Serological survey on the immunity to diphtheria of the northern Greek population

Seroprevalence of an antibody against diphtheria, tetanus, and pertussis among the elderly in Khon Kaen, Thailand

BACKGROUND

Owing to a declining birth rate and longer lifespan, the number of elderly people (≥ 60 years) in Thailand has grown rapidly. However, the elderly are at significant risk of infectious diseases because they have never been immunized, because they have not been completely immunized, or because their immunity has waned. Immunity against infectious diseases in the elderly is an important means of controlling diseases in the community. Our objective was to evaluate the seroprotective rate against diphtheria, tetanus, and pertussis in the elderly Thai population.

METHODS

In total, 430 healthy individuals from the northeastern region of Thailand were enrolled in this study and stratified into five age groups: 60-65, 66-70, 71-75, 76-80, and > 80 years. Serum samples were collected and quantitatively analyzed for diphtheria, tetanus, and pertussis IgG antibody by using commercial ELISA kits. For anti-diphtheria toxoid and anti-tetanus toxoid ELISA, values < 0.01 IU/ml were interpreted as seronegative, and for anti-Bordetella pertussis toxin ELISA, values < 5 IU/ml were interpreted as seronegative; these definitions were in accord with previous studies.

RESULTS

For diphtheria toxoid Ab, the majority of the population had antibody levels > 0.01 IU/ml. For tetanus anti-toxoid Ab, the majority of the population had antibody levels of > 0.01 IU/ml, of which approximately 34% had durable antibody protection levels (DAPL) of ≥ 1 IU/ml. Meanwhile, nearly 45% of the population had an Ab level against pertussis lower than the protectivity level.

CONCLUSIONS

In total, 97.2%, 83.5%, and 55.8% of the population had a higher antibody level than the minimal protective level for diphtheria, tetanus, and pertussis, respectively. In order to prevent an outbreak of these diseases in the future, the elderly should be administered with Tdap revaccination to provide diphtheria herd immunity in the population; this will increase cocoon phenomenon for pertussis and protect the population from tetanus-prone injury.

Seroprevalence of Antibody Against Diphtheria Among the Population in Khon Kaen Province, Thailand

To assess diphtheria immunity in the northeastern region of Thailand, a seroepidemiological survey was undertaken in 2011 from 516 healthy individuals (age range 2-87 years) in Khon Kaen province. Diphtheria antitoxin levels were measured by enzyme-linked immunosorbent assay and titers of ≥0.1 IU/mL were considered to be protective antitoxin levels. Among the studied population, 94.8% have fully protective levels. The younger population (age range 2-19 years) has higher diphtheria immunity with seroprotection rates of 96.8% to 97.9%, compared with the adult population. The proportion of protective diphtheria antitoxin levels declines to 88.3% to 91.9% in the middle-aged group (20-50 years), and appeared to be higher again in the older age-group (50-70 years). To avoid epidemic spreading, promoting immunization booster programs will be helpful, especially among the adult population (20-50 years). Finally, this study may serve as a valuable guide in deciding exactly which age-groups should be targeted by such an effort.

A review of the international issues surrounding the availability and demand for diphtheria antitoxin for therapeutic use

Diphtheria treatment requires early administration of diphtheria antitoxin (DAT), an immunoglobulin preparation that neutralises circulating diphtheria toxin. Here, we review issues relating to the supply and use of DAT and assess its availability by means of an international survey. Results showed that several countries do not currently hold DAT stockpiles due to low prevalence, and hence perceived risk of diphtheria, and/or difficulties in obtaining DAT supplies. The potential for importation of cases into any country exists globally, since diphtheria remains endemic in many regions. It is therefore important that DAT be readily available - particularly since waning diphtheria immunity has been observed among adult populations in countries with good vaccination coverage. Options for diphtheria therapy are discussed.

Evaluation of human antibody responses to diphtheria toxin subunits A and B in various age groups

This study aimed to evaluate human antibody responses to diphtheria toxin subunits in various age groups. Antibodies against the intact diphtheria toxin and the diphtheria toxin subunits A and B were evaluated in 1319 individuals using a double-antigen ELISA. Although high levels of protection (83.6%, 95% CI 79.2-87.4) were found in children and adolescents, the middle-aged adult population was less protected (28.8%, 95% CI 24.3-33.6). An increase in age was associated with a decrease in the frequency of protected individuals in the 0-39-year age group (p <0.001). Anti-subunit B levels correlated well (p <0.01) with levels of antibodies against the intact toxin. In children aged < or =16 years, the intervals at which the peaks in geometric mean titres of anti-subunit B antibodies were observed were found to correlate with the ages at which booster doses are administered. Overall, males appeared to be more protected than females (OR 1.67, 95% CI 1.34-2.08, p <0.001). A small group of individuals had antibody levels of > or =0.1 IU/mL against the intact toxin, but did not have protective antibody against subunit B. Determination of anti-subunit B antibody levels should help in evaluating the effectiveness of diphtheria boosters and other aspects of diphtheria immunity.

Environmentally and occupationally acquired diseases in adolescents and adulthood: control of diphtheria, tetanus, pertussis, and poliomyelitis through regular booster vaccinations--a European perspective

Despite the success of childhood vaccination in industrialized countries, diphtheria, tetanus, pertussis (whooping cough), and poliomyelitis (polio) still affect adults and adolescents whose immunity has waned. The resurgence in the 1990s of diphtheria in the area of the former Soviet Union and its subsequent control with immunization campaigns, demonstrates the value of continued adult vaccination. Tetanus cannot be eradicated from the soil reservoir, necessitating routine primary vaccination and regular booster doses to maintain protective immunity. Although Europe has been certified endogenous polio-free since June 2002, polio imported from endemic areas continues to pose a serious threat for vulnerable populations. Booster polio vaccination is required in adolescence and adulthood. Pertussis among adults and adolescents is underestimated, representing a considerable health burden. The consequences can be more serious as this pool of susceptible adolescents and adults is a major source of pertussis transmission to newborns not yet protected by vaccination. The now available acellular pertussis-based combination vaccine covering diphtheria, tetanus, polio, and pertussis, suitable for adults and adolescents, provides the ideal tool for implementing booster immunization programs. Strong recommendations for adolescent and adult boosters are needed to overcome the continued threat of these diseases.

Vaccination coverage among adolescents in certain provinces of Greece

AIM

To estimate the vaccination coverage in a sample of adolescents in Greece.

METHODS

Vaccination status was estimated in 483 adolescents aged 15-19 y in four prefectures. The criteria for full vaccination were based on the recommendations of the Greek National Vaccination Schedule.

RESULTS

The participation rate in the study was 78.7% (380/483 adolescents). The rates of full vaccination were 94.2% for poliomyelitis, 78.4% for hepatitis B, 77.4% for BCG, 65.0% for tetanus and 54.4% for diphtheria. The rates of full vaccination for measles, rubella and mumps were 65.0%, 57.6%, and 56.0%, respectively. For pertussis, the full vaccination rate was only 36.0%, and 7.1% of the study population was totally unvaccinated. The most missed dose for all vaccines was the final booster dose, which is usually administered in older children or adolescents.

CONCLUSION

Adolescent vaccination coverage was not satisfactory in this study, mainly due to non-compliance to the final booster dose. Completion of missing vaccines at this age represents the last opportunity for massive intervention and would be of essential value for individual and community protection against common preventable diseases.

Evaluation of diphtheria convalescent patients to serve as donors for the production of anti-diphtheria immunoglobulin preparations

AIMS

The study was conducted to evaluate the possibility of selecting convalescent diphtheria patients to serve in emergency situations as donors for the production of anti-diphtheria immunoglobulin. To select suitable donors, the criterion of an antitoxin titer >/=3.0 IU/ml was used. In addition, the effects of treatment and the effect of immunization with diphtheria toxoid on the level of anti-diphtheria toxin antibodies were evaluated.

SCOPE

Three groups of diphtheria patients were included in the study. The first group (n = 23) consisted of patients who had a basic antibiotic treatment, with or without serotherapy using horse antitoxin and/or human immunoglobulin. The second group (n = 12) comprised patients examined immediately after the onset of disease. The immunological history of this group was not known. The third group (n = 20) included patients with a known immunization history, treated only with antibiotics but having received a booster immunization with diphtheria toxoid. Antitoxin titers were measured using the toxin binding inhibition (ToBI) assay.

CONCLUSIONS

In the first group, 47.8% (11/23) of the patients had a diphtheria antibody titer >/=3.0 IU/ml. For most of them, however, the antibody titers could have resulted from treatment with exogenous antibodies from horse antitoxin or human immunoglobulin (18/23). Only two of the 11 high-titer subjects had received antibiotics only. Among the second group, only two (16.76%) of the patients had an antibody titer of >/=3.0 IU/ml. In the third group 50% (10/20) of the patients showed an antibody titer of >/=3.0 IU/ml prior to vaccination, and therefore could be directly considered as donors. Three weeks after booster vaccination, 70% (14/20) had an antibody titer of >/=3.0 IU/ml and 1 year after booster vaccination, 28.6% (2/7) of the subjects still had titers of >/=3.0 IU/ml. In 40% of these patients, a decrease was observed 3-4 weeks after the booster dose. It was concluded that convalescent diphtheria patients could be considered as donors in an emergency situation, since approximately half of them showed antitoxin titers of >/=3.0 IU/ml.