Diphtheria surveillance and control in the Former Soviet Union and the Newly Independent States

Improved coverage and timing of childhood vaccinations in two post-Soviet countries, Armenia and Kyrgyzstan

BACKGROUND

Timing of childhood vaccinations has received close attention in many countries. Little is known about the trends in correctly timed vaccination in former Soviet countries. We examined trends in vaccination coverage and correct timing of vaccination in two post-Soviet countries, Armenia and Kyrgyzstan, and analyzed factors associated with delayed vaccinations.

METHODS

We used data from the Demographic and Health Surveys; the surveys were conducted in 2000 (n = 1726), 2005 (n = 1430) and 2010 (n = 1473) in Armenia and in 1997 (n = 1127) and 2012 (n = 4363) in Kyrgyzstan. We applied the Kaplan-Meier method to estimate age-specific vaccination coverage with diphtheria, tetanus and pertussis (DTP) vaccine and a measles-containing vaccine (MCV). A Cox proportional hazard regression with shared frailty was used to examine factors associated with delayed vaccinations.

RESULTS

Vaccination coverage for all three doses of the DTP vaccine increased in Armenia from 92 % in 2000 to 96 % in 2010. In Kyrgyzstan, DTP coverage was 96 % and 97 % in 1997 and 2012, respectively. Vaccination coverage for MCV increased from 89 % (Armenia, 2000) and 93 % (Kyrgyzstan, 1997) to 97 % (Armenia, 2010) and 98 % (Kyrgyzstan, 2012). The proportion of children with correctly timed vaccinations increased over time for all examined vaccinations in both countries. For example, the proportion of children in Armenia with correctly timed first DTP dose (DTP1) increased from 46 % (2000) to 66 % (2010). In Kyrgyzstan, the proportion of correctly timed DTP1 increased from 75 % (1997) to 87 % (2012). In Armenia, delays in the third DTP dose (DTP3) and MCV vaccinations were less likely to occur in the capital, whereas in Kyrgyzstan DTP3 and MCV start was delayed in the capital compared to other regions of the country. Also, in Armenia living in urban areas was associated with delayed vaccinations.

CONCLUSIONS

Vaccination coverage and timing of vaccination improved over the last years in both countries. Further efforts are needed to reduce regional differences in timely vaccinations.

Attitudes and knowledge of Georgian physicians regarding cervical cancer prevention, 2010

OBJECTIVE

To document Georgian physician's knowledge, attitudes, and practices concerning HPV, Pap smear testing, and HPV vaccination, and to assess whether physician practice might change with additional education and training.

METHODS

A cross-sectional study was conducted using a self-administered written survey of 288 physicians practicing in 7 healthcare institutions in Tbilisi, Rustavi, and Batumi, Georgia. Data were collected on demographics, conduct of and perceived barriers to Pap smear testing, knowledge about HPV and HPV vaccination, and willingness to receive education and training about HPV and cervical cancer. Univariate counts and proportions were calculated. Pap smear testing and barriers were compared across demographics using bivariate and Poisson regression with robust error variance methods.

RESULTS

Overall, 54% of physicians never performed Pap smears; most reported testing was not their responsibility. Most (88%) obstetricians/gynecologists performed Pap smears. Younger physicians were more likely to perform Pap smears. Approximately 48% of physicians actively offered the HPV vaccine. Most physicians were receptive to increased education and training about HPV and cervical cancer.

CONCLUSION

Age-related differences in the conduct of and attitudes toward Pap smear testing exist among Georgian physicians. There is an opportunity to increase Pap smear testing and provide evidence-based HPV vaccine counseling in Georgia.

Travel and migration associated infectious diseases morbidity in Europe, 2008

BACKGROUND

Europeans represent the majority of international travellers and clinicians encountering returned patients have an essential role in recognizing, and communicating travel-associated public health risks.

METHODS

To investigate the morbidity of travel associated infectious diseases in European travellers, we analysed diagnoses with demographic, clinical and travel-related predictors of disease, in 6957 ill returned travellers who presented in 2008 to EuroTravNet centres with a presumed travel associated condition.

RESULTS

Gastro-intestinal (GI) diseases accounted for 33% of illnesses, followed by febrile systemic illnesses (20%), dermatological conditions (12%) and respiratory illnesses (8%). There were 3 deaths recorded; a sepsis caused by Escherichia coli pyelonephritis, a dengue shock syndrome and a Plasmodium falciparum malaria.GI conditions included bacterial acute diarrhea (6.9%), as well as giardiasis and amebasis (2.3%). Among febrile systemic illnesses with identified pathogens, malaria (5.4%) accounted for most cases followed by dengue (1.9%) and others including chikungunya, rickettsial diseases, leptospirosis, brucellosis, Epstein Barr virus infections, tick-borne encephalitis (TBE) and viral hepatitis. Dermatological conditions were dominated by bacterial infections, arthropod bites, cutaneous larva migrans and animal bites requiring rabies post-exposure prophylaxis and also leishmaniasis, myasis, tungiasis and one case of leprosy. Respiratory illness included 112 cases of tuberculosis including cases of multi-drug resistant or extensively drug resistant tuberculosis, 104 cases of influenza like illness, and 5 cases of Legionnaires disease. Sexually transmitted infections (STI) accounted for 0.6% of total diagnoses and included HIV infection and syphilis. A total of 165 cases of potentially vaccine preventable diseases were reported. Purpose of travel and destination specific risk factors was identified for several diagnoses such as Chagas disease in immigrant travellers from South America and P. falciparum malaria in immigrants from sub-Saharan Africa. Travel within Europe was also associated with health risks with distinctive profiles for Eastern and Western Europe.

CONCLUSIONS

In 2008, a broad spectrum of travel associated diseases were diagnosed at EuroTravNet core sites. Diagnoses varied according to regions visited by ill travellers. The spectrum of travel associated morbidity also shows that there is a need to dispel the misconception that travel, close to home, in Europe, is without significant health risk.

Timeliness of vaccination and its effects on fraction of vaccinated population

Delayed vaccination against childhood diseases may lead to increased mortality and morbidity among children and also affect the fraction of vaccinated population necessary for elimination of a disease. The purpose of this study was to assess the extent of the delay in vaccinations in four countries belonging to Commonwealth of Independent States and to assess how the timeliness of vaccination affects the vaccination coverage. The fraction of children vaccinated with delay was substantial in all the studied countries, and the impact of differences between countries was stronger than individual risk factors assessed in this study. In presence of vaccination delay, up-to-date vaccination is a biased estimator of the fraction of vaccinated population. Age-appropriate vaccination should be taken into account when assessing vaccination coverage.

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.

Diphtheria remains a threat to health in the developing world: an overview

Changes in the epidemiology of diphtheria are occurring worldwide. A large proportion of adults in many industrialized and developing countries are now susceptible to diphtheria. Vaccine-induced immunity wanes over time unless periodic booster is given or exposure to toxigenic Corynebacterium diphtheriae occurs. Immunity gap in adults coupled with large numbers of susceptible children creates the potential for new extensive epidemics. Epidemic emergencies may not be long in coming in countries experiencing rapid industrialization or undergoing sociopolitical instability where many of the factors thought to be important in producing epidemic such as mass population movements and difficult hygienic and economic conditions are present. The continuous circulation of toxigenic C. diphtheriae emphasizes the need to be aware of epidemiological features, clinical signs, and symptoms of diphtheria in vaccine era so that cases can be promptly diagnosed and treated, and further public health measures can be taken to contain this serious disease. This overview focused on worldwide data obtained from diphtheria with particular emphasis to main factors leading to recent epidemics, new clinical forms of C. diphtheriae infections, expression of virulence factors, other than toxin production, control strategies, and laboratory diagnosis procedures.

Diphtheria in Lithuania, 1986-1996

Diphtheria reappeared in Lithuania in 1986 and rose to epidemic levels by 1992. Between 1991 and 1996, 110 cases of diphtheria were registered, with an incidence of 0.03-1.15/100,000 population. Most cases (84%) and all 17 deaths occurred among persons >/=15 years, most of whom had never been vaccinated. Persons 40-49 years old had the highest average annual age-specific morbidity (1.70/100,000) and mortality (0.53/100,000) rates. Low levels of immunity among individuals 40-49 years old and migration to epidemic areas in Russia and Belarus contributed to the epidemic's occurrence. Between 1991 and 1995, toxigenic Corynebacterium diphtheriae strains were isolated from 84 of all registered patients (76%), and nontoxigenic strains were isolated from 13 (12%). By 1996, two mass vaccination campaigns, which provided one dose of vaccine to individuals 25-30 years old and three doses of vaccine to persons 31-60 years old, helped reduce the number of cases. The first campaign achieved 69% coverage; the second achieved 48% coverage.

Diphtheria in Latvia, 1986-1996

After nearly two decades without a diphtheria case in Latvia, the disease reappeared in 1986. From 1990 to 1996, case counts were highest among adults 40-49 years of age, school-aged children, and adolescents. Nonetheless, the average annualized incidence of disease was highest among infants and preschoolers. In August 1995, mass vaccination efforts began to provide adults 25-60 years of age with at least one dose of vaccine. By the end of the year, a 77% coverage rate was achieved, resulting in a decrease of reported diphtheria cases by 1996. From February to September 1997, special outreach efforts were focused on hard-to-reach populations; as a result, by June 1997, 55% of adults had received three doses of vaccine. While decreases in the incidence of and morbidity from diphtheria have occurred, additional efforts still need to be concentrated on improving vaccination coverage in adults and children <2 years of age and in reducing mortality from diphtheria.

Epidemic investigation of diphtheria, Republic of Kazakhstan, 1990-1996

The diphtheria epidemic that began in Russia in 1990 reached Kazakhstan in 1992 when 45 case-patients (a 50% increase over 1991) were reported. In 1993, 82 case-patients were reported, and 489 were reported in 1994. The epidemic peaked in 1995 when 1105 case-patients were reported (incidence rate=6.7/100,000 population). In 1996, after public health practice modifications and several mass vaccinations, 455 case-patients were reported. From 1990 to 1996, children </=14 years old represented 35% (2234) of the reported case-patients (and 33% of the population) but had a disproportionate share (49%) of the fatalities. Females represented 63% of the adult case-patients. In 1996, 297 (65%) of 455 case-patients and 26 (84%) of 31 fatalities were unvaccinated. Kazakhstan controlled the diphtheria epidemic by using a multifaceted public health strategy of prevention and control, which included changing the routine immunization schedule, modifying the official list of contraindications to vaccination, conducting mass campaigns to vaccinate persons, and treating close contacts of case-patients with antibiotics.

Epidemic diphtheria in Belarus, 1992-1997

In 1990, epidemic diphtheria reemerged in Russia and spread to Belarus in 1992, when 66 cases were reported. Diphtheria cases doubled each year in 1993 and 1994 and peaked in 1995, when 322 cases were reported. Intensified routine immunization of young children and mass vaccination of older children and selected groups of adults were conducted in 1995 and were followed by mass vaccination campaigns targeting all adults in 1996. By the end of 1996, full immunization of >95% of children and coverage of>87% of adults with >/=1 dose resulted in a rapid decline in diphtheria cases. In 1998, only 36 cases of diphtheria were reported. More than 70% of the 965 cases and 26 fatalities reported during 1990-1998 occurred among persons >14 years of age. High levels of immunity among the entire population are needed for rapid control of diphtheria epidemics in the vaccine era.

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.

Universal immunization: the diphtheria control strategy of choice in the Republic of Tajikistan, 1993-1997

During the 1993-1997 diphtheria epidemic in Tajikistan, the incidence rate was the highest observed throughout the Newly Independent States of the former Soviet Union (76.2 cases/100,000 population in 1995). Factors that contributed to this situation included an increase in the number of persons who were not fully immunized, a breakdown of health care services and disease surveillance, civil war, an increase in migration, shortages of qualified medical personnel, and shortages of products, resources, and services. The Ministry of Health and numerous international organizations have worked to address the needs of the republic, and in the fourth quarter of 1995, the number of reported cases began to decrease. It is believed that this decrease was largely the result of routine immunization, implementation of national immunization days, and use of a World Health Organization-recommended system for working with patients and contacts, and it underscores the importance of universal diphtheria immunization with special booster doses in such an epidemic setting.

Diphtheria epidemic in the Republic of Uzbekistan, 1993-1996

The Republic of Uzbekistan, like the other Newly Independent States in the 1990s, experienced epidemic diphtheria during the 1990s. The outbreak in Uzbekistan began in 1993 in southern regions that bordered areas of Tajikistan that were experiencing a very intense diphtheria epidemic. However, the Uzbek epidemic rapidly spread and threatened to involve the entire country. From 1993-1996, 1169 cases of diphtheria were reported, compared with 58 in 1990-1992. Unvaccinated or only partially vaccinated cases were more likely to have clinically severe forms of diphtheria than those who were fully vaccinated. Strong epidemiologic links with the Tajik diphtheria epidemic and the predominance of mitis biotype strains of Corynebacterium diphtheriae in Uzbekistan make it likely that the Uzbek outbreak arose independently of the predominantly biotype gravis epidemic that began in Russia. The epidemic appeared to be due to low population immunity and the large-scale reintroduction of toxigenic strains of C. diphtheriae. Several mass vaccination campaigns and general enhancement of routine immunization procedures led to control of the epidemic in 1996.

Diphtheria in the Russian Federation in the 1990s

A resurgence of diphtheria spread throughout the Russian Federation in the early 1990s; diphtheria had been well controlled, but circulation of toxigenic strains of Corynebacterium diphtheriae had persisted since the implementation of universal childhood vaccination in the late 1950s. More than 115,000 cases and 3,000 deaths were reported from 1990 to 1997, and, in contrast to the situation in the prevaccine era, most of the cases and deaths occurred among adults. Contributing factors included the accumulation of susceptible individuals among both adults and children and probably the introduction of new strains of C. diphtheriae. Vaccine quality, vaccine supply, or access to vaccine providers did not significantly contribute to the epidemic. Mass vaccination of adults and improved childhood immunization controlled the epidemic. High levels of population immunity, especially among children, will be needed to prevent and control similar outbreaks in the future.

Epidemic investigation of diphtheria in the Republic of Armenia, 1990-1996

While incidence rates of diphtheria steadily declined in Armenia after World War II, reemergence of the disease in 1990 brought about changes in public health practices and identified resource needs. The Armenian Ministry of Health (MOH) routinely collected diphtheria case reports, as a reportable health outcome. Diphtheria incidence rates increased from 0.02/100,000 in 1993 to 1/100,000 (36 cases) in 1994. The distribution of cases showed that the greatest number of illnesses and deaths occurred among persons 5-14 years old, yet incidence rates among persons 1-4 and 5-14 years old were similar (4. 4 cases/ and 4.3 cases/100,000, respectively). During 1990-1996, 9 (75%) of 12 cases who died and 18 (21%) of 84 cases who survived had not been vaccinated. The diphtheria epidemic in Armenia was an important, serious, and signal public health event. The Armenian MOH responded by revising immunization practices (1994), improving epidemic control measures (1995), and soliciting international resources (1992-1996).

Epidemic diphtheria in the 1990s: Azerbaijan

The diphtheria epidemic in the former Soviet Union reached Azerbaijan in 1991, when 66 cases of diphtheria were reported, a number that compared with 4 cases in 1990. From 1990-1996, 2182 cases of diphtheria and 286 diphtheria fatalities (case fatality rate: 13.1%) were reported in Azerbaijan, primarily among persons 5-39 years of age. Almost 45% of cases and 61% of deaths occurred among children 5-14 years of age. The high burden of severe disease among children and young adults suggested a different pattern of preexisting immunity against diphtheria in the Azerbaijani population than was observed in the concurrent diphtheria epidemic in Russia. Because resources were limited in Azerbaijan, mass immunization of the population was carried out in stages, focusing initially on school-aged children. Mass immunization campaigns targeting children were moderately successful in stabilizing the epidemic; mass immunization campaigns targeting both adults and children were eventually needed to fully stop the epidemic.