Diphtheria: changing patterns in the developing world and the industrialized world

Regional differences in historical diphtheria and scarlet fever notification rates in The Netherlands, 1905-1925: a spatial-temporal analysis

BACKGROUND

We describe how rates of two frequently occurring notifiable diseases-diphtheria and scarlet fever-varied between regions of The Netherlands in the early twentieth century, and identify potential factors underlying this variation.

METHODS

Digitized weekly mandatory notification data for 1905-1925, municipality level, were aggregated into 27 'spatial units' defined by unique combinations of province and population density category (high: more than 4500; mid : 1250-4500; low: less than 1250 inhabitants km-2). Generalized additive regression models were fitted to estimate the associations between notification rates and population density, infant mortality rate and household income, while adjusting for temporal trends per spatial unit.

RESULTS

Annual per capita notification rates for both diphtheria and scarlet fever tended to rise from the beginning of the period 1905-1925 until peaking around 1918/1919. Adjusted diphtheria notification rates were higher for high- and mid- compared with low-density municipalities (by 71.6 cases per 100 000, 95% confidence interval (CI) : 52.7-90.5; 39.0/100 k, 95% CI : 24.7-53.3, respectively). Scarlet fever showed similar associations with population density (35.7 cases per 100 000, 95% CI : 9.4-62.0; 21.4/100 k, 95% CI: 1.5-41.3).

CONCLUSIONS

There was considerable spatial variation in notification rates for both diseases in early twentieth century Netherlands, which could partly be explained by factors capturing variation in living conditions and socio-economic circumstances. These findings aid understanding of contemporary respiratory infection transmission.

Microbiological and Clinical Aspects of Diphtheria-Confirmed Cases from Capital City of Indonesia, Jakarta, and Surrounding Areas in 2017

Background: The World Health Organization reported Indonesia as one of the countries with the most prevalent cases of diphtheria worldwide. The microbiological aspects of diphtheria-inducing bacteria are of great significance in tracing disease transmission and case management. However, clinical aspects are critical for updating clinical features and case management in the field, which may sometimes differ from theoretical foundations. Objectives: This study aimed to identify the microbiological and clinical aspects, including molecular typing and case fatality rates, in diphtheria-confirmed cases from the capital city of Indonesia, Jakarta, and surrounding areas in 2017. Methods: The microbiological aspect of 40 diphtheria-confirmed cases were obtained by re-identify diphtheria-inducing bacteria isolated from the samples, while the clinical aspects of the cases were obtained from the medical records and epidemiological data. The chi-square test was used to examine the correlation between fatal cases and myocarditis and diphtheria antitoxin administration delay. In this study, P ≤ 0.05 was set as the significance level. Results: All 40 diphtheria confirmed cases were induced by toxigenic Corynebacterium diphtheriae with two biotypes, namely intermedius (60.0%) and mitis (40.0%). There are six sequence types of bacteria with two main sequence types, ie, ST534 (46.4%) and ST377 (35.7%). The proportions of cases that had a fever and sore throat were 72.5% and 77.5%, respectively; however, the prevalence rates of the cases with pseudomembrane and bull neck were 100% and 47%, respectively. Most cases were administered a combination of penicillin or erythromycin with other antibiotics (40%), and 22.5% of the cases only received penicillin. Myocarditis was noticed in three fatal cases, and their relationship was statistically significant (P = 0.000). All five fatal cases (12.5% of cases) received diphtheria antitoxin (DAT) lately or had not received it yet. Conclusions: Toxigenic C. diphtheriae with two biotypes (namely mitis and intermedius) and two main sequence types (ie, ST534 and ST377) was the causative agent of diphtheria-confirmed cases from Jakarta and surrounding areas in 2017. It was also concluded that those fatal cases were correlated with myocarditis complications.

Application of Polymerase Chain Reaction in Diphtheria Laboratory Examination: A Field Need

Background: Indonesia is one of the five countries with the highest number of diphtheria cases worldwide. Diphtheria is caused by the toxigenic strains Corynebacterium diphtheriae, C. ulcerans, and C. pseudotuberculosis. The diphtheria-causing bacteria can be identified using conventional and molecular methods, including polymerase chain reaction (PCR) assay. We used the PCR assay as additional testing, because in island countries like Indonesia, specimen transport is a serious challenge to maintaining bacterial survival. Objectives: This study aimed to evaluate the PCR assay as additional testing to identify diphtheria-causing bacteria in the diphtheria laboratory. Methods: In this cross-sectional study, a total of 178 pairs of the throat and nasal swabs from diphtheria suspected cases and close contacts were collected from seven provinces in Indonesia in 2016. All samples were directly identified by the conventional method and multiplex PCR assay. Statistical analysis was conducted using the 2 × 2 tables to determine the sensitivity and specificity of both methods, while the χ2 test was used to examine the correlation between specimen examination delay and the differentiation of results. A P-value < 0.05 was considered as statistically significant. Results: Out of 178 examined samples, eight samples were identified as diphtheria-positive by both the conventional method and PCR assay, while nine samples were only detected by the PCR assay. All diphtheria-causing bacteria found in the positive samples were toxigenic C. diphtheriae. The diphtheria-causing bacteria were found in 27.6% of cases and 6.0% of close contacts using the PCR assay versus 13.8% of cases and 2.7% of close contacts using the conventional method. Statistical analysis showed that the PCR assay is about twice more sensitive than the conventional method. There was a significant correlation between the differentiation of results and > 72 hours’ specimen examination delay with a P-value of 0.04 (< 0.05). Conclusions: The PCR assay is more sensitive than the conventional method to identify diphtheria-causing bacteria and may be applied as additional testing to increase the positivity rate of diphtheria-confirmed cases in Indonesia as an archipelago country where geographical factors and specimen transport are real obstacles.

Epidemiology of Diphtheria in Yemen, 2017-2018: Surveillance Data Analysis

BACKGROUND

As a consequence of war and the collapse of the health system in Yemen, which prevented many people from accessing health facilities to obtain primary health care, vaccination coverage was affected, leading to a deadly diphtheria epidemic at the end of 2017.

OBJECTIVE

This study aimed to describe the epidemiology of diphtheria in Yemen and determine its incidence and case fatality rate.

METHODS

Data were obtained from the diphtheria surveillance program 2017-2018, using case definitions of the World Health Organization. A probable case was defined as a case involving a person having laryngitis, pharyngitis, or tonsillitis and an adherent membrane of the tonsils, pharynx, and/or nose. A confirmed case was defined as a probable case that was laboratory confirmed or linked epidemiologically to a laboratory-confirmed case. Data from the Central Statistical Organization was used to calculate the incidence per 100,000 population. A P value <.05 was considered significant.

RESULTS

A total of 2243 cases were reported during the period between July 2017 and August 2018. About 49% (1090/2243, 48.6%) of the cases were males. About 44% (978/2243, 43.6%) of the cases involved children aged 5 to 15 years. Respiratory tract infection was the predominant symptom (2044/2243, 91.1%), followed by pseudomembrane (1822/2243, 81.2%). Based on the vaccination status, the percentages of partially vaccinated, vaccinated, unvaccinated, and unknown status patients were 6.6% (148/2243), 30.8% (690/2243), 48.6% (10902243), and 14.0% (315/2243), respectively. The overall incidence of diphtheria was 8 per 100,000 population. The highest incidence was among the age group <15 years (11 per 100,000 population), and the lowest incidence was among the age group ≥15 years (5 per 100,000 population). The overall case fatality rate among all age groups was 5%, and it was higher (10%) in the age group <5 years. Five governorates that were difficult to access (Raymah, Abyan, Sa'ada, Lahj, and Al Jawf) had a very high case fatality rate (22%).

CONCLUSIONS

Diphtheria affected a large number of people in Yemen in 2017-2018. The majority of patients were partially or not vaccinated. Children aged ≤15 years were more affected, with higher fatality among children aged <5 years. Five governorates that were difficult to access had a case fatality rate twice that of the World Health Organization estimate (5%-10%). To control the diphtheria epidemic in Yemen, it is recommended to increase routine vaccination coverage and booster immunizations, increase public health awareness toward diphtheria, and strengthen the surveillance system for early detection and immediate response.

Epidemiological, clinical, and public health response characteristics of a large outbreak of diphtheria among the Rohingya population in Cox's Bazar, Bangladesh, 2017 to 2019: A retrospective study

BACKGROUND

Unrest in Myanmar in August 2017 resulted in the movement of over 700,000 Rohingya refugees to overcrowded camps in Cox's Bazar, Bangladesh. A large outbreak of diphtheria subsequently began in this population.

METHODS AND FINDINGS

Data were collected during mass vaccination campaigns (MVCs), contact tracing activities, and from 9 Diphtheria Treatment Centers (DTCs) operated by national and international organizations. These data were used to describe the epidemiological and clinical features and the control measures to prevent transmission, during the first 2 years of the outbreak. Between November 10, 2017 and November 9, 2019, 7,064 cases were reported: 285 (4.0%) laboratory-confirmed, 3,610 (51.1%) probable, and 3,169 (44.9%) suspected cases. The crude attack rate was 51.5 cases per 10,000 person-years, and epidemic doubling time was 4.4 days (95% confidence interval [CI] 4.2-4.7) during the exponential growth phase. The median age was 10 years (range 0-85), and 3,126 (44.3%) were male. The typical symptoms were sore throat (93.5%), fever (86.0%), pseudomembrane (34.7%), and gross cervical lymphadenopathy (GCL; 30.6%). Diphtheria antitoxin (DAT) was administered to 1,062 (89.0%) out of 1,193 eligible patients, with adverse reactions following among 229 (21.6%). There were 45 deaths (case fatality ratio [CFR] 0.6%). Household contacts for 5,702 (80.7%) of 7,064 cases were successfully traced. A total of 41,452 contacts were identified, of whom 40,364 (97.4%) consented to begin chemoprophylaxis; adherence was 55.0% (N = 22,218) at 3-day follow-up. Unvaccinated household contacts were vaccinated with 3 doses (with 4-week interval), while a booster dose was administered if the primary vaccination schedule had been completed. The proportion of contacts vaccinated was 64.7% overall. Three MVC rounds were conducted, with administrative coverage varying between 88.5% and 110.4%. Pentavalent vaccine was administered to those aged 6 weeks to 6 years, while tetanus and diphtheria (Td) vaccine was administered to those aged 7 years and older. Lack of adequate diagnostic capacity to confirm cases was the main limitation, with a majority of cases unconfirmed and the proportion of true diphtheria cases unknown.

CONCLUSIONS

To our knowledge, this is the largest reported diphtheria outbreak in refugee settings. We observed that high population density, poor living conditions, and fast growth rate were associated with explosive expansion of the outbreak during the initial exponential growth phase. Three rounds of mass vaccinations targeting those aged 6 weeks to 14 years were associated with only modestly reduced transmission, and additional public health measures were necessary to end the outbreak. This outbreak has a long-lasting tail, with Rt oscillating at around 1 for an extended period. An adequate global DAT stockpile needs to be maintained. All populations must have access to health services and routine vaccination, and this access must be maintained during humanitarian crises.

Diphtheria outbreak in Jakarta and Tangerang, Indonesia: Epidemiological and clinical predictor factors for death

Background

In 2017, a diphtheria outbreak occurred in several provinces in Indonesia. The aim of this study was to identify predictors of mortality outcome of pediatric patients with clinical diphtheria.

Methods

A retrospective cohort study was conducted using patient medical records at five referral hospitals in the Province of Jakarta and one in Tangerang District, Banten Province during January 2017 to 31 August 2018. All children in the age group of 1–18 years old discharged with diagnosis of clinical diphtheria formed the study group. All anonymized patient data were evaluated for demographic issues, clinical features, immunization status, complication, laboratory profiles and outcome.

Results

A total of 283 patients with clinical diphtheria were included in the study group with case fatality rate of 3.5%. All mortal patients had the complication of myocarditis. Regression analyses revealed factors for predicting mortality. Incomplete primary diphtheria toxoid immunization, stridor, bull neck, leukocytosis ≥15 x10⁹ cells/L and thrombocytopenia ≤150 x10⁹ cells/L in each combination for 2 predictors modeling were correlated with death.

Conclusions

We report key predictors of mortality in pediatric patients with clinical diphtheria. The presence of these features when admitted to the hospital must be taken into account, because they can lead to fatal outcome.

Whole Genome Sequencing for Surveillance of Diphtheria in Low Incidence Settings

Corynebacterium diphtheriae (C. diphtheriae) is a relatively rare pathogen in most Western countries. While toxin producing strains can cause pharyngeal diphtheria with potentially fatal outcomes, the more common presentation is wound infections. The diphtheria toxin is encoded on a prophage and can also be carried by Corynebacterium ulcerans and Corynebacterium pseudotuberculosis. Currently, across Europe, infections are mainly diagnosed in travelers and refugees from regions where diphtheria is more endemic, patients from urban areas with poor hygiene, and intravenous drug users. About half of the cases are non-toxin producing isolates. Rapid identification of the bacterial pathogen and toxin production is a critical element of patient and outbreak management. Beside the immediate clinical management of the patient, public health agencies should be informed of toxigenic C. diphtheriae diagnoses as soon as possible. The collection of case-related epidemiological data from the patient is often challenging due to language barriers and social circumstances. However, information on patient contacts, vaccine status and travel/refugee route, where appropriate, is critical, and should be documented. In addition, isolates should be characterized using high resolution typing, in order to identify transmissions and outbreaks. In recent years, whole genome sequencing (WGS) has become the gold standard of high-resolution typing methods, allowing detailed investigations of pathogen transmissions. De-centralized sequencing strategies with redundancy in sequencing capacities, followed by data exchange may be a valuable future option, especially since WGS becomes more available and portable. In this context, the sharing of sequence data, using public available platforms, is essential. A close interaction between microbiology laboratories, treating physicians, refugee centers, social workers, and public health officials is a key element in successful management of suspected outbreaks. Analyzing bacterial isolates at reference centers may further help to provide more specialized microbiological techniques and to standardize information, but this is also more time consuming during an outbreak. Centralized communication strategies between public health agencies and laboratories helps considerably in establishing and coordinating effective surveillance and infection control. We review the current literature on high-resolution typing of C. diphtheriae and share our own experience with the coordination of a Swiss-German outbreak.

Proteomics of diphtheria toxoid vaccines reveals multiple proteins that are immunogenic and may contribute to protection of humans against Corynebacterium diphtheriae

Introduced for mass immunization in the 1920s, vaccines against diphtheria are among the oldest and safest vaccines known. The basic principle of their production is the inactivation of purified diphtheria toxin by formaldehyde cross-linking, which converts the potentially fatal toxin in a completely harmless protein aggregate, which is still immunogenic. Since in addition to diphtheria toxin also other proteins may be secreted by Corynebacterium diphtheriae during cultivation, we assumed that diphtheria toxoid might not be the only component present in the vaccine. To address this question, we established a protocol to reverse formaldehyde cross-linking and carried out mass spectrometric analyses. Different secreted, membrane-associated and cytoplasmic proteins of C. diphtheriae were detected in several vaccine preparations from across the world. Based on these results, bioinformatics and Western blot analyses were applied to characterize if these proteins are immunogenic and may therefore support protection against C. diphtheriae. In frame of this study, we could show that the C. diphtheriae toxoid vaccines induce antibodies against different C. diphtheriae proteins and against diphtheria toxin secreted by Corynebacterium ulcerans, an emerging pathogen which is outnumbering C. diphtheriae as cause of diphtheria-like illness in Western Europe.

Development of nanoparticle adjuvants to potentiate the immune response against diphtheria toxoid

BACKGROUND

Over the years, diphtheria was known as contagious fatal infection caused by Corynebacterium diphtheria that affects upper respiratory system. The spread of diphtheria epidemic disease is best prevented by vaccination with diphtheria toxoid vaccine. Aluminum adjuvants were reported to stimulate the immune responses to killed and subunit vaccines.

OBJECTIVE

Our study aimed to minimize adjuvant particles size, to gain insight of resulting immunity titer and impact on immune response antibody subtypes.

METHODS

Aluminum salts and calcium phosphate adjuvants were prepared, followed by micro/nanoparticle adjuvants preparation. After formulation of diphtheria vaccine from diphtheria toxoid and developed adjuvants, we evaluated efficacy of these prepared vaccines based on their impact on immune response via measuring antibodies titer, antibodies isotyping and cytokines profile in immunized mice.

RESULTS

A noteworthy increase in immunological parameters was observed; antibodies titer was higher in serum of mice injected with nanoparticle adjuvants-containing vaccine than mice injected with standard adjuvant-containing vaccine and commercial vaccine. Aluminum compounds adjuvants (nanoparticles and microparticles formulation) and microparticles calcium phosphate adjuvant induce TH2 response, while nanoparticles calcium phosphate and microparticles aluminum compounds adjuvants stimulate TH1 response.

CONCLUSIONS

Different treatments to our adjuvant preparations (nanoparticles and microparticles formulation) had a considerable impact on vaccine immunogenicity.

Prospective Study of Diphtheria for Neurological Complications

Aim

To study the spectrum of neurological complications of diphtheria, timing of onset with respect to respiratory disease, and pattern of recovery.

Settings and Design

Prospective, observational, hospital-based study conducted in tertiary care hospital.

Materials and Methods

Twenty-eight cases of diphtheria with neurological complications were admitted during the period of study. Demographic profile, age, gender, status of immunization, past history stressing on the severity of the respiratory disease, and complaints regarding diverse complications of diphtheria were recorded. Detailed clinical and central nervous system examinations along with relevant investigations were carried out.

Results

Children were in the age group of 3-18 years. All 28 children presented with bulbar symptoms. Isolated palatal palsy was present in 18 children (64%). Third cranial involvement was present in four children. Three children had unilateral lower motor neuron facial palsy and one child had sixth cranial nerve palsy. Nine children developed symmetric limb weakness. Diaphragmatic palsy was present in three children with the onset from 1-3 weeks after pharyngeal diphtheria. Loss of vasomotor tone was present in two children. Recovery was complete in all 28 children.

Conclusion

Pediatricians/neurophysicians should have a high index of suspicion to recognize diphtheritic polyneuropathy. It carries good prognosis, hence timely diagnosis and differentiation from other neuropathies is a prerequisite for rational management and contact tracing.

Corynebacterium species nasopharyngeal carriage in asymptomatic individuals aged ≥ 65 years in Germany

PURPOSE

The prevalence of protective anti-diphtheria toxin antibodies decreases with age. Therefore, the elderly might serve as reservoir for potentially toxigenic Corynebacterium (C.) species (C. diphtheriae, C. ulcerans, and C. pseudotuberculosis). This study aimed to examine the colonization rate of the nasopharynx with corynebacteria of individuals aged 65 years and older.

METHODS

In the period from October 2012 to June 2013, nasal and throat swabs were taken from 714 asymptomatic subjects aged 65-106 years (average age 77.2) at three regions in Germany and investigated for Corynebacterium species.

RESULTS

A total of 402 strains of Corynebacterium species were isolated from 388 out of 714 asymptomatic subjects (carriage rate 54.3%). The carriage rate was significantly higher in study participants living in retirement homes (68.4%) compared to those living autonomously at home (51.1%). Strains were isolated mostly from the nose (99%). Corynebacterium accolens was the most often isolated species (39.8%), followed by C. propinquum (24.1%), C. pseudodiphtheriticum (19.4%), and C. tuberculostearicum (10.2%). No C. diphtheriae, C. ulcerans, and C. pseudotuberculosis strains were isolated. A subsample of 74 subjects was tested serologically for anti-diphtheria antibodies. Protective anti-diphtheria toxin antibodies were found in 29.7% of the subjects; 70.3% showed no protective immunity.

CONCLUSIONS

These results suggest that carriage of potentially toxigenic corynebacteria is very rare among people aged 65 and older in Germany. However, the low prevalence of protective anti-diphtheria toxin antibodies might pose a risk for acquiring diphtheria especially for the elderly.

The Hsp90 machinery facilitates the transport of diphtheria toxin into human cells

Diphtheria toxin kills human cells because it delivers its enzyme domain DTA into their cytosol where it inhibits protein synthesis. After receptor-mediated uptake of the toxin, DTA translocates from acidic endosomes into the cytosol, which might be assisted by host cell factors. Here we investigated the role of Hsp90 and its co-chaperones during the uptake of native diphtheria toxin into human cells and identified the components of the Hsp90 machinery including Hsp90, Hsp70, Cyp40 and the FK506 binding proteins FKBP51 and FKBP52 as DTA binding partners. Moreover, pharmacological inhibition of the chaperone activity of Hsp90 and Hsp70 and of the peptidyl-prolyl cis/trans isomerase (PPIase) activity of Cyps and FKBPs protected cells from intoxication with diphtheria toxin and inhibited the pH-dependent trans-membrane transport of DTA into the cytosol. In conclusion, these host cell factors facilitate toxin uptake into human cells, which might lead to development of novel therapeutic strategies against diphtheria.

Diphtheria outbreak in Lao People's Democratic Republic, 2012-2013

BACKGROUND

Diphtheria is a vaccine-preventable disease. When vaccination coverage and population immunity are low, outbreaks can occur. We investigated a diphtheria outbreak in Lao People's Democratic Republic that occurred during 2012-2013 and highlighted challenges in immunization services delivery to children in the country.

METHODS

We reviewed diphtheria surveillance data from April 1, 2012-May 31, 2013. A diphtheria case was defined as a respiratory illness consisting of pharyngitis, tonsillitis, or laryngitis, and an adherent tonsillar or nasopharyngeal pseudomembrane. To identify potential risk factors for diphtheria, we conducted a retrospective case-control study with two aged-matched neighborhood controls per case-patient in Houaphan Province, using bivariate analysis to calculate matched odds ratio (mOR) with 95% confidence intervals (CI). Reasons for non-vaccination among unvaccinated persons were assessed.

RESULTS

Sixty-two clinical cases of diphtheria and 12 diphtheria-related deaths were reported in seven of 17 provinces. Among case-patients, 43 (69%) were <15years old, five (8%) reported receiving three DTP doses (DTP3), 21 (34%) had received no DTP doses, and 35 (56%) had unknown vaccination status. For the case-control study, 42 of 52 diphtheria case-patients from Houaphan province and 79 matched-controls were enrolled. Five (12%) case-patients and 20 (25%) controls had received DTP3 (mOR=0.4, CI=0.1-1.7). No diphtheria toxoid-containing vaccine was received by 20 (48%) case-patients and 38 (46%) controls. Among case-patients and controls with no DTP dose, 43% of case-patients and 40% of controls lacked access to routine immunization services.

CONCLUSION

Suboptimal DTP3 coverage likely caused the outbreak. To prevent continued outbreaks, access to routine immunization services should be strengthened, outreach visits need to be increased, and missed opportunities need to be minimized. In the short term, to rapidly increase population immunity, three rounds of DTP immunization campaign should be completed, targeting children aged 0-14years in affected provinces.

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.

Immunogenicity and safety of the new reduced-dose tetanus-diphtheria vaccine in healthy Korean adolescents: A comparative active control, double-blind, randomized, multicenter phase III study

BACKGROUND/PURPOSE

A new reduced-dose tetanus-diphtheria (Td) vaccine was developed in Korea, and phase I and II clinical trials were successfully undertaken. We conducted this double-blind, randomized, multicenter phase III clinical trial to assess the immunogenicity and safety of the new Td vaccine.

METHODS

Healthy adolescents 11-12 years of age were enrolled and randomized to receive the new Td vaccine (study group) or a commercially available Td vaccine (control group). Blood samples were collected prior to and 4 weeks after the vaccination. Between the study and control groups, seroprotection rate, booster response, and geometric mean titer of antibodies against diphtheria and tetanus toxoids were compared after the vaccination. All solicited and unsolicited adverse events and serious adverse events during the 6-week study period were monitored.

RESULTS

A total of 164 adolescents received vaccination, and 156 of them were evaluated to assess immunogenicity. The seroprotection rate and geometric mean titer for antibodies against diphtheria were significantly higher in the study group, whereas those against tetanus were significantly higher in the control group. However, all seroprotection rates against diphtheria and tetanus in the study and control groups were high: 100% against diphtheria and tetanus in the study group, and 98.7% against diphtheria and 100% against tetanus in the control group. No significant differences in the frequency of solicited and unsolicited adverse events were observed between the two vaccine groups.

CONCLUSION

The new Td vaccine is highly immunogenic and safe, and this new Td vaccine can be effectively used for preventing diphtheria and tetanus.

Determination of the presence of diphtheria toxin in the myocardial tissue of rabbits and a female subject by using an immunofluorescent antibody method

BACKGROUND

Clinical diagnosis of diphtheria is often difficult, in particular in countries where the disease is rarely observed, such as Turkey. In 2011, after 12 years of no recorded diphtheria cases in Turkey, a 34-year-old woman was diagnosed with diphtheria; she later died of myocarditis. In this study, we aimed to demonstrate the diagnostic potential of an immunofluorescent antibody method to determine the presence of diphtheria toxin (DT) in the myocardial cells of DT-injected rabbits and the female subject.

METHODS

We randomly divided rabbits into two groups: a control group and a DT-injected group. Diphtheria intoxication was simulated in the rabbits by intravenous injection of DT. The myocardium of the rabbits and the female subject were harvested for histopathologic and immunofluorescence examination. A mouse monoclonal anti-DT antibody was used for the immunofluorescent antibody method.

RESULTS

The presence of DT in the myocardial cells of both the rabbits and the female subject was visualized using the immunofluorescent method.

CONCLUSIONS

Laboratory diagnosis of diphtheria is challenging because of non-toxigenic C. diphtheriae strains and/or the dysfunction of DT. However, visualizing the presence of DT in the myocardial tissue may act as an indicator of biologically active DT. We validated that an immunofluorescent method, which utilizes a monoclonal anti-DT (A-subunit specific) antibody, is a useful diagnostic tool to determine the presence of DT in the myocardium of rabbits and human.

The role of CRISPR-Cas systems in virulence of pathogenic bacteria

Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) genes are present in many bacterial and archaeal genomes. Since the discovery of the typical CRISPR loci in the 1980s, well before their physiological role was revealed, their variable sequences have been used as a complementary typing tool in diagnostic, epidemiologic, and evolutionary analyses of prokaryotic strains. The discovery that CRISPR spacers are often identical to sequence fragments of mobile genetic elements was a major breakthrough that eventually led to the elucidation of CRISPR-Cas as an adaptive immunity system. Key elements of this unique prokaryotic defense system are small CRISPR RNAs that guide nucleases to complementary target nucleic acids of invading viruses and plasmids, generally followed by the degradation of the invader. In addition, several recent studies have pointed at direct links of CRISPR-Cas to regulation of a range of stress-related phenomena. An interesting example concerns a pathogenic bacterium that possesses a CRISPR-associated ribonucleoprotein complex that may play a dual role in defense and/or virulence. In this review, we describe recently reported cases of potential involvement of CRISPR-Cas systems in bacterial stress responses in general and bacterial virulence in particular.

Diphtheria - 'The strangling angel' of children

Diphtheria, an acute infectious condition caused by Corynebacterium diphtheriae, was once a major killer of children. Although the mortality rates dropped dramatically in the mid-twentieth century, due to a combination of improved standards of living and immunization programs, outbreaks are still occurring. Two children, aged four and five years respectively, are reported to demonstrate characteristic features of lethal cases. Death in case 1 was due to an extensive upper airway pseudomembrane causing acute respiratory failure. The diagnosis of diphtheria was only made at postmortem. Death in case 2 was due to acute cardiac failure with heart block complicating diphtheria. Other mechanisms in fatal cases involve disseminated intravascular coagulation, renal and endocrine failure. Declining levels of immunity among adults has resulted in a change in the epidemiological pattern of the disease with an older age of victims in recent outbreaks. As a result of population shifts and failure to immunize children it is likely that forensic pathologists may see more cases of diphtheria in the future. Due to the rarity of cases in Western communities and atypical presentations, the diagnosis may only be established at autopsy.

Diphtheria Re-emergence: Problems Faced by Developing Countries

In the pre-vaccination era, diphtheria was a leading cause of childhood mortality. With the introduction of routine childhood immunization, paediatric care and improved hygiene status the disease has been almost completely eradicated in many developed countries. On the contrary developing countries, still account for 80-90% of the global burden. Retrospective analysis of 52 cases of diphtheria over a period of 12 years at a tertiary referral hospital was carried out. They were analyzed for mortality and morbidity trends, immunization status, microbiological confirmation rates and antidiphtheritic serum (ADS) administration. Incidence in those over 5 years was 59.61%. Only 11.54% cases were either partially or fully immunized. The case fatality rate was 36.53%. Culture was performed only in 17 cases whereas ADS was administered in only 16 cases. In conclusion, the occurrence of diphtheria even in those immunized highlights the flaws in the present immunization program. Poor immunization coverage, lack of ADS, antibiotic resistance are the main reasons for re-emergence of diphtheria.

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, tetanus, and pertussis immunity in Indian adults and immunogenicity of td vaccine

Rise of diphtheria cases in adults is a cause of concern worldwide. Pertussis is also now affecting adults. We assessed serum levels of tetanus, diphtheria and pertussis antibodies in 62 adults in Pune, India, who had missed their primary immunization. All adults were then given three doses of tetanus-diphtheria (Td) vaccine at 0, 1, and 6 months. All adults were immune to tetanus but 78% had long-term protection. For diphtheria, 88% were protected but only 9% had long term immunity. Only 60% were immune to pertussis. After three doses of the vaccine, long term immunity to both tetanus and diphtheria increased to 87% and 97%, respectively (P < 0.05). Geometric mean titres (GMT) of both antibodies also increased significantly. The vaccine caused minor local reactions and mild fever in a few subjects. There is need of three doses of Td vaccination in those Indian adults, who missed their primary immunization. Susceptibility to pertussis also needs to be further explored.

Spezifische Infektionen

Die Tuberkulose ist die weltweit häufigste infektionsbedingte Todesursache und führt nur selten zur Aufnahme auf der Intensivstation. Hauptgründe für eine Intensivtherapie sind eine respiratorische Insuffizienz, Thoraxeingriffe, fortgeschrittene Tbc-Meningitis, tuberkulöse Perikarditis, Nebenwirkungen von Tuberkulostatika und eine tuberkuloseassoziierte Addison-Krise [11].

Corynebacterium diphtheriae: identification and characterization of a channel-forming protein in the cell wall

The cell wall fraction of the gram-positive, nontoxic Corynebacterium diphtheriae strain C8r(-) Tox- (=ATCC 11913) contained a channel-forming protein, as judged from reconstitution experiments with artificial lipid bilayer experiments. The channel-forming protein was present in detergent-treated cell walls and in extracts of whole cells obtained using organic solvents. The protein had an apparent molecular mass of about 66 kDa as determined on Tricine-containing sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels and consisted of subunits having a molecular mass of about 5 kDa. Single-channel experiments with the purified protein suggested that the protein formed channels with a single-channel conductance of 2.25 nS in 1 M KCl. Further single-channel analysis suggested that the cell wall channel is wide and water filled because it has only slight selectivity for cations over anions and its conductance followed the mobility sequence of cations and anions in the aqueous phase. Antibodies raised against PorA, the subunit of the cell wall channel of Corynebacterium glutamicum, detected both monomers and oligomers of the isolated protein, suggesting that there are highly conserved epitopes in the cell wall channels of C. diphtheriae and PorA. Localization of the protein on the cell surface was confirmed by an enzyme-linked immunosorbent assay. The prospective homology of PorA with the cell wall channel of C. diphtheriae was used to identify the cell wall channel gene, cdporA, in the known genome of C. diphtheriae. The gene and its flanking regions were cloned and sequenced. CdporA is a protein that is 43 amino acids long and does not have a leader sequence. cdporA was expressed in a C. glutamicum strain that lacked the major outer membrane channels PorA and PorH. Organic solvent extracts of the transformed cells formed in lipid bilayer membranes the same channels as the purified CdporA protein of C. diphtheriae formed, suggesting that the expressed protein is able to complement the PorA and PorH deficiency of the C. glutamicum strain. The study is the first report of a cell wall channel in a pathogenic Corynebacterium strain.

Travel Recommendations for Older Adults

Older age is an important factor in preparing travelers owing not only to physiologic changes and the increased probability of underlying medical conditions and prescription medications but also to immune status with regard to naturally acquired immunity versus immunization for vaccine-preventable diseases. Cardiovascular events (including myocardial infarctions and cerebrovascular accidents) account for most deaths abroad, followed by injuries. To plan for healthy travel, international travelers should be advised to seek care at least 4 to 6 weeks before departure. Travel medicine is a dynamic field because conditions worldwide are subject to rapid change. Clinicians must maintain a current base of knowledge if they will be regularly advising travelers or must set a threshold for referral to a travel medicine specialist.

Diphtheria

Diphtheria is a contagious upper respiratory illness that was a major cause of childhood mortality in the prevaccine era. In the early twentieth century, an effective toxoid vaccine was developed. Implementation of childhood vaccination virtually eliminated diphtheria from developed countries after the Second World War and implementation of the Expanded Program on Immunization in developing countries led to rapid declines in diphtheria globally in the 1980s. However, in the 1990s, a massive epidemic of diphtheria spread throughout the countries of the former Soviet Union. Unlike the prevaccine era, most cases of severe disease and deaths were reported among adults. Multiple factors contributed to the epidemic, including increased susceptibility among both adults and children; suboptimal socioeconomic conditions; high population movement; and delay in implementing appropriate control measures. Mass immunization was the key element in the epidemic control strategy developed and implemented in a well-coordinated response by an international public health coalition. This strategy focused on rapidly raising population immunity of both adults and children; the immunization of more than 140,000,000 adults and adolescents and millions of children successfully controlled the epidemic. While improved coverage of children in developing countries with diphtheria toxoid has led to progressive decreases in diphtheria; eradication is unlikely in the foreseeable future and gaps in immunity among adult population exist or are developing in many other countries. Routine childhood immunization with diphtheria toxoid is the key to controlling diphtheria while the role of routine adult reimmunization is less established; mass immunization will remain an important control measure for widespread diphtheria outbreaks.

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.

[Immunity to diphtheria among adults older than 65 years]

BACKGROUND AND OBJECTIVE

To know the immune state against diphtheria through a survey, a consultation of the vaccination documents and a seroepidemiologic study of an old population.

PATIENTS AND METHOD

The immunization status and the prevalence of antidiphtheria antibodies were determined in a representative sample (n = 231) of this population group (> 65 years). Concentrations of toxin antibodies were measured using a commercial ELISA kit. Samples with titres > 0.1 UI/ml were considered protective.

RESULTS

In the vaccination documents we only found 19 old individuals vaccinated against tetanus-diphtheria. 47.1% had no protective titres. Geometric mean titres were 0.12 UI/ml. There was no statistically significant difference between the variables age and sex and the prevalence of antibodies. 84.4% of the 122 seropositives did not report having received diphtheria vaccine and neither had documents about the vaccination.

CONCLUSION

There were almost no documents about diphtheria vaccination. Therefore, the serologic study is the only reliable way to know the immunity status against diphtheria in elderly people. Approximately 50% of this population need primary immunization. The rest of this group need to have completed antidiphtheria vaccination or a dose booster within a period of 2 years in order to guarantee protective antibody levels against diphtheria.

Immunity to diphtheria among refugees in southern Italy

This study assessed the immune status against diphtheria of a sample of refugees (mainly Kosovars and Kurds) in southern Italy (Puglia). The 54.8% of 1128 subjects showed full protection against diphtheria, 30.1% had basic protection and 15.1% resulted seronegative for antitoxin antibody. Only from 45.9 to 73.9% of 0-10 years old refugees were fully protected while from 12.3 to 24.2% were seronegative to diphtheria with the poorest protection rate among Kurdish children from Turkey. Kosovars showed the highest protection rate to diphtheria whereas data suggest a probable endemic level of diphtheria in Iraq. The screening of refugees revealed a low coverage rate for diphtheria, especially in children, probably due to deterioration of the health service infrastructure or intermittent basic health care in the country of provenience. In terms of public health measures, there is the need of administering booster doses to all refugees coming into Italy and into other host countries to increase the coverage rate against diphtheria. The implementation of the immunization programs against diphtheria in the countries of provenience is also strongly recommended.

Facilitating the WHO expanded program of immunization: the clinical profile of a combined diphtheria, tetanus, pertussis, hepatitis B and Haemophilus influenzae type b vaccine

BACKGROUND

Vaccines are important weapons in the fight against infectious diseases. The World Health Organization (WHO) Expanded Program on Immunization (EPI) has been extended to include recommendations for hepatitis B and Haemophilus influenzae type b (Hib) vaccinations. The WHO has recommended that combined vaccines be used where possible, to reduce the logistic costs of vaccine delivery. This paper reviews the efficacy, safety and cost-effectiveness of Tritanrix-HB/Hib, the only commercially available combined diphtheria, tetanus, whole cell pertussis, hepatitis B and conjugated Hib vaccine.

METHODS

The immunogenicity and reactogenicity results of five published clinical trials involving Tritanrix-HB/Hib in a variety of immunization schedules and countries were reviewed. Based on these data and cost-effectiveness studies, an assessment of its suitability for use in national immunization programs was made.

RESULTS

Tritanrix-HB/Hib has shown excellent immunogenicity in clinical trials using a variety of schedules, with no reduced immunogenicity observed for any of the components of the combined vaccine. It has similar reactogenicity to DTPw vaccines alone. Pharmacoeconomic analyses have shown combined DTP-HB/Hib vaccines to be cost-effective compared to separate vaccines.

CONCLUSIONS

Replacement of DTPw vaccination by Tritanrix-HB/Hib can be done without modifying the existing national immunization programs. This should facilitate widespread coverage of hepatitis B and Hib vaccinations and their rapid incorporation into the EPI.

The global impact of vaccines containing aluminium adjuvants

Immunization against childhood vaccine-preventable diseases has arguably had the greatest impact on the health of children of any public health intervention. Many of the vaccines used in the Expanded Programme on Immunization (EPI) have contained aluminium-based adjuvants. As such, these adjuvants have played a vital role in enabling the basic vaccines to be used effectively. DTP global supply is fragile and could easily be upset through the loss of even one major vaccine manufacturer. Non-aluminium adjuvants could not readily replace aluminium adjuvants. New generation vaccines will probably need new generation adjuvants. The impact of vaccines with adjuvants is discussed. Having provided decades of reliable, safe service in their relatively simple chemical formulations, adjuvants are likely to be with us, in one form or another, for the indefinite future.

Infection of the skin caused by Corynebacterium ulcerans and mimicking classical cutaneous diphtheria

Extrapharyngeal infections caused by Corynebacterium ulcerans have rarely been reported previously, and diphtheria toxin production has usually not been addressed. This case demonstrates that strains of C. ulcerans that produce diphtheria toxin can cause infections of the skin that completely mimic typical cutaneous diphtheria, thereby potentially providing a source of bacteria capable of causing life-threatening diseases in the patient's environment. Therefore, it is recommended to screen wound swabs for coryneform bacteria, identify all isolates, carefully assess possible toxin production, and send questionable strains to a specialist or a reference laboratory.

Fifth vaccination with dipthteria, tetanus and acellular pertussis is beneficial in four- to six-year-olds

OBJECTIVE

Diphtheria, tetanus and pertussis serum antibody titers were assessed before a fifth dose of diphtheria-tetanus-acellular pertussis (DTaP) or diphtheria-tetanus-whole cell pertussis (DTwP) vaccination at age 4 to 6 years.

METHODS

Healthy children who had participated in a series of National Institutes of Health-sponsored trials assessing DTwP and DTaP vaccines provided prevaccination sera before a fifth dose of DTwP or DTaP. The trial design was prospective, randomized and double blind. Diphtheria, tetanus and pertussis antibody titers were measured by enzyme-linked immunosorbent assay. Pertussis results are expressed in enzyme-linked immunosorbent assay units/ml based on US Food and Drug Administration reference sera. Tetanus and diphtheria toxin concentrations are expressed in IU/ml with a WHO international reference sera as a standard.

RESULTS

For diphtheria 100% of the children had antibody titers above the minimum protective level of 0.01 IU/ml and 86 to 100% (depending on prior vaccine product) had titers >0.1 IU/ml. However, only 0 to 40% of the children had antibody titers > or =1.0 IU/ml, a titer associated with more certain durable protection. For tetanus none of the children had an antibody titer below 0.01 IU/ml, and 93 to 100% had titers > or =0.1 IU/ml, a titer associated with more certain, durable protection. For pertussis the geometric mean concentrations of antibody before booster were uniformly very low, and the percentage of children exceeding the minimum detectable titer of antibody by 4-fold was also low.

CONCLUSION

Before a 4- to 6-year-old booster, a large proportion of children have titers of antibody to diphtheria below the certain, durable protective level. Because serologic correlates and minimum protective titers of antibody to pertussis antigens have not been established, the relevance of the low titers determined in the current study is unknown but a potential concern.

Use of amplified fragment length polymorphisms for typing Corynebacterium diphtheriae

Amplified fragment length polymorphism (AFLP) was investigated for the differentiation of Corynebacterium diphtheriae isolates. Analysis using Taxotron revealed 10 distinct AFLP profiles among 57 isolates. Strains with ribotype patterns D1, D4, and D12 could not be distinguished; however, the technique discriminated isolates of ribotype patterns D3, D6, and D7 further. AFLP was rapid, fairly inexpensive, and reproducible and could be used as an alternative to ribotyping.

Immunity to diphtheria and tetanus in England and Wales

The immunity profile of the English and Welsh population to diphtheria and tetanus has been determined by measuring diphtheria and tetanus antitoxin levels for 3088 and 3142 sera, respectively. Time-resolved fluorimetric immunoassay - DELFIA was used to measure diphtheria antitoxin levels and an in-house, indirect ELISA to measure tetanus antitoxin levels. More than 80% of those aged between 2 and 20-24 years had protective diphtheria antitoxin levels of 0.01 IU/ml, or greater, and more than 80% of those aged between 4 and 35-39 years had protective tetanus antitoxin levels of 0.1 IU/ml, or greater. Only 29% and 53% of those aged 60 and over were protected against diphtheria and tetanus. Two increases of diphtheria antitoxin levels greater than 0.1 IU/ml and tetanus antitoxin levels greater than 1.0 IU/ml were apparent, starting at 4 and 14 years of age, which correspond with the policy of giving a diphtheria and tetanus toxoid booster on school entry and a tetanus plus low-dose diphtheria toxoid (recently introduced) booster to school leavers. This is the first comprehensive study of diphtheria and tetanus immunity in the English and Welsh population and shows that the accelerated schedule of immunisation, introduced in 1990, has effectively primed immunological memory against both these antigens and that boosting at school entry and at school leaving is effective in increasing levels of immunity.

The changing epidemiology of diphtheria in the vaccine era

The epidemic of diphtheria in the Newly Independent States (NIS) of the former Soviet Union has drawn attention to our incomplete understanding of the epidemiology of diphtheria. Many unanswered questions remain concerning the reasons for a resurgence of diphtheria and for the shift in the age of patients and concerning the mechanisms for acquisition of immunity in adults through natural infection under unfavorable living conditions. Other unanswered questions relate to the precise role of socioeconomic factors and hygiene conditions in the initiation, buildup, and spread of the epidemic. Important characteristics of the NIS epidemic can be used to help predict the spread of future diphtheria epidemics. These characteristics include a high proportion of infected adults, a progressive spread of disease from urban centers to rural areas, and transition from initial amplification of disease in groups with high rates of close contacts in focalized, well-distinguished outbreaks to a more generalized epidemic.

Evaluation of a single dose of diphtheria-tetanus toxoids among adults in Odessa, Ukraine, 1995: immunogenicity and adverse reactions

Epidemic diphtheria spread to Ukraine in 1991, where it peaked in 1995 with >5,000 reported cases. To refine epidemic control strategies, immunogenicity of a tetanus-diphtheria toxoids vaccine (Td) containing 2 limits of flocculation (Lf) diphtheria toxoid was evaluated. During a mass vaccination campaign, adults at a clinic in Odessa received one dose of Td. At enrollment, 57.2% of 341 study participants had levels of diphtheria antitoxin (DAT) >/=0.1 IU/mL. Thirty and 180 days after receiving one dose of Td, 91.5% and 84.5% of the participants, respectively, had DAT levels >/=0.1 IU/mL. However, among 40- to 49-year-old participants, only 78.8% and 73.8% had DAT levels >/=0.1 IU/mL at 30 and 180 days, respectively. This study suggests that one dose of 2 Lf diphtheria toxoid is highly effective in raising DAT to protective levels in most adults; however, the study also shows that certain age groups, particularly persons 40-49 and, to a lesser degree, 30-39 years old may require additional doses or a complete three-dose primary vaccination series for optimal protection against diphtheria.

Immune response to diphtheria booster vaccine in the Baltic states

A study was done to measure baseline levels of immunity to diphtheria and antibody responses to different doses of diphtheria vaccine in study participants in the three Baltic states. Diphtheria booster vaccines containing either 3 (Estonia and Lithuania), 6 (Latvia), or 12 (Latvia) limit of flocculation units of diphtheria toxoid were administered to 2315 adults. Diphtheria antibody levels were tested before and 1-2 months after vaccination. Before vaccination, 40% of the participants in Estonia, 32% in Lithuania, and 38% in Latvia had antibody levels <0.01 IU/mL, the level for minimum protection. After vaccination, 79% of the participants in Estonia, 83% in Lithuania, and 81% in Latvia had antibody levels >0. 1 IU/mL, the minimum level for full protection. However, in each of the countries, about one-third of the 40- to 49-year-old participants would have benefited from additional doses of vaccine. There was not a significantly different antibody response among persons receiving the three different doses. Age and the level of prevaccination immunity had a modifying effect on the response to vaccination; however, sex did not.

Successful control of epidemic diphtheria in the states of the Former Union of Soviet Socialist Republics: lessons learned

Epidemic diphtheria reemerged in the Russian Federation in 1990 and spread to all Newly Independent States (NIS) and Baltic States by the end of 1994. Factors contributing to the epidemic included increased susceptibility of both children and adults, socioeconomic instability, population movement, deteriorating health infrastructure, initial shortages of vaccine, and delays in implementing control measures. In 1995, aggressive control strategies were implemented, and since then, all affected countries have reported decreases of diphtheria; however, continued efforts by national health authorities and international assistance are still needed. The legacy of this epidemic includes a reexamination of the global diphtheria control strategy, new laboratory techniques for diphtheria diagnosis and analysis, and a model for future public health emergencies in the successful collaboration of multiple international partners. The reemergence of diphtheria warns of an immediate threat of other epidemics in the NIS and Baltic States and a longer-term potential for the reemergence of vaccine-preventable diseases elsewhere. Continued investment in improved vaccines, control strategies, training, and laboratory techniques is needed.

Epidemiology and control of diphtheria in the Republic of Moldova, 1946-1996

In 1994-1996, the Republic of Moldova was stricken with an epidemic of diphtheria after >30 years of routine diphtheria immunization and the near absence of the disease for nearly 20 years. The intensity of the epidemic gradually grew, reaching a peak in 1994-1995. The epidemiology of diphtheria in Moldova during this period is described along with laboratory findings and control measures. Pharyngeal diphtheria was the predominant clinical form of the disease (97% of cases), and it most often developed in a localized form (70%), with 20% in the toxic form. The clinical diagnosis of diphtheria was bacteriologically confirmed in 91% of cases: Of the cases tested for biotype, 91.3% were gravis, 8.5% were mitis, and 0. 2% were intermedius. Of 494 toxigenic isolates from cases and carriers at the beginning of the epidemic, 47% were nonphagotypeable strains, and 25.7% were phagotype VI strains. Aggressive population-based diphtheria control measures, a mass immunization campaign, rapid case identification, antibiotic prophylaxis and supplemental immunization of close contacts in clusters of infection, and high coverage with routine immunization rapidly controlled the epidemic within Moldova.

Immunogenicity of tetanus-diphtheria toxoids (Td) among Ukrainian adults: implications for diphtheria control in the Newly Independent States of the Former Soviet Union

After 30 years of control, epidemic diphtheria returned to the Soviet Union in 1990. To develop control strategies, the immunogenicity of the tetanus and diphtheria toxoids (Td) vaccine was assessed. Workers who were 18-67 years old received two Td immunizations separated by 30 days. A neutralization assay determined diphtheria antitoxin (DAT) on enrollment and on days 7, 30, 60, and 425. On enrollment, 43.0% of 488 workers had DAT <0.1 IU/mL. After one dose, 88.5% had DAT >/=0.1 IU/mL, after two doses, 92.2% had >/=0.1 IU/mL and >90% of participants <30 or >/=50 years of age attained >/=1.0 IU/mL; however, only 78.4% of those who were 30-39 years old and 51.8% of those who were 40-49 years old achieved >/=1.0 IU/mL after two doses. To control the epidemic in Ukraine, one Td dose should be administered to virtually the entire population (persons 30-49 years old require three doses of Td for optimal individual protection and to maximize population immunity).