The Impact of the COVID-19 Pandemic on Influenza Transmission in Poland.

BACKGROUND: The aim of this study was to determine whether the occurrence of the SARS-CoV-2 pandemic affected the incidence of influenza in Poland and the efficiency of the SENTINEL influenza surveillance system. METHODS: The analysis was based on virologic data from the 2018/2019-2021/2022 epidemic seasons. The data in question were obtained from the SENTINEL influenza surveillance system, which is utilized in Poland. RESULTS: In the 2020/2021 epidemic season, only one positive case was confirmed. In the epidemic season of 2021/2022, the number of positive cases increased. There was a delay in the peak of the season, since the start of pandemic, which was observed in the 14th week of 2022. Previously, it was recorded in the 5-10th week, depending on the season. Before the pandemic, the number of positive samples in relation to the tested ones oscillated between 41-49.4%. After the pandemic, it was 0.3% and below 20%, respectively, for season 2020/2021 and season 2021/2022. CONCLUSIONS: The COVID-19 pandemic caused a decline in many other infectious diseases, including influenza, as a result of the numerous lockdowns and from people shifting to remote work. Other safety measures, such as obligatory protective masks and the use of disinfectants, had a significant impact on reducing the number of cases.

Association between the Seroprevalence of Antibodies against Seasonal Alphacoronaviruses and SARS-CoV-2 Humoral Immune Response, COVID-19 Severity, and Influenza Vaccination

The present study assesses the seroprevalence of antibodies against seasonal human alphacoronaviruses 229E and NL63 among adult patients infected with SARS-CoV-2, and its association with the humoral response to SARS-CoV-2 infection and its severity, and influenza vaccination. A serosurvey was conducted to quantify the presence of IgG antibodies against the nucleocapsid of 229E (anti-229E-N) and NL63 (anti-NL63-N), and anti-SARS-CoV-2 IgG antibodies (against nucleocapsid, receptor-binding domain, S2 domain, envelope, and papain-like protease) for 1313 Polish patients. The seroprevalence of anti-229E-N and anti-NL63 in the studied cohort was 3.3% and 2.4%. Seropositive individuals had a higher prevalence of anti-SARS-CoV-2 IgG antibodies, higher titers of the selected anti-SARS-CoV2 antibodies, and higher odds of an asymptomatic SARS-CoV-2 infection (OR = 2.5 for 229E and OR = 2.7 for NL63). Lastly, the individuals vaccinated against influenza in the 2019/2020 epidemic season had lower odds of seropositivity to 229E (OR = 0.38). The 229E and NL63 seroprevalence was below the expected pre-pandemic levels (up to 10%), likely due to social distancing, increased hygiene, and face masking. The study also suggests that exposure to seasonal alphacoronaviruses may improve humoral responses to SARS-CoV-2 while decreasing the clinical significance of its infection. It also adds to accumulating evidence of the favorable indirect effects of influenza vaccination. However, the findings of the present study are of a correlative nature and thereby do not necessarily imply causation.

Association between the Seroprevalence of Antibodies against Seasonal Alphacoronaviruses and SARS-CoV-2 Humoral Immune Response, COVID-19 Severity, and Influenza Vaccination.

The present study assesses the seroprevalence of antibodies against seasonal human alphacoronaviruses 229E and NL63 among adult patients infected with SARS-CoV-2, and its association with the humoral response to SARS-CoV-2 infection and its severity, and influenza vaccination. A serosurvey was conducted to quantify the presence of IgG antibodies against the nucleocapsid of 229E (anti-229E-N) and NL63 (anti-NL63-N), and anti-SARS-CoV-2 IgG antibodies (against nucleocapsid, receptor-binding domain, S2 domain, envelope, and papain-like protease) for 1313 Polish patients. The seroprevalence of anti-229E-N and anti-NL63 in the studied cohort was 3.3% and 2.4%. Seropositive individuals had a higher prevalence of anti-SARS-CoV-2 IgG antibodies, higher titers of the selected anti-SARS-CoV2 antibodies, and higher odds of an asymptomatic SARS-CoV-2 infection (OR = 2.5 for 229E and OR = 2.7 for NL63). Lastly, the individuals vaccinated against influenza in the 2019/2020 epidemic season had lower odds of seropositivity to 229E (OR = 0.38). The 229E and NL63 seroprevalence was below the expected pre-pandemic levels (up to 10%), likely due to social distancing, increased hygiene, and face masking. The study also suggests that exposure to seasonal alphacoronaviruses may improve humoral responses to SARS-CoV-2 while decreasing the clinical significance of its infection. It also adds to accumulating evidence of the favorable indirect effects of influenza vaccination. However, the findings of the present study are of a correlative nature and thereby do not necessarily imply causation.

IgG autoantibodies against ACE2 in SARS-CoV-2 infected patients.

How frequently autoantibodies against angiotensin-converting enzyme 2 (ACE2) occur in patients infected by SARS-CoV-2 is understudied and limited to investigations on a small sample size. The presence of these antibodies may contribute to the long-lasting effects of COVID-19 observed in some individuals, particularly if IgG-class antibodies would emerge in patients. This study assessed the prevalence of IgG autoantibodies against ACE2 in 1139 patients infected with SARS-CoV-2 and examined their relationship with severity, demographic characteristics, and status of vaccination against influenza. The overall prevalence of anti-ACE IgG antibodies in our cohort was 1.5%. Most of these individuals were men (76.5%) and underwent mild COVID-19, but some severe and asymptomatic cases were also observed. Patients with severe infection had twofold higher titers than mild and asymptomatic cases. Age, comorbidities, and influenza vaccination status were not related to antibody prevalence. The prevalence of IgG anti-SARS-CoV-2 antibodies (against nucleocapsid protein and S2 subunit, but not against receptor-binding domain) was higher in the subset with ACE2 autoantibodies. Further research is required to understand the potential spectrum and duration of effects of IgG autoantibodies against ACE2 in patients after SARS-CoV-2 infection, particularly concerning long COVID-19.

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.

Relationship between Humoral Response in COVID-19 and Seasonal Influenza Vaccination.

There is evidence that vaccination against seasonal influenza can improve innate immune responses to COVID-19 and decrease disease severity. However, less is known about whether it could also impact the humoral immunity in SARS-CoV-2 infected patients. The present study aimed to compare the SARS-CoV-2 specific humoral responses (IgG antibodies against nucleocapsid; anti-N, receptor binding domain; anti-RBD, subunit S2; anti-S2, and envelope protein; anti-E) between non-hospitalized, COVID-19 unvaccinated, and mild COVID-19 convalescent patients who were and were not vaccinated against influenza during the 2019/2020 epidemic season (n = 489 and n = 292, respectively). The influenza-vaccinated group had significantly higher frequency and titers of anti-N antibodies (75 vs. 66%; mean 559 vs. 520 U/mL) and anti-RBD antibodies (85 vs. 76%; mean 580 vs. 540 U/mL). The prevalence and concentrations of anti-S2 and anti-E antibodies did not differ between groups (40-43%; mean 370-375 U/mL and 1.4-1.7%; mean 261-294 U/mL) and were significantly lower compared to those of anti-RBD and anti-N. In both groups, age, comorbidities, and gender did not affect the prevalence and concentrations of studied antibodies. The results indicate that influenza vaccination can improve serum antibody levels produced in response to SARS-CoV-2 infection.

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.

The determination of haemagglutinin influenza antibodies in the Polish population in the epidemic season 2020/2021 during the SARS-CoV-2 pandemic.

The aim of the study was to prove the level of antibodies against haemagglutinin in the sera of people from seven age groups in the epidemic season 2020/2021 in Poland to determine the differentiation of the antibody level and the protection rate depending on age. The level of anti-haemagglutinin antibodies was established by haemagglutinin inhibition test (HAI). A total of 700 randomly selected sera from people belonging to 7 different age groups were tested. The results confirmed the presence of antibodies against the following influenza antigens: A/Guangdong-Maonan/SWL1536/2019 (H1N1)pdm09-like virus, A/Hong Kong/2671/2019 (H3N2)-like virus, B/Washington/02/2019 (B/Victoria lineage)-like virus and B/Phuket/3073/2013 (B/Yamagata lineage)-like virus. The level of haemagglutinin antibodies varied between the studied age groups, with the highest values in the 5-9 age group and the lowest in the 0-4 age group. It was also proven that the protection rate was the highest for the A/Hong Kong/2671/2019(H3N2)-like virus antigen, which exceeded the protection level in the 5 age groups. Considering the very low percentage of people vaccinated in the epidemic season 2020/2021 in Poland, which amounted to only 6.1%, the results should be interpreted as the immune system's response to an infection with influenza virus.

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.

Molecular diagnosis of COVID-19 ­ present experiences / Molekularna diagnostyka COVID-19 ­ dotychczasowe doswiadczenia.

Severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2), a new highly emerging and pathogenic for human RNA virus, is responsible for the present COVID-19 pandemic. Molecular diagnostic methods, including real-time reverse transcription-PCR (RT-PCR) assay are the recommended methods for the identification and laboratory confirmation of COVID-19 cases. RT-PCR allows for detection the RNA of the virus in clinical specimens from patients suspected of COVID-19 with high specificity and sensitivity. Testing is still crucial for rapid detection of infected persons, implementation of appropriate measures to suppress further virus transmission and mitigate its impact. In response to demand of a molecular diagnostic test for SARS-CoV-2, within a first few months ongoing pandemic many commercial kits has become available on the market. However, these tests have varied in number and type of molecular targets, time of reaction as well as quality. In this study we compared different commercial tests for the detection of SARS-CoV-2 in clinical samples sending to Laboratory of Department of Virology, NIPH-NIH.