS

Of the 484 subjects tested, the overall positivity rate of anti-DT IgG (≥0.1 IU/ml) was 48.97%, and the highest positivity rate of anti-DT IgG (68.55%) and proportion with long term protection (23.27%) were observed in children aged 6 m- < 3 y. For anti-PT IgG, 334 subjects (69.01%) had anti-PT IgG levels below the lower limit of detection (5 IU/ml). Even with detectable anti-PT antibodies, the majority (115/150, 76.67%) of them had antibody levels of 5- < 40 IU/ml. The highest proportion of subjects with detectable anti-PT IgG (≥5 IU/ml) was observed in children aged < 6 m (44.36%), then the proportion continually decreased to 15.0% at 3 y- < 6 y (χ2 = 24.05, p < 0.0001). The highest positivity rate (≥40 IU/ml) was only 8.27% in children aged < 6 m. Subjects with an anti-PT IgG ≥100 IU/ml were observed in all the groups and there were no significant differences in the proportions of subjects with a level ≥ 100 IU/ml among these age groups (χ2 = 2.572, p = 0.4624). A total of 5 subjects had anti-PT IgG ≥100 IU/ml (≥1 years post pertussis vaccination) which was considered to be indicative of a recent pertussis infection.

CONCLUSIONS

We demonstrated low antibody levels and protection against pertussis in our study population. The anti-PT IgG maintained a low level throughout all age groups, and even no immune responses were observed after the basic immunization and booster. Our study supported the need to reevaluate the immune response of DTP vaccine which was used in Shandong province after 2010.

A single booster dose of diphtheria vaccine is effective for travelers regardless of time interval since previous doses

Our study showed the immune response before and after a booster against diphtheria given within the 20-year interval recommended in Sweden or after a prolonged interval. Of 40 travellers, 10/13 in recommended interval group were immune before booster and 19/27 with a delayed interval. After booster, 13/13 versus 26/27 were protected. One booster was sufficient to achieve immunity regardless of the interval.

Changes in MLST profiles and biotypes of Corynebacterium diphtheriae isolates from the diphtheria outbreak period to the period of invasive infections caused by nontoxigenic strains in Poland (1950-2016)

Background

Corynebacterium diphtheriae is a re-emerging pathogen in Europe causing invasive infections in vaccinated persons and classical diphtheria in unvaccinated persons. In the presented study we analysed genetic changes in C. diphtheriae isolates collected in Poland from the period before the introduction of the mass anti-diphtheria vaccination to the present time when over 98% of the population is vaccinated.

Methods

A total of 62 C. diphtheriae isolates collected in the 1950s–1960s, 1990s and 2000–2016 in Poland were investigated. Examined properties of the isolates included toxigenic status, presence of tox gene, biotype, MLST type (ST) and type of infection.

Results

A total of 12 sequence types (STs) were identified among the analysed C. diphtheriae isolates. The highest variability of STs was observed among isolates from diphtheria and asymptomatic carriers collected in the XX century. Over 95% of isolates collected from invasive and wound infections in 2004–2016 belonged to ST8. Isolates from the XX century represented all four biotypes: mitis, gravis, intermedius and belfanti, but the belfanti biotype appeared only after the epidemic in the 1990s. All except three isolates from the XXI century represented the biotype gravis.

Conclusions

During a diphtheria epidemic period, non-epidemic clones of C. diphtheriae might also disseminate and persist in a particular area after the epidemic. An increase of the anti-diphtheria antibody level in the population causes not only the elimination of toxigenic strains from the population but may also influence the reduction of diversity of C. diphtheriae isolates. MLST types do not reflect the virulence of isolates. Each ST can be represented by various virulent variants representing various pathogenic capacities, for example toxigenic non-invasive, nontoxigenic invasive and nontoxigenic non-invasive.

Does vaccination ensure protection? Assessing diphtheria and tetanus antibody levels in a population of healthy children: A cross-sectional study

Vaccination effectiveness is proven when the disease does not develop after a patient is exposed to the pathogen. In the case of rare diseases, vaccination effectiveness is assessed by monitoring specific antibody levels in the population. Such recurrent analyses allow the evaluation of vaccination programs. The primary schedule of diphtheria and tetanus vaccinations is similar in various countries, with differences mainly in the number and timing of booster doses. The aim of the study was to assess diphtheria and tetanus antibody concentrations in a population of healthy children.Diphtheria and tetanus antibody levels were analyzed in a group of 324 children aged 18 to 180 months. All children were vaccinated in accordance with the Polish vaccination schedule.Specific antibody concentrations greater than 0.1 IU/mL were considered protective against tetanus or diphtheria. Levels above 1.0 were considered to ensure long-term protection.Protective levels of diphtheria antibodies were found in 229 patients (70.46%), and of tetanus in 306 patients (94.15%). Statistically significant differences were found in tetanus antibody levels in different age groups. Mean concentrations and the percentage of children with high tetanus antibody titers increased with age. No similar correlation was found for diphtheria antibodies. High diphtheria antibody levels co-occurred in 72% of the children with high tetanus antibody levels; 95% of the children with low tetanus antibody levels had low levels of diphtheria antibodies.The percentage of children with protective diphtheria antibody levels is lower than that in the case of tetanus antibodies, both in Poland and abroad, but the high proportion of children without diphtheria protection in Poland is an exception. This is all the more puzzling when taking into account that Polish children are administered a total of 5 doses containing a high concentration of diphtheria toxoid, at intervals shorter than 5 years. The decrease in antibody titers occurring over time is a significant factor in vaccination program planning.Tetanus antibody concentrations were found to be high, but responses to the diphtheria and tetanus components were divergent. The percentage of children protected against diphtheria was significantly lower than protected against tetanus.

Immunity to Diphtheria and Tetanus in Army Personnel and Adult Civilians in Mashhad, Iran

This study aimed to investigate serologic immunity to diphtheria and tetanus in army personnel and a sample population of adult civilians in Mashhad, Iran. Army personnel (n = 180) and civilians (n = 83) who presented at Mashhad army hospital participated in this study. Diphtheria and tetanus antitoxin levels were determined by enzyme-linked immunosorbent assay. Approximately 77% and 94% of army personnel aged 18-34 years had at least basic protection against diphtheria (antitoxin level ≥0.1 IU/mL) and tetanus (antitoxin level >0.1 IU/mL), respectively. For civilians in this age group, the proportions were 76% for both diseases. Antitoxin levels waned with age. Thus, participants older than 50 years had lower immunity; this decrease in immunity was more pronounced for tetanus than for diphtheria in both army personnel and civilians. For both diseases, geometric mean antitoxin titers and the proportion of participants with at least basic protection were higher in subjects with a history of vaccination in the last 10 years (P < 0.001), higher in men than women, and in army personnel than civilians in each age group. Young army personnel and civilians (18-34 years old) had adequate immunity to diphtheria and tetanus. However, the large number of susceptible older adults (>50 years old) calls for improved booster vaccination protocols.

Long-Term Protection against Diphtheria in the Netherlands after 50 Years of Vaccination: Results from a Seroepidemiological Study

BACKGROUND AND AIMS

To evaluate the National Immunisation Programme (NIP) a population-based cross-sectional seroepidemiological study was performed in the Netherlands. We assessed diphtheria antitoxin levels in the general Dutch population and in low vaccination coverage (LVC) areas where a relatively high proportion of orthodox Protestants live who decline vaccination based on religious grounds. Results were compared with a nationwide seroepidemiological study performed 11 years earlier.

METHODS

In 2006/2007 a national serum bank was established. Blood samples were tested for diphtheria antitoxin IgG concentrations using a multiplex immunoassay for 6383 participants from the national sample (NS) and 1518 participants from LVC municipalities. A cut-off above 0.01 international units per ml (IU/ml) was used as minimum protective level.

RESULTS

In the NS 91% of the population had antibody levels above 0.01 IU/ml compared to 88% in the 1995/1996 serosurvey (p<0.05). On average, 82% (vs. 78% in the 1995/1996 serosurvey, p<0.05) of individuals from the NS born before introduction of diphtheria vaccination in the NIP and 46% (vs. 37% in the 1995/1996 serosurvey, p = 0.11) of orthodox Protestants living in LVC areas had antibody levels above 0.01 IU/ml. Linear regression analysis among fully immunized individuals (six vaccinations) without evidence of revaccination indicated a continuous decline in antibodies in both serosurveys, but geometric mean antibodies remained well above 0.01 IU/ml in all age groups.

CONCLUSIONS

The NIP provides long-term protection against diphtheria, although antibody levels decline after vaccination. As a result of natural waning immunity, a substantial proportion of individuals born before introduction of diphtheria vaccination in the NIP lack adequate levels of diphtheria antibodies. Susceptibility due to lack of vaccination is highest among strictly orthodox Protestants. The potential risk of spread of diphtheria within the geographically clustered orthodox Protestant community after introduction in the Netherlands has not disappeared, despite national long-term high vaccination coverage.

Vaccine-Derived Immunity in Children With Cancer-Analysis of Anti-Tetanus and Anti-Diphtheria Antibodies Changes after Completion of Antineoplastic Therapy

BACKGROUND

Cancer survival rates and longevity of patients after therapy have significantly improved during the last decades. Thus durable protection against infections should be provided. The aim of the study was to compare the levels of vaccine-derived antibodies in children with cancer compared to those of healthy children and to investigate how therapy influences the levels of specific antibodies.

PROCEDURE

A group of 40 children, diagnosed with acute lymphoblastic leukemia (ALL) or solid tumor (ST), followed in Poznan University of Medical Sciences Department of Pediatric Hematology, Oncology and Bone Marrow Transplantation, were recruited for evaluation of humoral immunity. Antibody levels were checked before treatment and 3, 6, and 12 months after treatment.

RESULTS

In patients with ALL or ST, levels of IgG against tetanus and diphtheria were significantly lower than in the control group. Among ALL patients, 9% remained negative for tetanus and diphtheria antibodies 12 months after therapy. Among patients with ST 3 months after chemotherapy, there were no protective antibodies in 12% against tetanus, and in 18% against diphtheria. All patients reconstituted immunity 6 and 12 months after therapy.

CONCLUSIONS

Our data show that a considerable number of cancer patients lose immunity against diphtheria and tetanus after therapy. Compared to ST, patients with ALL lose protective antibody levels more often. Patients with ST reconstituted antibodies after the treatment cessation, while levels in ALL patients remained low.

Seroprevalence and Determinants of Immunity to Diphtheria for Children Living in Two Districts of Contrasting Incidence During an Outbreak in East Java, Indonesia

BACKGROUND

In 2012, an ongoing outbreak of diphtheria in Indonesia was focused in the province of East Java. There was a need to assess vaccine coverage and immunity gaps in children.

METHODS

We conducted a cross-sectional seroprevalence and vaccine coverage survey of children 1-15 years of age in 2 districts of East Java: one of high incidence (on the island of Madura) and one of low incidence (on the mainland). From each district, we sampled 150 children (10 children per year of age). Sera and throat swabs were taken to determine immunity and carriage status. Immunity was defined as ≥0.1 international unit/mL of antibody to diphtheria toxin.

RESULTS

A total of 297 children were selected to participate in the study. Coverage of three doses of combined vaccine for diphtheria, tetanus and pertussis was significantly lower (P < 0.001) in the high incidence district compared with the low [57%, 95% confidence interval (CI): 36-78 vs. 97%, 95% CI: 93-100]. Despite this higher vaccine coverage, seroprevalence of immunity was lower in the low incidence district compared with the high (71%, 95% CI: 63-80 vs. 83%, 95% CI: 76-90). Immunity in the high incidence district was associated with increased age, increased prevalence of toxigenic Corynebacterium diphtheriae carriers and with receipt of multiple (and likely more recent) boosters.

CONCLUSIONS

Significant variation exists in vaccine coverage and seroprevalence of immunity to diphtheria in East Java. Immunity in high incidence districts is likely because of natural immunity acquired through exposure to toxigenic C. diphtheriae. Booster vaccines are essential for achieving protective levels of immunity.

Prevalence of diphtheria and tetanus antibodies among adults in Singapore: a national serological study to identify most susceptible population groups

BACKGROUND

In view of waning antitoxin titres over time after the last vaccine dose against diphtheria and tetanus, we determined the immunity levels in adults to identify most susceptible groups for protection in Singapore.

METHODS

Our study involved residual sera from 3293 adults aged 18-79 who had participated in a national health survey in 2010. IgG antibody levels were determined using commercial enzyme-linked immunosorbent assay.

RESULTS

Overall, 92.0% (95% confidence interval [CI]: 91.1-92.9%) had at least basic protection against diphtheria (antibody levels ≥0.01 IU/ml), while 71.4% (95% CI: 69.8-72.9%) had at least short-term protection against tetanus (antibody levels >0.1 IU/ml). The seroprevalence declined significantly with age for both diseases; the drop was most marked in the 50- to 59-year age group for diphtheria and 60- to 69-year age group for tetanus. There was a significant difference in seroprevalence by residency for diphtheria (92.8% among Singapore citizens versus 87.1% among permanent residents; P = 0.001). The seroprevalence for tetanus was significantly higher among males (83.2%) than females (62.4%) (P < 0.0005).

CONCLUSIONS

It may be of value to consider additional vaccination efforts to protect older adults at higher risk for exposure against diphtheria and tetanus, particularly those travelling to areas where diphtheria is endemic or epidemic.