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Introduction: Several clinical manifestations have been discovered for COVID-19 since the emergence of SARS-CoV-2, which can be classified into early, medium, and long-term complications. However, late complications can be present after recovery from acute COVID-19 illness. The present study aims to comprehensively review the available evidence of late complications related to COVID-19. Method: A search was conducted, using keywords, through electronic databases, which included Scopus, Web of Science, PubMed, and Embase up to August 29, 2022. Study selection was performed according to a strict inclusion and exclusion criteria. The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) checklist was followed, and studies were appraised using the National Institute of Health (NIH) quality assessment and risk of bias tool. Results: In total, 50 studies were included, and nine distinct COVID-19 late complication categories were identified. A review of these studies revealed that neurologic and psychiatric (n=41), respiratory (n=27), musculoskeletal and rheumatologic (n=22), cardiovascular (n=9), and hepatic and gastrointestinal (n=6) complications were the most prevalent complications of long COVID-19. Conclusion: Almost all human body systems are affected by late complications of COVID-19 with different severity and prevalence. Fatigue and some other neuropsychiatric symptoms are the most common late complications among long COVID-19 patients. Respiratory symptoms including dyspnea (during exercise), cough, and chest tightness were the next most prevalent long-term complications of COVID-19. Since these complications are persistent and late, being aware of the signs and symptoms is essential for the healthcare providers and patients.

Abstract Background and Aims Alteration in humans' gut microbiota was reported in patients infected with severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2). The gut and upper respiratory tract (URT) microbiota harbor a dynamic and complex population of microorganisms and have strong interaction with host immune system homeostasis. However, our knowledge about microbiota and its association with SARS‐CoV‐2 is still limited. We aimed to systematically review the effects of gut microbiota on the SARS‐CoV‐2 infection and its severity and the impact that SARS‐CoV‐2 could have on the gut microbiota. Methods We searched the keywords in the online databases of Web of Science, Scopus, PubMed, and Cochrane on December 31, 2021. After duplicate removal, we performed the screening process in two stages; title/abstract and then full‐text screening. The data of the eligible studies were extracted into a pre‐designed word table. This study adhered to the PRISMA checklist and Newcastle−Ottawa Scale Bias Assessment tool. Results Sixty‐three publications were included in this review. Our study shows that among COVID‐19 patients, particularly moderate to severe cases, the gut and lung microbiota was different compared to healthy individuals. In addition, the severity, and viral load of COVID‐19 disease would probably also be influenced by the gut, and lung microbiota's composition. Conclusion Our study concludes that there was a significant difference in the composition of the URT, and gut microbiota in COVID‐19 patients compared to the general healthy individuals, with an increase in opportunistic pathogens. Further, research is needed to investigate the probable bidirectional association of COVID‐19 and human microbiome.

Introduction: Rare serious complications have been documented after COVID-19 vaccination as clinical research proceeded and new target populations, such as children and ‎pregnant women, were included. In this study, we attempted to review the literature relevant to ‎pregnancy complications and maternal outcomes of COVID-19 immunization in pregnant women. ‎ Methods: We searched the databases of PubMed, Scopus, Cochrane, and Web of Science on 31 August 2022. The records were downloaded and underwent a two-step screening; 1) title/abstract and then 2) full-text screening to identify the eligible studies. We included English original studies that evaluated the adverse effects of COVID-19 vaccines during pregnancy. Information such as the type of ‎study, geographical location, type of vaccine injected, gestational age, maternal underlying diseases, and ‎complications following the vaccination were extracted into pre-designed tables. Results: According to the findings of included studies, in most of them vaccination had a positive impact and no negative effects were observed. Also, no medical history was reported in 11 articles, and pregnant women had no underlying diseases. Some serious adverse events were reported after ‎vaccination, including miscarriage, paresthesia, uterine contraction, vaginal bleeding, preterm birth, major ‎congenital anomalies, intrauterine growth restriction, and seizure. ‎ Conclusion: Because of limited data availability and the cross-sectional design of most studies, we could neither infer ‎causation between vaccines and incidence of adverse effects nor comment with certainty about any ‎possible adverse outcome of COVID-19 vaccines in vaccinated pregnant women. Consequently, more longitudinal and experimental studies are needed to define the exact adverse effects of COVID-19 vaccines in pregnant women.

Introduction: Controversies existed regarding the duration of COVID-19 vaccines’ protection and whether receiving the usual vaccine doses would be sufficient for long-term immunity. Therefore, we aimed to systematically review the studies regarding the COVID-19 vaccines’ protection three months after getting fully vaccinated and assess the need for vaccine booster doses. Methods: The relevant literature was searched using a combination of keywords on the online databases of PubMed, Scopus, Web of Science, and Cochrane on September 17th, 2021. The records were downloaded and the duplicates were removed. Then, the records were evaluated in a two-step process, consisting of title/abstract and full-text screening processes, and the eligible records were selected for the qualitative synthesis. We only included original studies that evaluated the efficacy and immunity of COVID-19 vaccines three months after full vaccination. This review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement to ensure the reliability of results. Results: Out of the 797 retrieved records, 12 studies were included, 10 on mRNA-based vaccines and two on inactivated vaccines. The majority of included studies observed acceptable antibody titers in most of the participants even after 6 months; however,it appeared that the titers could also decrease in a considerable portion of people. Due to the reduction in antibody titers and vaccine protection, several studies suggested administering the booster dose, especially for older patients and those with underlying conditions, such as patients with immunodeficiencies. Conclusion: Studies indicated that vaccine immunity decreases over time, making people more susceptible to contracting the disease. Besides, new variants are emerging, and the omicron variant is continuing to spread and escape from the immune system, indicating the importance of a booster dose.