Prevalence of circulating antibodies against hemagglutinin of influenza viruses in epidemic season 2021/2022 in Poland.

The aim of the study was to determine the level of anti-hemagglutinin antibodies in the serum of patients during the 2021/2022 epidemic season in Poland. A total of 700 sera samples were tested, divided according to the age of the patients into 7 age groups: 0-4 years of age, 5-9 years of age, 10-14 years of age, 15-25 years of age, 26-44 years of age, 45-64 years of age and ≥65 years of age, 100 samples were collected from each age group. Anti-hemagglutinin antibody levels was determined using the haemagglutination inhibition assay (OZHA). The results obtained confirm the presence of anti-hemagglutinin antibodies for the antigens A/Victoria/2570/2019 (H1N1) pdm09, A/Cambodia/e0826360/2020 (H3N2), B/Washington/02/2019 and B/Phuket/3073/2013 recommended by World Health Organization (WHO) for the 2021/2022 epidemic season. The analysis of the results shows differences in the levels of individual anti-hemagglutinin antibodies in the considered age groups. In view of very low percentage of the vaccinated population in Poland, which was 6.90% in the 2021/2022 epidemic season, the results obtained in the study would have to be interpreted as the immune system response in patients after a previous influenza virus infection.

Hemagglutinin Antibodies in the Polish Population during the 2019/2020 Epidemic Season.

The aim of the study was to determine the level of antibodies against hemagglutinin of influenza viruses in the serum of subjects belonging to seven different age groups in the 2019/2020 epidemic season. The level of anti-hemagglutinin antibodies was tested using the hemagglutination inhibition (HAI) test. The tests included 700 sera from all over Poland. Their results confirmed the presence of antibodies against the following influenza virus antigens: A/Brisbane/02/2018 (H1N1)pdm09 (48% of samples), A/Kansas/14/2017/ (H3N2) (74% of samples), B/Colorado/06/ 2017 Victoria line (26% of samples), and B/Phuket/3073/2013 Yamagata line (63% of samples). The level of antibodies against hemagglutinin varied between the age groups. The highest average (geometric mean) antibody titer (68.0) and the highest response rate (62%) were found for the strain A/Kansas/14/2017/ (H3N2). During the epidemic season in Poland, only 4.4% of the population was vaccinated.

Analysis of Infections Caused by Influenza Viruses and Influenza-Like Viruses in the Population of People over 65 Years of Age in the 2019-2020 Epidemic Season in Poland.

BACKGROUND Influenza can be the most dangerous for people in risk groups, for example for seniors, in whom it can lead to serious and life-threatening complications. The aim of this research was to analyze the activity of influenza viruses and influenza-like viruses in patients over 65 years of age in the 2019-2020 epidemic season in Poland. MATERIAL AND METHODS A total of 1269 samples collected from patients over 65 years of age with suspected influenza or other respiratory viruses in the 2019-2020 epidemic season (from October 1, 2019, to September 30, 2020) were analyzed. The test material was nose and throat swabs collected during the 2019-2020 epidemic season. Quantitative polymerase chain reaction was used to determine the influenza virus type and subtype for positive samples. RESULTS Among the confirmed infections with influenza viruses, cases due to influenza A were dominant, and the dominant subtype was influenza A subtype A/H1N1/pdm09. Infections with influenza-like viruses were also confirmed in the patients participating in the study, with the presence of genetic material of respiratory syncytial viruses confirmed most often. CONCLUSIONS Seasonal vaccinations can significantly reduce the number of cases and thus the risk of post-influenza complications and deaths among seniors. This is very important, especially now, due to the current epidemiological situation related to the ongoing SARS-CoV-2 respiratory virus pandemic.

Importance of Influenza Anti-Hemagglutinin Antibodies During the SARS-CoV-2 Pandemic in the 2019/2020 Epidemic Season in Poland.

BACKGROUND The aim of this study was to determine the level of anti-hemagglutinin antibodies in the serum of recovered patients during the SARS-CoV-2 pandemic in the 2019/2020 epidemic season in Poland, and the course of COVID-19. MATERIAL AND METHODS The material for the study consisted of the sera of COVID-19 convalescents obtained from the following 9 Regional Blood Donation and Blood Supply Centers located in 8 voivodeships. The hemagglutination inhibition reaction assay (HAI) using 8 viral hemagglutination units was used to determine antibody levels, in accordance with WHO recommendations. RESULTS This research confirms that a patient's declared severity of the course of SARS-CoV-2 infection is influenced by the patient's age and concomitant diseases. There was no statistically significant correlation between the level of anti-hemagglutinin antibodies and the severity of the course of a SARS-CoV-2 infection. Based on the serological tests conducted, it can be unequivocally concluded that both vaccinated and influenza-infected patients had a response rate in line with the requirements of the European Commission and the Committee for Medicinal Products for Human Use hemagglutinin antibodies for 4 influenza virus antigens tested. CONCLUSIONS Patients who confirmed their antibody levels with the Commission of the European Communities and the Committee for Propriety Medicinal Products (CPMP) requirements had a mild COVID-19 course. The results of our research emphasize the role of anti-hemagglutinin antibodies in the course of SARS-CoV-2 infection. COVID-19 convalescents have a higher response rate against all 4 types of anti-hemagglutinin antibodies analyzed.

Influenza and Influenza-Like Respiratory Virus Infections in Children During the 2019/20 Influenza Seazon and the COVID-19 Pandemic in Poland: Data from the Department of Influenza Research, the National Influenza Center at the National Institute of Public Health, National Institute of Hygiene-National Research Institute and 16 Voivodeship Sanitary and Epidemiological Stations

BACKGROUND This population study aimed to investigate influenza and influenza-like respiratory virus infections in children during the 2019/20 influenza season and the coronavirus disease 2019 (COVID-19) pandemic in Poland. MATERIAL AND METHODS This study analyzed data from the National Influenza Centre, the Department of Influenza Research at the National Institute of Public Health, and 16 Voivodeship Sanitary and Epidemiological Stations in Poland. Nose and throat swabs were obtained from children during the 2019/20 influenza season and the COVID-19 pandemic. Viral RNA detection was performed using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) to diagnose influenza virus infection and viral subtypes. RESULTS In the analyzed group, both cases of influenza A and B and infections with influenza-like viruses were confirmed. Among all cases caused by influenza viruses, influenza A was more frequent than B, with predominance of the A/H1N1/pdm09 subtype. The flu-like virus which infected most children was the human respiratory syncytial virus (RSV). The greatest number of cases with RSV was registered in the group of the youngest children (0-4 years). CONCLUSIONS This population study from Poland showed that during the COVID-19 pandemic, and during the winter influenza season of 2019/20, influenza and influenza-like viral infections in children showed some differences from previous influenza seasons. The findings highlight the importance of viral infection surveillance and influenza vaccination in the pediatric population.

Immunogenicity of Split Inactivated Quadrivalent Influenza Vaccine in Adults with Obesity in the 2017/2018 Season.

BACKGROUND Obesity is associated with susceptibility to severe influenza infection and several disturbances of the immune response to the influenza vaccine. However, the effect of obesity on the immunogenicity of the influenza vaccine is not fully understood. Our objective here was to assess the immunogenicity of the split, inactivated quadrivalent influenza vaccine (QIV) in Polish adults with obesity. MATERIAL AND METHODS Fifty-three subjects with obesity aged 21-69 years were vaccinated with the QIV in 2017/2018 season. Antibody titers against the 4 vaccine strains were measured using the hemagglutination inhibition (HI) assay. The mean fold antibody increase (MFI), seroprotection rate (protection rate, PR), and seroconversion rate (response rate, RR) were calculated to assess vaccine immunogenicity. RESULTS The vaccine elicited a significant increase in the anti-HI titers against the QIV antigens. The MFI, PR, and RR for the QIV antigens also reached the required age-specific values, indicating the QIV meets current immunogenicity criteria. Individuals with class I and class II/III obesity had similar anti-HI titers, MFI, PR, and RR to each of the vaccine strains. Adults aged <60 years had similar anti-HI titers, MFI, PR, and RR to the QIV strains to those aged ≥60 years. CONCLUSIONS Our results indicate that the split virion, inactivated QIV is immunogenic in adults with obesity regardless of their degree of obesity and age (ie, <60 and ≥60 years).

Spread of Influenza Viruses in Poland and Neighboring Countries in Seasonal Terms.

In Poland, flu supervision is coordinated by the National Influenza Center at the National Institute of Public Health-National Institute of Hygiene. In this publication, we want to determine geographical trends in influenza virus circulation in the region. A detailed analysis of virological and epidemiological data showed the course of the epidemic season in Poland, as well as in neighboring countries. The spatial differentiation of the incidence of infection between voivodships was examined, as well as compared to countries that border a given voivodship. The results show a significant variation in the incidence of infection in terms of time and space. This points to the need to increase the number of tests and to raise awareness among health care professionals and the public about the probability of an influenza pandemic, as undetected viruses can spread further into the European Union.

Subtypes of Influenza Virus Infection and Outcomes in Individuals Older than 65 Years of Age in Poland in the 2016/2017 to 2019/2020 Epidemic Seasons.

BACKGROUND Influenza is a viral disease causing many deaths each season. With aging, the human immune system becomes weaker, so people over the age of 65 years are at higher risk of complications after influenza infections. This population study, conducted in Poland, aimed to identify the subtypes of influenza virus infection and outcomes in individuals more than 65 years of age in the 2016/2017 to 2019/2020 epidemic seasons. MATERIAL AND METHODS The research materials were nose and throat swabs. Research was conducted in 16 Voivodship Sanitary and Epidemiological Stations and in the Department of Influenza Research, National Influenza Centre, NIPH-NIH. Methods of RNA isolation depended on the laboratory where the isolation was performed. In all laboratories, quantitative polymerase chain reaction (qRT-PCR) was used to determine the influenza virus type and subtype. RESULTS The analysis of the incidence of influenza among people over the age of 65 included the 2016/2017, 2017/2018, 2018/2019, and 2019/2020 influenza epidemic seasons. We analyzed the percentage of positive samples, the dynamics of epidemic seasons, and the percentage share of influenza viruses in the 65+ age group, according to the epidemic season and percentage of deaths. CONCLUSIONS This population study showed that, in Poland, between the 2016/2017 and 2019/2020 epidemic seasons, people who were more than 65 years of age were at higher risk of influenza virus infection and its complications. The findings support the importance of seasonal influenza vaccination in the population over age 65 years.

Serum Vitamin D and Immunogenicity of Influenza Vaccination in the Elderly.

Vaccination is the most effective preventive measure that reduces the risk of influenza and post-influenza complications. It prevents influenza-related hospitalizations and deaths in 50-60% and about 80% of patients aged over 65, respectively. There is the clinical plausibility of the association between serum vitamin D (VIT D) content and viral respiratory infections. In this study, we addressed the issue of a vitamin D modulatory effect on the immune response to seasonal influenza vaccination in elderly persons. The study comprised 96 participants aged 60-75 during the 2016/17 epidemic season. After the determination of the baseline content of VIT D and anti-hemagglutinin antibodies (H1, H3, and HB), participants were vaccinated with a trivalent vaccine. The content of the anti-hemagglutinin antibodies was rechecked 4-5 weeks afterward, showing inappreciable alterations. The negative findings of this study make the influence of serum VIT D content on the immunogenicity of influenza vaccination highly unlikely in elderly persons.

Epidemic Influenza Seasons from 2008 to 2018 in Poland: A Focused Review of Virological Characteristics.

The objective of this review was to elaborate on changes in the virological characteristics of influenza seasons in Poland in the past decade. The elaboration was based on the international influenza surveillance system consisting of Sentinel and non-Sentinel programs, recently adopted by Poland, in which professionals engaged in health care had reported tens of thousands of cases of acute upper airway infections. The reporting was followed by the provision of biological specimens collected from patients with suspected influenza and influenza-like infection, in which the causative contagion was then verified with molecular methods. The peak incidence of influenza infections has regularly been in January-March each epidemic season. The number of tested specimens ranged from 2066 to 8367 per season from 2008/2009 to 2017/2018. Type A virus predominated in nine out of the ten seasons and type B virus of the Yamagata lineage in the 2017/2018 season. Concerning the influenza-like infection, respiratory syncytial virus predominated in all the seasons. There was a sharp increase in the proportion of laboratory confirmations of influenza infection from season to season in relation to the number of specimens examined, from 3.2% to 42.4% over the decade. The number of confirmations, enabling a prompt commencement of antiviral treatment, related to the number of specimens collected from patients and on the virological situation in a given season. Yet influenza remains a health scourge, with a dismally low yearly vaccination rate, which recently reaches just about 3.5% of the general population in Poland.

Quadrivalent Influenza Vaccine-Induced Antibody Response and Influencing Determinants in Patients ≥ 55 Years of Age in the 2018/2019 Season.

The effects of immunization with subunit inactivated quadrivalent influenza vaccine (QIV) are not generally well assessed in the elderly Polish population. Therefore, this study evaluated vaccine-induced antibody response and its determinants. METHODS: Consecutive patients ≥ 55 years old, attending a Primary Care Clinic in Gryfino, Poland, received QIV (A/Michigan/ 45/2015(H1N1)pdm09, A/Singapore/INFIMH-16-0019/2016 (H3N2), B/Colorado/06/2017, B/Phuket/ 3073/2013) between October-December 2018. Hemagglutination inhibition assays measured antibody response to vaccine strains from pre/postvaccination serum samples. Geometric mean titer ratio (GMTR), protection rate (PR) and seroconversion rate (SR) were also calculated. RESULTS: For 108 patients (54.6% males, mean age: 66.7 years) the highest GMTR (61.5-fold) was observed for A/H3N2/, then B/Colorado/06/2017 (10.3-fold), A/H1N1/pdm09 (8.4-fold) and B/Phuket/ 3073/2013 (3.0-fold). Most patients had post-vaccination protection for A/H3N2/ and B/Phuket/3073/ 2013 (64.8% and 70.4%, respectively); lower PRs were observed for A/H1N1/pdm09 (41.8%) and B/Colorado/06/ 2017 (57.4%). The SRs for A/H3N2/, A/H1N1/pdm09, B Victoria and B Yamagata were 64.8%, 38.0%, 46.8%, and 48.2%, respectively. Patients who received QIV vaccination in the previous season presented lower (p < 0.001 and p = 0.03, respectively) response to B Victoria and B Yamagata. CONCLUSIONS: QIV was immunogenic against the additional B lineage strain (B Victoria) without significantly compromising the immunogenicity of the other three vaccine strains, therefore, adding a second B lineage strain in QIV could broaden protection against influenza B infection in this age group. As the QIV immunogenicity differed regarding the four antigens, formulation adjustments to increase the antigen concentration of the serotypes that have lower immunogenicity could increase effectiveness. Prior season vaccination was associated with lower antibody response to a new vaccine, although not consistent through the vaccine strains.

Ocular Complications in Influenza Virus Infection.

Purpose: To describe a case series of ocular complications associated with upper respiratory tract infections. Methods: Four patients aged 21-61 years (three females, one male) had confirmed ocular complications connected with a general upper respiratory tract infection with myalgia and fever. Ophthalmological examination, including a visual acuity test, a slit-lamp exam, intraocular pressure measurements, fluorescein and indocyanine green angiography, optical coherence tomography (OCT), and diagnostic tests for influenza were performed in the patients (RT-PCR, HAI). Results: Acute posterior multifocal placoid pigment epitheliopathy (APMPPE) was diagnosed in three patients and serous macular detachment (SME) in one. Influenza virus infection was confirmed by molecular biological methods (RT-PCR) or the hemagglutination inhibition test (HAI) in two patients. All patients were treated with systemic prednisone. Conclusion: A coincidence between APMPPE and SME epitheliopathy and influenza virus infection was observed in different months of a given epidemic season.

Vaccine Effectiveness against Influenza in 2015/16 in Hospital and Ambulatory Medical Care Facilities: Polish Results of the European I-MOVE+ Multicenter Study.

Influenza vaccination is the best measure available to prevent seasonal influenza infection. The majority of studies on vaccine effectiveness in the 2015/16 season conducted in the European I-MOVE+ Project, show that a match between the circulating influenza strains in the general public and those included in the vaccine for the Northern Hemisphere was low to moderate. As part of I-MOVE+, Poland has implemented a case control negative study design and molecular biology methods, such as real time RT-PCR, to assess the vaccine match and effectiveness. The research described herein consisted of two major influenza vaccine effectiveness investigations conducted in Poland in the 2015/16 season. The general practice part of the study included 228 cases consisting of 159 type A, 65 type B, and 4 coinfections (types A + B), and 312 negative control cases. The hospital study part included 26 cases consisting of 21 type A, 2 type B, and 3 coinfections, and 13 negative control cases. The data were collected from patients of all ages recruited by 46 volunteering doctors in 15 Poland's provinces and three hospitals, respectively. In both study parts, only were seven patients and 12 control subjects vaccinated. Low vaccine coverage, a major limitation of the Polish study, makes the calculation of vaccine effectiveness for the Polish population hardly applicable statistically. Despite the crudeness of data, they were included into the common European analysis. The overall vaccine effectiveness amounted to 21.0% (95% CI: 74-122). It was somehow better for type B virus: 53.9% (95% CI: 47-87) and type A virus: 23.6% (95% CI: 83-185). A larger sample size is needed to achieve a desired interpretation of results on influenza vaccine effectiveness in Poland.

The Lethal Spanish Influenza Pandemic in Poland.

The Spanish influenza pandemic in the years 1918-1920 was the largest and most tragic pandemic of infectious disease in human history. Deciphering the structure of the virus (including the determination of complete genome sequence) of this pandemic and the phylogenetic analysis and explanation of its virulence became possible thanks to molecular genetic analysis of the virus isolated from the fixed and frozen lung tissue of influenza victims who died in 1918 and were buried frozen in Alaska and Spitsbergen. Epidemiological data from the course of this pandemic in Poland have not been previously published. For analysis, we used source materials such as clinical studies and case reports of doctors fighting against the pandemic and registries of influenza cases in units of the Polish Army and military hospitals. Clinically, the pandemic of 1918 was characterized by the same symptoms and course as influenza in other years. Pathologically, the disease was similar to the other pandemic, in that the destruction was mostly limited to the respiratory tract. The "Spanish" influenza pandemic of 1918-1920 took place in Poland in 3 epidemic waves. The peaks of morbidity and mortality occurred in the capital, Warsaw, in December 1918 and in December 1919 to January 1920. It is estimated that throughout the pandemic period of 1918-1920 in Poland, 200 000 to 300 000 people died.

Observation and Clinical Pattern in Patients with White Dot Syndromes: The Role of Color Photography in Monitoring Ocular Changes in Long-Term Observation.

BACKGROUND The aim of this study was to assess the clinical course and distinctive features of different white dot syndromes (WDS) in patients attending the Ophthalmology Department, Medical University of Warsaw in the years 1995-2015. MATERIAL AND METHODS Sixty-two (62) patients (43 females and 19 males), aged 18 to 77 years, referred with a WDS were included in this prospective study, with observation period ranging from 5 months to 16 years. All patients underwent a complete ophthalmological examination and multimodal imaging studies. RESULTS In this cohort of 62 patients, the following WDS entities were identified: multifocal choroiditis with panuveitis (MFCPU), multifocal choroiditis (MFC), punctate inner choroidopathy (PIC), birdshot, acute posterior multifocal placoid pigment epitheliopathy (APMPPE), subretinal fibrosis and uveitis, multiple evanescent white dot syndrome (MEWDS), serpiginous choroiditis, and single cases of acute annular outer retinopathy (AAOR). CONCLUSIONS The study was performed at a Polish referral center and may to some extent reflect the varied geographical distribution of white dot syndromes, as none of the subjects was found to suffer from acute zonal occult outer retinopathy (AZOOR), acute macular neuroretinopathy (AMN), or diffuse unilateral subacute neuroretinitis (DUSN). Long-term follow-up is warranted by the evolution of lesions in the eye fundus, while management depends on correct diagnosis of WDS. When the posterior pole is involved in some cases of the WDS an immunosuppressive treatment, the use of the PDT or anti-VEGF injections were necessary.

Rapid Influenza Diagnostic Tests Improve Suitability of Antiviral Treatment in Hospitalized Children.

Influenza may have a complicated course in young children. The aim of the study was to analyze the suitability of influenza treatment among children younger than 5 years hospitalized due to an influenza-like illness. We conducted a comparison of the treatment among children hospitalized in two consecutive years: 2015, when no rapid influenza diagnostic tests (RIDT) were in use, and 2016, when RIDT were implemented into a routine practice in the pediatric ward. In both seasons, nasopharyngeal swabs were collected and examined with real time qRT-PCR. In the 2015 season, influenza was diagnosed in 15/52 (28 %) children and none of them received oseltamivir, while 14/15 (93 %) patients received antibiotics. In the 2016 season, influenza was diagnosed in 11/63 (17 %) children, 7/11 (64 %) of them received oseltamivir and another 7/11 (64 %) received antibiotics. In four cases antibiotics overlapped oseltamivir. These differences in the use of oseltamivir and antibiotics were statistically significant (p < 0.05). We conclude that the implementation of RIDT improves the suitability of influenza treatment and decreases the frequency of antibiotic therapy. RIDT should be available in pediatric departments to optimize influenza treatment.

Influenza Vaccination Coverage Among Polish Patients with Chronic Diseases.

Patients at a high-risk of severe influenza, because of their underlying health disorders, are recommended to receive a seasonal influenza vaccination. In Poland, influenza coverage rate in the general population is very low (3.4 %). However, there is little known about the coverage rate among high-risk patients. The aim of this study was to describe a general knowledge, perception, and influenza vaccination coverage rate among Polish patients with enhanced risk for influenza. We conducted a self-reported survey among 500 patients with chronic disorders: 120 pulmonary, 80 hemodialyzed, 100 thyroid cancer, and 200 cardiovascular patients. We found the following influenza vaccination coverage in the respective groups of patients: 58 % in pulmonary, 34 % in hemodialyzed, 32 % in cardiovascular, and 9 % in thyroid cancer patients. The difference between the coverage rate in pulmonary patients compared with the other risk groups was significant (p < 0.05). In pulmonary patients, the most important barrier for influenza vaccination was a lack of recommendations from healthcare workers, while a high awareness of influenza was the most powerful driver for vaccination (p < 0.05). We conclude that although the influenza vaccination coverage in Polish patients with chronic diseases is higher than that reported in the general population, this rate remains much below the recommended level and should be improved.

Influenza in Poland in 2013 and 2013/2014 epidemic season

OBJECTIVE: Analysis of epidemiological situation of influenza in Poland in 2013 and 2013/14 epidemic season in reference to previous years and seasons. MATERIAL AND METHODS: Analysis was based on: 1) data collected within influenza routine surveillance system in Poland, including data published in annual bulletins "Infectious diseases and poisonings in Poland" as well as unpublished data gathered in the Department of Epidemiology of the NIPH-NIH; 2) data collected within influenza system - Sentinel, and beyond this system, concerning results of virological tests carried out in 2013/14 epidemic season in the Department of Influenza Research, National Influenza Center in the NIPHNIH and/or laboratories of provincial sanitary and epidemiological stations which are gathered in the National Influenza Center. RESULTS: Compared to 2012, the number of influenza and influenza-like cases increased more than twofold in 2013 in Poland. A total of 3 164 405 cases were reported. Incidence was 8 218.7 per 100,000 population (33 733.2 in 0-4 age group). As many as 0.45% of patients were referred to hospitals. According to the data of the Central Statistical Office, 115 deaths due to influenza were notified. Based on the data of the sanitary inspection (incomplete data), the percentage of population vaccinated against influenza was 2.4% (7.7% of persons aged more than 64 years). A total of 2 780 945 cases were registered in 2013/14 epidemic season. Its peak was reported in March 2014. Incidence was 7 224.0 per 100,000 population (35 172.8 in 0-4 age group). Compared to 2012/13 epidemic season, it was lower by 8.0%. Incidence rates ranged from 29 339.6 in pomorskie voivodeship to 1 306.5 in lubuskie voivodeship. Nearly a half of all cases (48.7%) were registered in children and adolescents up to 15 years. As many as 0.34% of patients were referred to hospitals (0.87% of persons aged more than 64 years). From the data of the Central Statistical Office transpires that 8 deaths due to influenza were reported in epidemic season. Type A influenza subtype H3N2 predominated in all influenza cases. Human respiratory syncytial virus (RSV) was the dominant agent in other viral infections of respiratory tract. Antigenic analysis of influenza strains showed their affinity with vaccine strains of the vaccine recommended for this epidemic season. CONCLUSIONS: In spite of slow improvements, influenza and influenza-like surveillance system in Poland is still not homogeneous and stable enough. It hinders the assessment of current epidemiological situation. For instance, there are difficulties in determining what is the effect of modifications in the surveillance on the increase in the number of influenza and influenza-like cases observed in Poland in recent years. A low percentage of population vaccinated against influenza (with a decreasing trend beginning from 2005) suggests a necessity of revising the methods of promotion and organization of these vaccines used so far. One of the public health priorities should be to increase the percentage of vaccinated population up to the average level in EU countries.

[Influenza surveillance]. / Nadzór nad grypa.

Influenza surveillance was established in 1947. From this moment WHO (World Health Organization) has been coordinating international cooperation, with a goal of monitoring influenza virus activity, effective diagnostic of the circulating viruses and informing society about epidemics or pandemics, as well as about emergence of new subtypes of influenza virus type A. Influenza surveillance is an important task, because it enables people to prepare themselves for battle with the virus that is constantly mutating, what leads to circulation of new and often more virulent strains of influenza in human population. As vaccination is the most effective method of fighting the virus, one of the major tasks of GISRS is developing an optimal antigenic composition of the vaccine for the current epidemic season. European Influenza Surveillance Network (EISN) has also developed over the years. EISN is running integrated epidemiological and virological influenza surveillance, to provide appropriate data to public health experts in member countries, to enable them undertaking relevant activities based on the current information about influenza activity. In close cooperation with GISRS and EISN are National Influenza Centres--national institutions designated by the Ministry of Health in each country.