Immunity to diphtheria among children in Northern Norway and North-Western Russia

Waning rate of immunity and duration of protective immunity against diphtheria toxoid as a function of age and number of doses: Systematic review and quantitative data analysis

Although the burden of diphtheria has declined greatly since the introduction of vaccines, sporadic outbreaks continue to be reported. WHO recommends booster doses after a primary series, but questions remain about the optimal interval between these doses. We conducted a systematic review and quantitative data analysis to quantify the duration of protective immunity after different numbers of doses. Fifteen cross-sectional seroprevalence studies provided data on geometric mean concentration (GMC). Single-year age-stratified GMCs were analyzed using a mixed-effect linear regression model with a random intercept incorporating the between-country variability. GMC was estimated to decline to 0.1 IU/ml in 2.5 years (95% CI: 0.9-4.0), 10.3 years (95% CI: 7.1-13.6), and 25.1 years (95% CI: 7.6-42.6) after receiving three, four and five doses, respectively. The results drawn from cross-sectional data collected in countries with different epidemiologies, vaccines, and schedules had several limitations. However, these analyses contribute to the discussion of optimal timing between booster doses of diphtheria toxoid-containing vaccine.

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

Diphtheria is a potentially fatal infection mostly caused by toxigenic Corynebacterium diphtheriae strains and occasionally by toxigenic C. ulcerans and C. pseudotuberculosis strains. Diphtheria is generally an acute respiratory infection, characterized by the formation of a pseudomembrane in the throat, but cutaneous infections are possible. Systemic effects, such as myocarditis and neuropathy, which are associated with increased fatality risk, are due to diphtheria toxin, an exotoxin produced by the pathogen that inhibits protein synthesis and causes cell death. Clinical diagnosis is confirmed by the isolation and identification of the causative Corynebacterium spp., usually by bacterial culture followed by enzymatic and toxin detection tests. Diphtheria can be treated with the timely administration of diphtheria antitoxin and antimicrobial therapy. Although effective vaccines are available, this disease has the potential to re-emerge in countries where the recommended vaccination programmes are not sustained, and increasing proportions of adults are becoming susceptible to diphtheria. Thousands of diphtheria cases are still reported annually from several countries in Asia and Africa, along with many outbreaks. Changes in the epidemiology of diphtheria have been reported worldwide. The prevalence of toxigenic Corynebacterium spp. highlights the need for proper clinical and epidemiological investigations to quickly identify and treat affected individuals, along with public health measures to prevent and contain the spread of this disease.

Status of diphtheria immunity in the Egyptian population

In an attempt to evaluate the levels of immunity against diphtheria in the Egyptian population, 709 healthy subjects aged 2 months-105 years and from six regions of Egypt were investigated. An ELISA was used to determine the serum concentration of anti-diphtheria IgG in each subject. Following widely-used criteria for defining levels of protection, 34.1% of the subjects were categorized as susceptible to diphtheria (with < 0.01 IU antitoxin/ml serum), 43.7% were considered to have basic protection (0.01- < 0.1 IU/ml) and only the other 22.1% appeared fully protected (> or = 0.1 IU/ml). The results revealed that most of the subjects aged 2 months-50 years had a basic or fully protective level of IgG against diphtheria, although males were slightly more likely to be unprotected than females (36.2% v. 31.6%) and certain age-groups appeared to be much more likely to be susceptible than others. If outbreaks of diphtheria like those seen in recent years in the former Soviet Union are to be avoided in Egypt, the most susceptible groups of the population need to be given booster immunizations.

Comparative seroepidemiology of diphtheria in six European countries and Israel

Serological surveys for diphtheria were conducted in six European countries including Czech Republic, Hungary, Ireland, Latvia, Luxembourg, Slovakia and one country outside Europe, Israel. For each country, a nationally representative population sample was collected across the entire age range and was tested for antibodies to diphtheria toxin. Although each national laboratory used its preferred assay, the results were all standardized to those of the in vitro neutralization test and expressed in international units (IU) which allowed comparative analyses to be performed. The results showed that increasing age is related to a gradual increase in seronegative subjects (<0·01 IU/ml of diphtheria antitoxin antibodies). This may reflect waning immunity following childhood vaccination without repeated booster vaccinations in adults. Differences in seronegativity were also found according to gender. In subjects aged 1-19 years, geometric mean titres of antitoxin are clearly related to the different vaccination schedules used in the participating countries. Although clinical disease remains rare, the susceptibility to diphtheria observed in these serosurveys highlights the importance of strengthened surveillance.

Diphtheria outbreak in Norway: lessons learned

We describe an outbreak of diphtheria in Norway that occurred in 2008 and affected 3 unvaccinated family members. The epidemic caught the public health system off-guard on most levels; the diagnosis was distrusted due to its rarity, no diphtheria anti-toxin was available, and notification procedures were not rigorously followed.

Sexual dimorphism of humoral immunity with human vaccines

It has been contended that limited data exist on sex-difference in immune response with vaccines in humans. However, a comprehensive search of the literature retrieved 97 studies with 14 vaccines influenza (7 studies), hepatitis A (15 studies), hepatitis B (50 studies), pnuemococcal polysaccaride (4 studies), diphtheria (4 studies), rubella (3 studies), measles (2 studies), yellow fever (3 studies), meningococcal A (1 study), meningococcal C (1 study), tetanus (1 study), brucella (1 study), Venezuelan equine encephalitis (1 study) and rabies (4 studies), with sex-difference in humoral (antibody) response. These differences are associated with sex-difference in the clinical efficacy of influenza, hepatitis A, hepatitis B, pneumococcal polysaccharide and diphtheria vaccines and significant adverse reactions with rubella, measles and yellow fever vaccines. The genesis of these differences is uncertain but not entirely related to gonadal hormones (differences are seen in pre-pubertal and post-menopausal subjects not on hormone replacement therapy) or female sex (males had greater serological response for pneumococcal, diphtheria, yellow fever, Venezuelan equine encephalitis and in some studies with rabies vaccine. As sex-difference in humoral immune response was seen with most vaccines which cover the spectrum of mechanisms by which infectious agents cause disease (mucosal replication, viral viraemia, bacterial bacteraemia, toxin production and neuronal invasion), it is mandatory that vaccine trialists recruit a representative sample of females and males to be able to assess sex-differences which may have clinical implications.

Seroprotection against diphtheria and tetanus among Russian and Norwegian teenagers

Russian children between 7 and 10 years of age have been shown to have significantly higher seroprotection against diphtheria compared to Norwegian children. That was due to a reinforcing dose given on entering school to Russian but not to Norwegian children. The next booster was given at the age of 11-12 years in both countries. We have compared diphtheria and tetanus antitoxin levels among 13- to 14- and 15- to 16-year-old teenagers to see if the difference was maintained among the older age group. Serum samples obtained from 106 Russian and 117 Norwegian teenagers were tested by enzyme immunoassay. The Russian and Norwegian adolescents exhibited adequate rates of protection against diphtheria with similar geometric mean antitoxin concentrations of 1.26 and 1.15 IU/ml, respectively, at 13-14 years, and 0.33 and 0.29 IU/ml at 15-16 years. Differences within the age groups were not significant. However, at 13-14 years the Norwegians were much better protected 2 years after a reinforcing dose of tetanus toxoid than the Russians who had not been boosted for 7 years. At the age of 15-16 the difference diminished and became statistically not significant.

Short-term booster effect of diphtheria toxoid in initially long-term protected individuals

The main objective of this study was to investigate the booster antibody response in individuals with initially high levels of diphtheria antitoxin. Sixty individuals eligible for the routine booster by the age of 18 years each received a single dose of 5 Lf of diphtheria toxoid in diphtheria-tetanus vaccine. A double antigen ELISA was used for the assessment of the antibody levels. Chaotropic disruption in paired ELISA was used to test antibody avidity. The ratio between initial and maximum antibody concentrations after 1 month was >10 times higher and after 6 months still four times higher in those with initial antibody levels <1 IU/ml. In individuals with initial antibody levels >/=1 IU/ml a two-fold decrease was observed after 6 months compared to the initial levels. Thus, vaccination of individuals with initial long-term protection against diphtheria (antibody levels >/=1 IU/ml) is unnecessary and should be avoided.

Mycoplasma pneumoniae and Legionella pneumophila in community-acquired lower respiratory tract infections among hospitalized children: diagnosis by real time PCR

Mycoplasma pneumoniae and Legionella pneumophila are increasingly recognized as important agents of community-acquired lower respiratory tract infections (LRTI). Mycoplasma pneumoniae has been also recognized as a cause of nosocomial infections. The aim of this study was to investigate the role of real time polymerase chain reaction (PCR) for the rapid diagnosis of these infections among hospitalized children with community-acquired LRTI. During 2001, 65 children were prospectively studied. Microbiological investigation consisted of capillary PCR with a LightCycler for M. pneumoniae and L. pneumophila in induced sputum or throat swab specimens, IgM enzyme immunoassay for M. pneumoniae and immunofluorescence for L. pneumophila in paired sera. Serology testing showed acute M. pneumoniae infection in 18 (27.5%) patients and L. pneumophila in 1 (1.5%). M. pneumoniae was also detected in sputum specimen by capillary PCR in 9 (50%) serologically diagnosed cases, including 4 (22%) with non-diagnostic IgM levels in the acute phase. Capillary PCR and IgM enzyme immunoassay diagnosed together 15 (83%) M. pneumoniae cases in the acute phase. It is concluded that M. pneumoniae is an important cause of LRTI necessitating hospitalization among children in Greece. Capillary PCR in sputum may diagnose M. pneumoniae LRTI in the acute setting and direct therapy and isolation of patients.

Extensive swelling reactions occurring after booster doses of diphtheria-tetanus-acellular pertussis vaccines

Extensive local reactions are recognized to occur after administration of the fourth and fifth booster doses of diphtheria-tetanus-acellular pertussis (DTaP) vaccines. The incidence of these reactions is being delineated by prospective studies. Retrospective evaluations suggest that entire proximal limb swelling occurs in 2 to 6 percent of children given booster doses of DTaP vaccines. The reactions subside without sequelae, but they may be misdiagnosed as cellulitis and lead to unnecessary medical intervention. The pathogenesis of these reactions probably is multifactorial. Evidence suggests that both antigen content and prevaccination immunity have roles. Important, unanswered questions are the safety of revaccinating a child who previously has had an extensive local reaction and the safety of introducing further DTaP boosters into the adolescent and adult populations.

Reactogenicity and immunogenicity of adult versus paediatric diphtheria and tetanus booster dose at 6 years of age

We evaluated the reactogenicity and immunogenicity of a booster dose of diphtheria-tetanus vaccine administered at the age of school-entry, comparing a low-dose vaccine (dT) to the standard paediatric dose (DT). Participants were randomly assigned to receive one of the two vaccines; the study was evaluator-blinded. The frequency of side-reactions was similar when comparing the two groups, except when considering local redness and swelling, which were significantly more frequent among the DT group. The post-booster geometric mean titre of diphtheria antibodies in the DT group was twice as high as that in the dT group (14.1 IU/ml versus 7.7 IU/ml; P<0.001). The higher antibody response and the comparable reactogenicity indicate that DT should be used as booster at school-entry, particularly if additional booster doses during adolescence or adulthood are not administered.