Measles epidemiology and elimination strategies in Turkey

The effect of targeted wide age range SIAs in reducing measles incidence in the African Region

Periodic measles supplemental immunisation activities (SIAs) increase population immunity and thereby reduce the pool of accumulated susceptible children. They are typically conducted every 2 - 4 years, and most often target children up to five years of age. Between 2012 and 2015, after surveillance data indicated a shift in the epidemiological profile of measles towards older age groups, 11 countries were supported to conduct wide age range SIAs based on their local epidemiological patterns. Six other countries conducted SIAs with measles-rubella vaccines targeting ages 9 months to 14 years as an initial step of introducing rubella vaccine into the immunization program. In subsequent years, the incidence of confirmed measles dropped significantly in 13 of the 17 countries reviewed. The findings emphasize the importance of well-functioning surveillance systems, and the benefits of using of surveillance data to determine the specific target age-range for periodic SIAs to accelerate progress towards measles elimination.

Association between seroprevalence of measles and various social determinants in the year following a measles outbreak in Turkey

OBJECTIVES

Despite an ongoing measles elimination programme, a measles outbreak occurred in 2013 in Turkey. Population-based seroprevalence studies are needed to determine seronegativity and explore the reasons for this outbreak. This study aimed to explore the seroprevalence of measles and its association with various social determinants in a provincial population in Turkey in the year following a measles outbreak.

STUDY DESIGN

Cross-sectional study.

METHODS

This study was conducted in Manisa Province in 2014 in a sample of 1740 people aged >2 years. The dependent variable was the seroprevalence of measles. Independent variables were sex, age, migration, household size, household density, income, education level, existence of chronic disease and occupational class. Blood samples were collected from participants at family health centres. The presence of specific measles antibodies in serum samples was determined using an anti-measles virus IgG enzyme-linked immunosorbent assay test. Chi-squared test and logistic regression analysis were performed.

RESULTS

Overall, data from 1250 people were analysed. The seroprevalence of measles in the whole study population was 82.2% (95% confidence interval 80.0-84.2). Seroprevalence was 55.4% among subjects aged 2-9 years, 48.7% among subjects aged 10-19 years, 74.1% among subjects aged 20-29 years and 93.6% among subjects aged 30-39 years (P < 0.01). Seroprevalence in subjects aged >40 years was >95%. The lowest seroprevalence was found in primary school children (40.2%), followed by those below the age for primary education (69.8%) and secondary school graduates (75.1%). The prevalence of measles seronegativity was not associated with any of the social determinants when adjusted for age.

CONCLUSIONS

The seroprevalence of measles was lower than expected in the study population and was particularly low in subjects aged <30 years of age despite previous vaccination. Seroprevalence was not associated with social determinants of health that confirmed either an even distribution of virus exposure or fair access to vaccination services. However, the current seroprevalence cannot be sufficiently effective to reach the measles elimination targets, suggesting that it may be necessary to re-evaluate the need for an extra dose of measles vaccine.

Synthesis of Evidence to Characterize National Measles and Rubella Exposure and Immunization Histories

Population immunity depends on the dynamic levels of immunization coverage that countries achieve over time and any transmission of viruses that occur within the population that induce immunity. In the context of developing a dynamic transmission model for measles and rubella to support analyses of future immunization policy options, we assessed the model inputs required to reproduce past behavior and to provide some confidence about model performance at the national level. We reviewed the data available from the World Health Organization (WHO) and existing measles and rubella literature for evidence of historical reported routine and supplemental immunization activities and reported cases and outbreaks. We constructed model input profiles for 180 WHO member states and three other areas to support disease transmission model development and calibration. The profiles demonstrate the significant variability in immunization strategies used historically by regions and member states and the epidemiological implications of these historical choices. The profiles provide a historical perspective on measles and rubella immunization globally at the national level, and they may help immunization program managers identify existing immunity and/or knowledge gaps.

Towards measles elimination: Phylogenetic analysis of measles viruses in Turkey (2012-2013) and identification of genotype D8

Molecular characterization of different measles virus (MV) strains is essential to combat the disease. Sixty measles MV strains were obtained from throat swabs or urine of patients in Turkey between 2012 and 2013 and characterized. MV RNA sequences (n = 60) were analysed for 456 nucleotides representing hypervariable domain of the nucleoprotein (N) gene. Of the 60 strains analysed 53 were the D8 genotype, 6 were B3, 1 was D4, and 1 was A. This report describes MV genotype D8 that was involved in a measles outbreak in Turkey. Sequences of most genotype D8 strains (n = 51) were identical to the sequence of variant D8-Frankfurt-Main, which has been associated with outbreaks throughout Europe. Despite the lack of epidemiologic information, a phylogenetic analysis suggested that the genotype D8 MV may have been brought to Turkey from elsewhere. Phylogenetic and epidemiological findings suggested that strains identified in tourists and associated with importation included one strain of genotype D8, one strain of genotype B3, and one strain of genotype D4. These findings from the 2012 to 2013 outbreak in Turkey confirm that pockets of unimmunised individuals are making the country susceptible to measles outbreaks. To prevent further outbreaks, deliberate and sustained effort must be made to reach, and immunise susceptible age groups. Towards measles elimination process, continued molecular surveillance of measles strains in Turkey will help identify transmission patterns of virus and evaluate vaccination efforts. J. Med. Virol. 88:1867-1873, 2016. © 2016 Wiley Periodicals, Inc.

Susceptibility to measles, rubella, mumps, and varicella-zoster viruses among healthcare workers

BACKGROUND

It is important to identify and immunize susceptible healthcare workers to prevent and control hospital infections. Our aim was to evaluate the specific antibodies against the measles, mumps, and rubella viruses and the varicella zoster virus among healthcare workers in a tertiary-care hospital.

PATIENTS AND METHODS

A total of 284 healthcare workers (89 men and 195 women; mean age, 33.5 ± 11 years), including 111 nurses, 87 physicians, 34 laboratory technicians, and 52 members of the housekeeping staff, of Van Training and Research Hospital were enrolled in this study. Antibodies were detected with an enzyme-linked immunosorbent assay.

RESULTS

The numbers of workers with serological susceptibility to mumps, measles, rubella, or chicken pox were 26 (9.2%), 18 (6.3%), 7 (2.5%), and 5 (1.8%), respectively. Although the difference was not statistical significant, the rate of seroprevalence of antibodies was lowest for measles (90.8%; p>0.05). Susceptibility to measles, mumps, and rubella, and chicken pox was more prevalent among young healthcare workers (p<0.001). Not all healthcare workers born before 1957 were immune to these vaccine-preventable diseases.

CONCLUSION

These data confirm that screening and vaccination of susceptible healthcare workers is essential regardless of age.

Molecular characterization of measles viruses in Turkey (2010-2011): first report of genotype D9 involved in an outbreak in 2011

Genetic characterization of measles viruses (MVs) combined with acquisition of epidemiologic information is essential for measles surveillance programs used in determining transmission pathways. This study describes the molecular characterization of 26 MV strains (3 from 2010, 23 from 2011) obtained from urine or throat swabs harvested from patients in Turkey. MV RNA samples (n = 26) were subjected to sequence analysis of 450 nucleotides comprising the most variable C-terminal region of the nucleoprotein (N) gene. Phylogenetic analysis revealed 20 strains from 2011 belonged to genotype D9, 3 to D4, 2 strains from 2010 to genotype D4 and 1 to genotype B3. This study represents the first report describing the involvement of MV genotype D9 in an outbreak in Turkey. The sequence of the majority of genotype D9 strains was identical to those identified in Russia, Malaysia, Japan, and the UK. Despite lack of sufficient epidemiologic information, the presence of variants observed following phylogenetic analysis suggested that exposure to genotype D9 might have occurred due to importation more than once. Phylogenetic analysis of five genotype D4 strains revealed the presence of four variants. Epidemiological information and phylogenetic analysis suggested that three genotype D4 strains and one genotype B3 strain were associated with importation. This study suggests the presence of pockets of unimmunized individuals making Turkey susceptible to outbreaks. Continuing molecular surveillance of measles strains in Turkey is essential as a means of acquiring epidemiologic information to define viral transmission patterns and determine the effectiveness of measles vaccination programs designed to eliminate this virus.

Protection of medical and paramedical university students in Lebanon against measles, mumps, rubella and varicella: active measures are needed

OBJECTIVE

In many countries, universities require students to either show a physician-certified proof of immunity or to get vaccinated against measles, mumps, rubella and varicella, prior to their registration in medical and paramedical majors. The objective of this study was to evaluate the need to implement this policy in Lebanon.

DESIGN

A cross-sectional study was performed on students of the Lebanese University (LU), faculties of Medicine, Dentistry, Pharmacy and Public Health.

METHODS

The serological immunity status was assessed by determining specific antibody titer and the disease and vaccination history of 502 students was collected. Based on percentages of susceptibility, a cost-effectiveness analysis was performed to compare systematic vaccination without prior serological testing with selective vaccination of seronegative students.

RESULTS

Percentages of individuals with serologically confirmed immunity against varicella, measles, rubella and mumps were 93%, 86%, 88% and 75% respectively, and 42% of the students were susceptible to at least one of the pathogens covered by the MMR vaccine. Compilation of 186 vaccination records indicated that only 19 students (10%) had been adequately vaccinated. Moreover, among those, 7 students (37%) were still unprotected against at least one virus. Systematic vaccination against MMR was found to be 4-5 times less expensive than selective vaccination, while selective vaccination of seronegative individuals was more cost-efficient for varicella.

CONCLUSION

Since, in this population, very few individuals were able to present a proof of adequate vaccination, it is recommended to systematically vaccinate healthcare students in Lebanon against MMR. For varicella, selective vaccination after serological testing should be performed.

Completeness of hepatitis, brucellosis, syphilis, measles and HIV/AIDS surveillance in Izmir, Turkey

Background

According to the surveillance system in Turkey, most diseases are notified only by clinicians, without involving laboratory notification. It is assumed that a considerable inadequacy in notifications exists; however, this has not been quantified by any researcher. Our aim was to evaluate the completeness of communicable disease surveillance in the province of Izmir, Turkey for the year of 2003 by means of estimating the incidences of diseases.

Methods

Data on positive laboratory results for the notifiable and serologically detectable diseases hepatitis A, B, C, brucellosis, syphilis, measles and HIV detected in 2003 in Izmir (population 3.5 million) were collected from serology laboratories according to WHO surveillance standards and compared to the notifications received by the Provincial Health Directorate. Data were checked for duplicates and matched. Incidences were estimated with the capture-recapture method. Sensitivities of both notifications and laboratory data were calculated according to these estimates.

Results

Among laboratories performing serologic tests (n = 158) in Izmir, 84.2% accepted to participate, from which 23,515 positive results were collected. Following the elimination of duplicate results as well as of cases residing outside of Izmir, the total number was 11,402. The total number of notifications was 1802. Notification rates of cases found in laboratories were 31.6% for hepatitis A, 12.1% for acute hepatitis B, 31.8% for brucellosis, 25.9% for syphilis and 100% for HIV confirmation.

Conclusions

It was discovered that for hepatitis A, B, C, brucellosis and syphilis, there is a considerable under-notification by clinicians and that laboratory data has the potential of contributing greatly to their surveillance. The inclusion of laboratories in the surveillance system of these diseases could help to achieve completeness of reporting.

Health worker densities and immunization coverage in Turkey: a panel data analysis

BACKGROUND

Increased immunization coverage is an important step towards fulfilling the Millennium Development Goal of reducing childhood mortality. Recent cross-sectional and cross-national research has indicated that physician, nurse and midwife densities may positively influence immunization coverage. However, little is known about relationships between densities of human resources for health (HRH) and vaccination coverage within developing countries and over time. The present study examines HRH densities and coverage of the Expanded Programme on Immunization (EPI) in Turkey during the period 2000 to 2006.

METHODS

The study is based on provincial-level data on HRH densities, vaccination coverage and provincial socioeconomic and demographic characteristics published by the Turkish government. Panel data regression methodologies (random and fixed effects models) are used to analyse the data.

RESULTS

Three main findings emerge: (1) combined physician, nurse/midwife and health officer density is significantly associated with vaccination rates--independent of provincial female illiteracy, GDP per capita and land area--although the association was initially positive and turned negative over time; (2) HRH-vaccination rate relationships differ by cadre of health worker, with physician and health officers exhibiting significant relationships that mirror those for aggregate density, while nurse/midwife densities are not consistently significant; (3) HRH densities bear stronger relationships with vaccination coverage among more rural provinces, compared to those with higher population densities.

CONCLUSION

We find evidence of relationships between HRH densities and vaccination rates even at Turkey's relatively elevated levels of each. At the same time, variations in results between different empirical models suggest that this relationship is complex, affected by other factors that occurred during the study period, and warrants further investigation to verify our findings. We hypothesize that the introduction of certain health-sector policies governing terms of HRH employment affected incentives to provide vaccinations and therefore relationships between HRH densities and vaccination rates. National-level changes experienced during the study period--such as a severe financial crisis--may also have affected and/or been associated with the HRH-vaccination rate link. While our findings therefore suggest that the size of a health workforce may be associated with service provision at a relatively elevated level of development, they also indicate that focusing on per capita levels of HRH may be of limited value in understanding performance in service provision. In both Turkey and elsewhere, further investigation is needed to corroborate our results as well as gain deeper understanding into relationships between health worker densities and service provision.

Intra- and intergenotype characterization of D6 measles virus genotype

Determination of inter- and intragenotype stability and variability are the basic tools for the molecular epidemiology and evolutionary investigation of measles virus (MV). We made a comparison between complete genome sequences of four MVs (two wt MV strains-WA.USA/17.98 and 97-45881, and two SSPE MV strains-MVs/Zagreb.CRO/47.02/and MVs/Zagreb.CRO/08.03/), all belonging to genotype D6. Results of analyses clearly confirm that MV genome continuously changes within the viruses of the same or different genotypes by accumulation of mutations in different parts of the genome. Only a small number of these accumulated mutations induce amino acid substitutions and thus possibly introduce new biological characteristics or a new genotype over a long time period. This study clearly reveals a long untranslated region between M and F genes as the most variable region of the MV genome and detects the presence of unique residues on the level of the entire genome as a new important parameter in the investigation of molecular evolution of MVs.

Measles, rubella, mumps, and varicella seroprevalence among health care workers in Turkey: is prevaccination screening cost-effective?

BACKGROUND

To investigate the immune status of health care workers (HCWs) against measles, rubella, mumps, and varicella zoster (MMRV) in Turkey and to define an appropriate vaccination program among HCWs.

METHODS

Voluntary HCWs from a children's hospital and a general hospital were included in the study between March and May 2005. The specific IgG antibodies against MMRV viruses were screened by ELISA.

RESULTS

Three hundred sixty-three HCWs participated in the study; 186 (51%) were physicians, 118 (33%) were nurses, 36 (10%) were housekeeping staff, and 23 (6%) were medical technicians. The proportion of HCWs who had antibodies against measles was 98.6%; rubella, 98.3%; mumps, 92.2%; and varicella, 98%. No association was found between the susceptibility to at least 1 of MMRV virus infections and gender, age, duration of work, profession, and department of work in analysis either among the whole study group, or each hospital. The positive predictive value for the history of varicella was 100%, whereas it was 92% for MMR. The cost of vaccination for varicella was significantly expensive without screening before vaccination. However, there was not much difference for MMR infections.

CONCLUSION

A policy based on obtaining the history of varicella infection from the staff and then screening the ones with negative history and vaccination of only seronegative HCWs was found to be appropriate.

Review of the temporal and geographical distribution of measles virus genotypes in the prevaccine and postvaccine eras

Molecular epidemiological investigation of measles outbreaks can document the interruption of endemic measles transmission and is useful for establishing and clarifying epidemiological links between cases in geographically distinct clusters. To determine the distribution of measles virus genotypes in the prevaccine and postvaccine eras, a literature search of biomedical databases, measles surveillance websites and other electronic sources was conducted for English language reports of measles outbreaks or genetic characterization of measles virus isolates. Genotype assignments based on classification systems other than the currently accepted WHO nomenclature were reassigned using the current criteria. This review gives a comprehensive overview of the distribution of MV genotypes in the prevaccine and postvaccine eras and describes the geographically diverse distribution of some measles virus genotypes and the localized distributions of other genotypes.

Genetic characterization of measles viruses isolated in Turkey during 2000 and 2001

BACKGROUND

Molecular epidemiologic studies have made significant contributions to measles surveillance activities by helping to identify source and transmission pathways of the virus. This report describes the genetic characterization of wild-type measles viruses isolated in Turkey in 2000 and 2001.

RESULTS

Wild-type measles viruses were isolated from 24 cases from five provinces in Turkey during 2001. The viruses were analyzed using the standard genotyping protocols. All isolates were classified as genotype D6, the same genotype that was identified in Turkey in previous outbreaks during 1998.

CONCLUSION

Turkey has begun implementation of a national program to eliminate measles by 2010. Therefore, this baseline genotype data will provide a means to monitor the success of the elimination program.

Laboratory investigations are indispensable to monitor the progress of measles elimination--results of the German Measles Sentinel 1999-2003

BACKGROUND

The elimination of measles is a goal set by the World Health Organisation to be reached by 2010 in the European region.

OBJECTIVES

To enhance the measles surveillance in Germany, a country-wide laboratory supported a sentinel was established.

STUDY DESIGN

A network of >1200 representatively distributed practitioners reported detailed data on all clinically diagnosed cases and provided specimens for laboratory diagnosis.

RESULTS

A total of 3225 suspected cases were reported between October 1999 and December 2003. The incidence in Western Germany decreased from >15 cases per 100,000 population to one case in 2003, while in Eastern Germany <1 case per 100,000 population was observed during these years. Laboratory investigations were undertaken in 40% of cases in 2000/2001. This rate increased to 79% in 2003. Simultaneously, the rate of confirmed cases dropped from 60% in the former years to 23% in 2003. Measles virus (MV) detection by serology and by PCR revealed concordant results in 92%. Most suspected cases (85%) were unvaccinated with 66% being laboratory confirmed. Only 10% of suspected cases occurred in vaccinated individuals and very few (22%) could be confirmed. Analyses of confirmed measles in vaccinated patients (n = 49) revealed 24.5% primary vaccine failures, 24.5% reinfections after successful vaccination and 31% MV infection before or shortly after vaccination. The genetic characterisation of 389 MV isolates identified eight genotypes: B3, C2, D4, D5, D6, D7, G2 and H1. Only the C2, D6 and D7 MV genotypes circulated endemically in Western Germany. The newly emerged MV D7 almost completely replaced the pre-existing C2 and D6 MVs in 2001. The few measles cases detected in Eastern Germany were mostly caused by imported MVs.

CONCLUSION

The data demonstrate that laboratory investigations including molecular methods are an indispensable tool for surveillance in all countries advanced in measles elimination.

The unfinished measles immunization agenda

Despite achieving and sustaining global measles vaccination coverage of about 80% over the past decade, worldwide measles remains the fifth leading cause of mortality among children aged <5 years. In May 2002, the United Nations Special Session on Children endorsed the goal of reducing measles deaths by half by 2005. Countries and World Health Organization (WHO) regions that adopted aggressive measles control or elimination strategies have shown excellent results. In 2001, countries in the Americas reported an all time low of 537 confirmed measles cases. Substantial progress in measles control has also been achieved in the WHO Western Pacific Region, in seven southern African countries, and in selected countries in WHO European, Eastern Mediterranean, and Southeast Asian regions. The ongoing measles disease burden and availability of safe and effective measles mortality reduction strategies make a compelling case to complete the unfinished agenda of measles immunization.