Influenza vaccine effectiveness in preventing hospitalizations with laboratory-confirmed influenza in Greece during the 2014-2015 season: A test-negative study.

The 2014-2015 influenza season was marked by circulation of antigenically drifted A/H3N2 strains, raising the possibility of low seasonal influenza Vaccine Effectiveness (VE). We assessed VE against hospitalization with laboratory-confirmed influenza for the 2014-2015 season, using routine surveillance data. Non-sentinel swab samples from Greek hospital inpatients were tested for influenza by RT-PCR in three laboratories, covering the entire country. We estimated VE using a test-negative design. Out of 883 patients with known vaccination status, 161 (18.2%) were vaccinated, and 392/883 patients (44.4%) tested positive for influenza, of whom 162 (41.3%) had type B and 151 (38.5%) had A/H3N2. Adjusted VE was 31.6% (95%CI: 2.9-51.8%) against any influenza, 46.8%, 95%CI: 12.5-67.6%) against type B and -1.9%, 95%CI: -69.5 to 38.7%) against A/H3N2. VE against non-ICU hospitalization appeared to be higher, but the difference did not reach statistical significance. Circulating A/H3N2 viruses showed substantial antigenic drift, while about half of the type B strains were similar to the vaccine strain. Despite the antigenic drift of the A/H3N2 strains, the vaccine still offered substantial protection against hospitalization with laboratory-confirmed influenza, mostly due to a surge in type B influenza late in the season. Vaccine coverage was low, even among groups targeted for vaccination, and considerable effort should be made to improve it. J. Med. Virol. 88:1896-1904, 2016. © 2016 Wiley Periodicals, Inc.

Challenges in antigenic characterization of circulating influenza A(H3N2) viruses during the 2011-2012 influenza season: an ongoing problem?

Genetic and antigenic characterization of 37 representative influenza A(H3N2) virus strains isolated in Greece during the 2011-2012 winter season was performed to evaluate matching of the viruses with the seasonal influenza vaccine strain A/Perth/16/2009. Hemagglutinin gene sequence analysis revealed that all Greek strains clustered within the Victoria/208 genetic clade. Furthermore, substitutions in the antigenic and glycosylation sites suggested potential antigenic drift. Our hemagglutination inhibition (HI) analysis showed that the Greek viruses were Perth/16-like; however, these viruses were characterized as Victoria/208-like when tested at the United Kingdom WHO Collaborating Centre (CC) with HI assays performed in the presence of oseltamivir, a finding consistent with the genetic characterization data. Variability in the HI test performance experienced by other European laboratories indicated that antigenic analysis of the A(H3N2) virus has limitations and, until its standardization, national influenza reference laboratories should include genetic characterization results for selection of representative viruses for detailed antigenic analysis by the WHO CCs.

Evaluation of tuberculosis underreporting in Greece through comparison with anti-tuberculosis drug consumption.

Surveillance is an integral part of tuberculosis (TB) control. Greece has a low TB notification rate, but there are doubts about underreporting. Examining anti-TB drug consumption is a way to validate the results of surveillance and estimate TB burden in the country. We used surveillance data from 2004 to 2008 to calculate the average prescribed treatment duration with the first-line anti-TB drugs isoniazid, rifampicin, ethambutol and pyrazinamide. We then obtained the best available data on consumption of these drugs, and calculated the number of treated cases to which these quantities correspond. We thus estimated underreporting at around 80% (77-81%), and annual TB incidence at about 30 cases per 100,000 population, five times over the notification rate. Underreporting was found to be constant over the study period, while incidence followed a decreasing trend. In addition we estimated that one person receives chemoprophylaxis for latent tuberculosis infection (LTBI) for every three TB cases. These results indicate the need for a comprehensive plan to improve TB surveillance and TB contact tracing in Greece, especially in light of the economic crisis affecting the country since 2009.

A gastroenteritis outbreak caused by noroviruses in Greece.

In June 2006, an outbreak alert regarding cases of acute gastroenteritis in a region in North Eastern Greece (population 100,882 inhabitants), triggered investigations to guide control measures. The outbreak started the first days of June, and peaked in July. A descriptive epidemiological study, a virological characterization of the viral agent identified from cases as well as a phylogenetic analysis was performed. From June 5 to September 3, 2006 (weeks 23-44), 1,640 cases of gastroenteritis (45.2% male and 54.8% female, aged 3 months to 89 years) were reported. The overall attack rate for the period was 16.3 cases/1,000 inhabitants. About 57% of cases observed were under the age of 15 years. Analysis of faecal samples identified Norovirus GII strains. Fifteen different Norovirus GII strains were recorded, presenting a homology of 94.8% (86-97%) to GII strains obtained from GenBank. The long duration of the outbreak suggests an important role of person-to-person transmission, while the emergence of the outbreak was possibly due to contaminated potable water, although no viruses were detected in any tested water samples. This outbreak underscores the need for a national surveillance system for acute non-bacterial gastroenteritis outbreaks.

Fatal cases associated with pandemic influenza A (H1N1) reported in Greece.

Between 18 May 2009 and 3 May 2010, a total of 149 fatal cases associated with pandemic influenza A (H1N1) were reported in Greece. Detailed case-based epidemiological information was available for the large majority of fatal cases. The time distribution follows an epidemic curve with a peak in the beginning of December 2009 and a second peak one month later. This is similar to that of laboratory confirmed cases and influenza-like illness cases from our sentinel surveillance system, with two weeks delay. The most commonly reported underlying conditions were chronic cardiovascular disease and immunosuppression, while the most frequently identified risk factor was obesity. These findings should be taken into consideration, when vaccination strategies are employed.

Mycobacterium tuberculosis transmission among high school students in Greece.

BACKGROUND: The aim of this study was to investigate the requirements and practical steps for screening of Mycobacterium tuberculosis (MTB) transmission among high school student populations in two regional high schools of central Greece. Case-matched control populations from other regional schools were included. METHODS: Case study of two indexed cases, 61 close contacts, 212 casual contacts and 369 controls were investigated. Detailed questionnaires, tuberculin-skin test (PPD test), chest radiography, medical evaluation and DNA fingerprinting of sputum isolates were used. RESULTS: In case A, three (1.97%) of 152 close and casual contacts developed tuberculosis, and a further 25 (16.4%) were classified as infected. In contrast, none of the 121 close or casual contacts investigated for Case B developed tuberculosis or were classified as infected. None of the control populations contained infected individuals. Contacts of case A had a much higher risk (3.08 < RR = 22.29 < 161.69, P < 0.001) of being infected than contacts of case B. Two different strains of MTB were found responsible for these outbreaks. CONCLUSION: There was a considerable difference in the infectivity of the two cases presumably due to environmental and clinical factors, although two different MTB strains were responsible. It is proposed that the extent of case investigation should be individualized with particular emphasis placed among close contacts.