Key Considerations during the Transition from the Acute Phase of the COVID-19 Pandemic: A Narrative Review

New insights into the pathogenesis of SARS-CoV-2 during and after the COVID-19 pandemic

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the respiratory distress condition known as COVID-19. This disease broadly affects several physiological systems, including the gastrointestinal, renal, and central nervous (CNS) systems, significantly influencing the patient's overall quality of life. Additionally, numerous risk factors have been suggested, including gender, body weight, age, metabolic status, renal health, preexisting cardiomyopathies, and inflammatory conditions. Despite advances in understanding the genome and pathophysiological ramifications of COVID-19, its precise origins remain elusive. SARS-CoV-2 interacts with a receptor-binding domain within angiotensin-converting enzyme 2 (ACE2). This receptor is expressed in various organs of different species, including humans, with different abundance. Although COVID-19 has multiorgan manifestations, the main pathologies occur in the lung, including pulmonary fibrosis, respiratory failure, pulmonary embolism, and secondary bacterial pneumonia. In the post-COVID-19 period, different sequelae may occur, which may have various causes, including the direct action of the virus, alteration of the immune response, and metabolic alterations during infection, among others. Recognizing the serious adverse health effects associated with COVID-19, it becomes imperative to comprehensively elucidate and discuss the existing evidence surrounding this viral infection, including those related to the pathophysiological effects of the disease and the subsequent consequences. This review aims to contribute to a comprehensive understanding of the impact of COVID-19 and its long-term effects on human health.

The burden of infectious diseases throughout and after the COVID-19 pandemic (2020-2023) and Russo-Ukrainian war migration

Understanding how the infectious disease burden was affected throughout the COVID-19 pandemic is pivotal to identifying potential hot spots and guiding future mitigation measures. Therefore, our study aimed to analyze the changes in the rate of new cases of Poland's most frequent infectious diseases during the entire COVID-19 pandemic and after the influx of war refugees from Ukraine. We performed a registry-based population-wide study in Poland to analyze the changes in the rate of 24 infectious disease cases from 2020 to 2023 and compared them to the prepandemic period (2016-2019). Data were collected from publicly archived datasets of the Epimeld database published by national epidemiological authority institutions. The rate of most of the studied diseases (66.6%) revealed significantly negative correlations with the rate of SARS-CoV-2 infections. For the majority of infectious diseases, it substantially decreased in 2020 (in case of 83%) and 2021 (63%), following which it mostly rebounded to the prepandemic levels and, in some cases, exceeded them in 2023 when the exceptionally high annual rates of new cases of scarlet fever, Streptococcus pneumoniae infections, HIV infections, syphilis, gonococcal infections, and tick-borne encephalitis were noted. The rate of Clostridioides difficile enterocolitis was two-fold higher than before the pandemic from 2021 onward. The rate of Legionnaires' disease in 2023 also exceeded the prepandemic threshold, although this was due to a local outbreak unrelated to lifted COVID-19 pandemic restrictions or migration of war refugees. The influx of war migrants from Ukraine could impact the epidemiology of sexually transmitted diseases. The present analysis indicates that continued efforts are needed to prevent COVID-19 from overwhelming healthcare systems again and decreasing the control over the burden of other infectious diseases. It also identifies the potential tipping points that require additional mitigation measures, which are also discussed in the paper, to avoid escalation in the future.

Trends of Hepatitis A Virus Infection in Poland: Assessing the Potential Impact of the COVID-19 Pandemic and War in Ukraine

Hepatitis A virus (HAV) is the most common cause of acute viral hepatitis, which is preventable by vaccination. This study analyzed trends of HAV infections in Poland according to socio-demographic features in the years 2009-2022 and assessed the potential impact of the COVID-19 pandemic (2020-2023) and the migration of war refugees from Ukraine (since February 2022). In 2009-2022, 7115 new cases of HAV infection were diagnosed in Poland, especially among men (66.4%) and in urban areas (77.4%). Infections among men were most common at the age of 25-34 (median rate 0.43 per 105) and in women aged 15-24 (median rate 0.39 per 105). Analysis of the 14-year frequency of HAV infections exhibited three trends, regardless of gender, age, and residence. The infections revealed a downward trend in 2009-2014, increased significantly in 2014-2018, and decreased again after 2018. A particularly rapid increase in HAV infections occurred between March 2017 and February 2018 (median rate 0.79 per 105). The high level of new infections persisted until the beginning of the COVID-19 pandemic, at which point it dropped significantly but did not reach the level recorded before March 2017. During the Omicron SARS-CoV-2 dominance period, the median rate of HAV infections was 0.053 per 105, with a four-fold increase being observed from February 2022 (when the migration of war refugees from Ukraine began) to August 2022. The presented results can serve as a reference point for further observations in Central Europe. The HAV epidemiological situation is unlikely to escalate in Poland but requires further monitoring.

Influenza vaccination as a prognostic factor of humoral IgA responses to SARS-CoV-2 infection

There is evidence that influenza vaccination may provide additional benefits by inducing training of innate immunity and increasing humoral responses to heterologous challenges. Immunoglobulin A (IgA) antibodies dominate the early phase of the adaptive response to SARS-CoV-2 infection, but whether their production may be associated with previous influenza vaccination has not been a subject of any study. This study compared serum SARS-CoV-2-specific IgA responses, measured with Microblot-Array assay, in individuals who experienced COVID-19 (N = 1318) and differed in the status of the seasonal influenza vaccine, age, sex, and disease severity. Influenza-vaccinated individuals had a higher seroprevalence of IgA antibodies against nucleocapsid (anti-NP; by 10.1%), receptor-binding domain of spike protein (anti-RBD; by 11.8%) and the S2 subunit of spike protein (anti-S2; by 6.8%). Multivariate analysis, including age, sex, and COVID-19 severity, confirmed that receiving the influenza vaccine was associated with higher odds of being seropositive for anti-NP (OR, 95% CI = 1.57, 1.2-2.0), anti-RBD (OR, 95% CI = 1.6, 1.3-2.0), and anti-S2 (OR, 95% CI = 1.9, 1.4-2.7), as well as being seropositive for at least one anti-SARS-CoV-2 IgA antibody (OR, 95% CI = 1.7, 1.3-2.1) and all three of them (OR, 95% CI = 2.6, 1.7-4.0). Age ≥ 50 years was an additional factor predicting better IgA responses. However, the concentration of particular antibodies in seropositive subjects did not differ in relation to the influenza vaccination status. The study evidenced that influenza vaccination was associated with improved serum IgA levels produced in response to SARS-CoV-2 infection. Further studies are necessary to assess whether trained immunity is involved in the observed phenomenon.

Respiratory syncytial virus immunoprophylaxis: Novel opportunities and a call for equity

With the approval of the first vaccines against respiratory syncytial virus (RSV) and a novel RSV-neutralizing antibody, 2023 has been perceived as a game-changing year in preventing severe outcomes of RSV infections in infants and the elderly. However, the costs of these pharmaceuticals are high, while RSV disproportionately impacts populations of low-to-middle-income regions, which may continue to suffer from a lack of pharmaceutical measures for RSV prevention under health and socioeconomic disparities. This paper presents an overview of the characteristics, clinical results, and approval status of various RSV vaccines and anti-RSV antibodies. It posits that wealthy nations cannot monopolize RSV immunoprophylaxis and should work jointly to make it available to lower-income countries. An approach toward RSV immunoprophylaxis equity based on five points is offered: (1) integration of RSV vaccines and antibodies into the existing global humanitarian distribution systems, (2) using affordable RSV vaccine pricing models, (3) enforcing equity as a part of national and global public health strategy, (4) implementing equitable allocation frameworks for RSV immunoprophylaxis, and (5) promoting local manufacturing. Such a plan needs to be put into action as soon as possible to avoid delays in serving the populations with the highest needs related to RSV burden.

Effect of inactivated vaccine boosters against severe and critical COVID-19 during the Omicron BA.5 wave: A retrospective analysis of hospitalized patients in China

Few real-world analyses of the ability of vaccines to protect against severe COVID-19 have been published. In this real-world study, we compared the prevalence of severe or critical COVID-19 between patients at our hospital who were not vaccinated against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or who had been vaccinated partial, full, or booster course with the CoronaVac, containing inactivated virus propagated in Vero cells. Data from electronic health records were retrospectively analyzed for 4090 inpatients with COVID-19 who were treated at West China Hospital, Chengdu between December 6, 2022 and February 14, 2023. Clinicodemographic characteristics and COVID-19 severity were compared among patients who had been vaccinated 0, 1, 2 or more times with inactivated vaccine CoronaVac. To evaluate vaccine effectiveness over time, we plotted Kaplan-Meier curves with the percentage of patients with the outcome of severe or critical COVID-19 from the time of their last vaccine dose according to vaccination status. Ordinal logistic regression was used to assess associations between vaccination status and COVID-19 severity. Cox regression was used to identify risk factors for severe or critical COVID-19. Among the 4090 patients, 171 had been vaccinated partial and 423 twice with the full CoronaVac regimens, while 905 had been vaccinated three times (boosted). The prevalence of severe or critical COVID-19 among patients was 11 percentage points lower among those vaccinated (40%) at least twice than among those unvaccinated (51%) (p＜0.001), while it was 10% points lower among those who had received a booster (41%) than among those unvaccinated (51%) (p＜0.001). Protection against severe or critical COVID-19 due to vaccination was significantly weakened by being older than 65 years, being male, or having diabetes, chronic heart disease, autoimmune disease, or chronic lung disease. Completing a full course of immunization with inactivated vaccine CoronaVac against SARS-CoV-2 can reduce the risk of severe or critical COVID-19 due to the Omicron BA.5 subvariant.

Changing epidemiology of COVID-19: potential future impact on vaccines and vaccination strategies

INTRODUCTION

COVID-19 was an unprecedented challenge worldwide; however, disease epidemiology has evolved, and COVID-19 no longer constitutes a public health emergency of international concern. Nonetheless, COVID-19 remains a global threat and uncertainties remain, including definition of the end of the pandemic and transition to endemicity, and understanding true rates of SARS-CoV-2 infection/transmission.

AREAS COVERED

Six international experts convened (April 2023) to interpret changing COVID-19 epidemiology and public health challenges. We report the panel's recommendations and knowledge gaps in COVID-19 epidemiology, SARS-CoV-2 evolution, and future vaccination strategies, informed by peer-reviewed publications, surveillance data, health authority assessments, and clinical experience.

EXPERT OPINION

High population SARS-CoV-2 immunity indicates the likely end to the pandemic's acute phase. Continued emergence of variants/sublineages that can evade the vaccine-induced antibody response are likely, but widespread immunity reduces the risk of disease severity. Continued surveillance is required to capture transition to endemicity, seasonality, and emergence of novel variants/sublineages, to inform future vaccination strategies. COVID-19 vaccination should be integrated into routine vaccination programs throughout life. Co-circulation with other respiratory viruses should be monitored to avoid a combined peak, which could overrun healthcare systems. Effective, combined vaccines and improved education may help overcome vaccine hesitancy/booster fatigue and increase vaccination uptake.

Modeling the potential public health impact of different vaccination strategies with an adapted vaccine in South Africa

BACKGROUND

COVID-19 vaccines adapted to newly emerging circulating variants are necessary to better protect the population due to the evolving nature of the SARS-CoV-2 virus.

RESEARCH DESIGN AND METHODS

The South African population was stratified by age and risk (defined by comorbidities such as diabetes, obesity, smoking, cancer, and asthma), and HIV status. The outcomes of different vaccination strategies based on age, risk, and HIV status were estimated using a Markov-decision tree model based on age-specific inputs derived from the literature and South African surveillance data.

RESULTS

Vaccinating older adults and those with comorbidities was estimated to avert 111,179 infections 18,281 hospitalizations, and 3,868 deaths, resulting in savings of ZAR 1,260 million (USD 67 million) and ZAR 3,205 million (USD 170 million) in direct and indirect costs, respectively. Similar results were obtained when considering strategies targeting older adults and the HIV population. Expanding vaccination to 75% of the standard-risk population prevented more infections (401%), hospitalizations (167%), and deaths (67%) and increased the direct (232%) and indirect (455%) cost savings compared to the base case.

CONCLUSIONS

Implementing widespread vaccination strategies that utilize a vaccine adapted to the prevailing circulating variant in South Africa would result in significant public health and economic gains.