Search Results (338)

Background: Host genetic factors significantly influence individual susceptibility to severe COVID-19, potentially explaining the observed disparities in clinical outcomes across populations. One of the key effectors in innate immunity and antiviral defense is the CD209 gene. This study explored the potential correlation of the CD209 gene SNP rs2287886 with diverse COVID-19 patient outcomes. Materials and Methods: A total of 176 patients (87 in the moderate group and 89 in the severe/critical/death group) were included in the study. Genotyping of patients was performed using the qPCR methodology, through the TAQMAN system. The results were analyzed adopting a significance level of p < 0.05. Results: The GG genotype (compared to AG + AA) and the G allele (compared to the A allele) of the rs2287886 SNP were significantly associated with an increased severity of COVID-19 (p = 0.0005 and p < 0.0001, respectively). The G allele was more frequent in individuals with more severe clinical outcomes (49.43% vs. 25.28%). Furthermore, expression quantitative trait loci (eQTL) analysis indicated that the GG genotype of rs2287886 is associated with higher CD209 gene expression. Furthermore, the observed interaction analysis suggests that the interactions between CD209 and its associated proteins may play a role in modulating the immune response. Conclusions: Our findings suggest that Brazilian patients homozygous for the GG genotype of the rs2287886 polymorphism in the CD209 gene may be at increased risk of severe COVID-19 in the Brazilian population and may act as a potential prognostic marker of disease severity. Full article

(1) Background: COVID-19 sepsis, marked by hyperinflammation and cardiac injury, poses significant challenges in high-comorbidity populations. This prospective cohort study evaluates the prognostic value of IL-6, troponin, NT-proBNP, and radiological findings for mortality and unfavorable outcomes in a post-2022 Eastern European cohort. (2) Methods: At “Victor Babes” Hospital, Timisoara, Romania (September 2022–December 2024), 207 adults with COVID-19 sepsis (Sepsis-3 criteria) were enrolled. Baseline IL-6, troponin, NT-proBNP, CRP, PCT, D-dimers, and chest CT lung involvement were measured. Unfavorable outcomes (in-hospital death, ICU transfer, mechanical ventilation, or vasopressor use) were analyzed using logistic and linear regression. (3) Results: Among 207 patients (mean age: 68.7 years, 54.1% male), 52 (25.1%) experienced unfavorable outcomes. Multivariable analysis identified IL-6 (OR 1.016 per pg/mL, p = 0.013), troponin (OR 1.013 per ng/L, p = 0.017), NT-proBNP (OR 1.009 per pg/mL, p = 0.049), >50% lung involvement (OR 1.835, p = 0.011), unvaccinated status (OR 2.312, p = 0.002), and higher BMI (OR 1.112 per kg/m², p = 0.005) as independent predictors of unfavorable outcomes. Tocilizumab use (n = 12) was associated with reduced mortality (p = 0.041). IL-6 (cut-off 39.0 pg/mL, AUC = 0.91) and troponin (cut-off = 111.3 ng/L, AUC = 0.88) showed strong predictive accuracy. (4) Conclusions: Elevated IL-6, troponin, NT-proBNP, severe lung involvement, unvaccinated status, and higher BMI predict adverse outcomes in COVID-19 sepsis. Tocilizumab may offer survival benefits, warranting larger trials. These findings support targeted risk stratification in high-comorbidity populations. Full article

Background: Long COVID can persist for years, but little is known about its prevalence in relation to the number of infections. This study examines the prevalence of long COVID in association with the number of infections and vaccination status. Methods: We analyzed anonymized data on long COVID cases, thrombotic events and polypharmacy from March 2020, provided by the Data Analysis Control Department for the population assigned to the CST (192,651 at March 2025). Additionally, we analyzed responses to a long COVID symptom-specific survey distributed in March 2024 to individuals aged 18 to 75 years from the CST population diagnosed with COVID-19 as of December 2023 (n = 43,398; 3227 respondents). Symptomatic patients suspected of having long COVID underwent blood tests to exclude alternative diagnoses. Results: The overall detected prevalence of long COVID was 2.4‰, with higher frequency among women aged 30–59 years (p < 0.001). The survey, combined with specific blood tests, improved detection rates by 26.3%. Long COVID prevalence was 3–10 times higher in individuals with three or more infections than in those with only one recorded infection (based on survey/CST data, respectively). The absolute number of thrombotic events among individuals aged >60 doubled from 2020 to 2024, occurring in both vaccinated and unvaccinated individuals, as well as in those with or without prior documented COVID-19 infection, including in patients without chronic treatments. Conclusions: We found a link between SARS-CoV-2 reinfection and long COVID, and a post-pandemic rise in thrombotic events across all populations, regardless of vaccination or prior infection. Findings support continued COVID-19 diagnosis in suspected cases and mask use by healthcare workers treating respiratory patients. Full article

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) raced around the world across different populations; there needs to be a consolidated effort to understand the divergence of the epidemiology of SARS-CoV-2. Population-based epidemiological characteristics studies measure the extent of SARS-CoV-2 infection in a country. The current research study was designed to report epidemiological data from Pakistan. For this purpose, 246 SARS-CoV-2-infected patients were included in the study. For SARS-CoV-2 confirmation, viral samples were collected from all the study participants; SARS-CoV-2 infection was confirmed by viral nucleic acid detection using a nucleic acid detection kit. After SARS-CoV-2 confirmation, all the study participants were interviewed for epidemiological data through a detailed questionnaire. The study results showed that the disease ratio was higher between 30 and 59 years (51.21%) of age. The male ratio (55.28%) was higher compared to the female ratio (44.71%). The patients’ illiteracy and low socioeconomic status were 32.52% and 59.75%, respectively. The majority of the patients (97.56%) had cough, smell or taste disturbance (79.67%), or fever (76.42%), and 70.73% had fatigue. For comorbidities, a higher ratio was observed for diabetes (38.61%), hypertension (36.17%), and respiratory disease (16.26%). The vaccination status analysis revealed that 51.21% of patients had not received routine immunizations, and 65.5% were un-vaccinated against SARS-CoV-2. Notably, not a single patient was vaccinated for influenza vaccine. The current research study concluded that SARS-CoV-2 was more prevalent in individuals who were middle aged, male, and had low socio-economic status. The most common symptoms were cough, smell or taste disturbance, and fever. The patients’ vaccination status highlights a critical gap in preventive healthcare and shows the need to strengthen vaccination awareness and accessibility in the population to reduce vulnerability to future outbreaks. Future research should focus on investigating the impact of COVID-19 outcomes on comorbidities such as diabetes and hypertension. Full article

Objectives: The aim of the present study was to better understand the antibody concentrations in healthcare workers (HCWs) from a hospital in Mexico City with a high density of COVID-19 patients. Methods: Up to 243 HCWs were recruited in 2020 and 2022 and were sorted into three groups: hybrid immunity (HI, natural infection plus vaccination), vaccine-induced immunity (VI), and unvaccinated but RT-qPCR negative at the beginning of the pandemic (UV). Peripheral blood and nasopharyngeal swab samples were obtained; additionally, saliva samples were obtained from the UV group. The titers of IgG, IgM, and IgA against the SARS-CoV-2 receptor-binding domain (RBD) and nucleocapsid (NCP) proteins were assessed using an in-house ELISA, and positivity to the virus was determined via RT-qPCR. Results: Most HI and VI participants were positive for serum anti-RBD IgG (92.8% and 100%, respectively), while 26.6% (for HI) and 19% (for VI) were positive for anti-NCP IgG. Regarding serum anti-RBD IgA, the VI and HI groups had positive rates of 87.3% and 66%, respectively. In contrast, the UV group showed a rate of 5.7% but the positivity for IgA in saliva was higher (52% for RBD and 35% for NCP). In addition, the highest antibody titers were obtained for anti-RBD IgG and IgA in the HI and VI groups, respectively. In saliva, the IgA antibody titer was higher for the RBD antigen (1:1280). Conclusions: These results strengthen our understanding of antibody concentrations in HCWs during two critical years of the pandemic in a general hospital with many COVID-19 patients. Full article

Urine-based immunoassay is a non-invasive method with demonstrated utility in detecting anti-SARS-CoV-2 antibodies in unvaccinated patients with COVID-19. To evaluate urine’s potential for serological surveys in a real-world setting, SARS-CoV-2 serology was performed on urine samples from vaccinated individuals, both with and without prior confirmed COVID-19. (1) Methods: An in-house indirect ELISA was used to measure antibodies against recombinant spike (S) and nucleocapsid (N) proteins of SARS-CoV-2 in urine and paired serum from 149 individuals vaccinated with Janssen AD26.COV2.S, an S protein-based COVID-19 vaccine. (2) Results: Anti-S and anti-N levels were higher in the urine and serum of participants with confirmed prior COVID-19 compared to those without prior infection. Urinary anti-S effectively distinguished vaccinated individuals with (AUC = 0.96) and without (AUC = 0.88) prior infection from negative controls (non-vaccinated, non-previously infected individuals) (p < 0.0001). Among vaccinated participants, urinary anti-S and anti-N identified prior infection, with AUC values of 0.73 (p < 0.0001) and 0.60 (p = 0.03), respectively, being recorded. (3) Conclusions: Findings indicate that urinary anti-SARS-CoV-2 antibodies reflect AD26.COV2.S vaccination and previous COVID-19. To further advance the methodology, studies with larger sample sizes and a greater diversity of COVID-19 vaccines are required. Full article

Background/Objectives: Obesity is a major modifier of COVID-19 outcomes, contributing to increased disease severity and complications. This study aimed to assess the impact of obesity on clinical severity, pulmonary involvement, and in-hospital mortality among COVID-19 patients and to identify independent predictors of severe disease. Methods: We conducted a retrospective cohort study of 3005 hospitalized adults with RT-PCR-confirmed COVID-19 between 1 January 2020 and 1 March 2023. Patients were stratified by obesity status (body mass index (BMI) ≥ 30 kg/m²). Clinical, comorbidity, imaging, and laboratory data, as well as vaccination status (vaccinated or unvaccinated), were collected. Multivariate regression and gradient boosting models were used to identify predictors of severe outcomes. Effect estimates are expressed as relative risks (RRs) with 95% confidence intervals (CIs). Results: Obese patients (n = 894) showed significantly higher rates of severe COVID-19 (31.7% vs. 22.4%, p < 0.001) and more extensive lung damage (>50% involvement: 27.9% vs. 22.0%, p < 0.001), with lower admission SpO₂ (92.1 ± 4.0% vs. 94.2 ± 3.2%, p < 0.001). Hypoxemia (SpO₂ < 90%) was more frequent in obese individuals. The relative risk (RR) for severe disease was 1.41 (95% CI 1.25–1.60), and for >50% lung involvement, it was 1.27 (95% CI 1.11–1.45). Age > 65 years was the strongest predictor of mortality, particularly in non-obese patients. Gradient boosting models outperformed logistic regression (AUC = 0.92 vs. 0.87). Conclusions: Obesity independently predicts severe COVID-19 and pulmonary impairment. These findings support obesity-based risk stratification for clinical management and public health interventions. Full article

Background and Aims: The majority of individuals with COVID-19 developed acute symptoms. Post-COVID-19 syndrome refers to the signs and symptoms of COVID-19 that persist for more than 12 weeks. The present study was conducted to estimate the prevalence and risk factors for post-COVID-19 syndrome in the Omani population. Methods: This is a cross-sectional study that was conducted at the University Hospital Center (UHC). All patients diagnosed with COVID-19 (through polymerase chain reaction PCR testing) between March 2020 and March 2022 were included. Eligible participants were interviewed through a phone call, informed about the study procedure, and invited to participate in the study. Results: The study enrolled 265 COVID-19 patients, of whom 156 (59.2%) were females and 204 (77.3%) had been vaccinated. The overall prevalence of post-COVID-19 syndrome was 48.5%. The most common symptom was fatigue (71, 26.9%), followed by joint pain (44, 16.7%). The other symptoms included loss of taste/smell (34, 12.9%), cough (32, 12.1%), palpitation (25, 9.5%), and hair loss (27, 10.2%). Unvaccinated patients showed a higher incidence of fatigue (p = 0.03) and loss of smell/taste (p = 0.01) on univariate analysis. Females were at high risk for the development of various symptoms, including fatigue, muscular pain, breathing difficulty, cough, chest pain, palpitation, headache, and hair loss. Multivariate analysis showed that female gender is a significant independent predictor (odds ratio: 3.1; p = 0.00) for the development of post-COVID-19 syndrome. Conclusions: The prevalence of post-COVID-19 syndrome among the Omani population was high, highlighting the need for targeted interventions to manage long-term symptoms in vulnerable groups. Full article

COVID-19 vaccines have revolutionized prevention and clinical management by reducing disease severity and mortality. However, their long-term impact on hospitalization is unclear. This retrospective study assessed whether vaccination status, timing, and number of vaccine doses influence the risk of hospitalization and COVID-19 pneumonia in a large cohort in Italy, several years after initial vaccine rollout. From 1 October 2023, to 2 February 2024, at Humanitas Research Hospital (Milan) and two affiliates, we recorded age, sex, comorbidities, vaccination status (number of doses and time since last dose), admission type (urgent vs. elective), and pneumonia diagnosis. Baseline health was quantified by the Charlson Comorbidity Index. Among 16,034 admissions (14,874 patients), vaccination data were available for 5743 cases: 40.8% were in the emergency setting and 59.2% were elective. Patients presented with pneumonia in 6.8% of cases. Laboratory results confirmed COVID-19 pneumonia occurred in 43.7% of pneumonia cases, with a 16.9% mortality. Patients with no vaccine dose had a higher proportion of COVID-19 pneumonia, while COVID-19 pneumonia rates were lower in individuals who had received more vaccine doses. There were no significant differences in COVID-19 pneumonia risk by timing of last vaccination. Moreover, hospitalized unvaccinated patients had overall more frequent emergency admissions (57.3%), while patients with three or more doses had about a ~40% emergency admission rate. COVID-19 positivity during hospitalization was highest in unvaccinated patients (90.7%) and declined with vaccination status. Vaccinated patients, especially those with multiple doses, had significantly lower COVID-19 pneumonia rates and emergency admissions. These findings suggest a possible protective effect of vaccination in modifying the clinical presentation and severity of illness among those who are hospitalized and support continued vaccination efforts for high-risk groups to reduce severe adverse outcomes. Full article

Background: Osteogenesis imperfecta (OI) is a rare genetic connective tissue disorder characterized by bone fragility, most often caused by pathogenic variants in type I collagen genes. In this context, we aimed to describe the clinical and epidemiological characteristics of patients with OI who were hospitalized for coronavirus disease (COVID)-19 in Brazil between 2020 and 2024. Methods: We conducted a retrospective descriptive analysis using data from the Brazilian Unified Health System (SUS, which stands for the Portuguese Sistema Único de Saúde) through the Open-Data-SUS platform. Patients with a confirmed diagnosis of OI and hospitalization due to COVID-19 were included. Descriptive statistical analysis was performed to evaluate demographic, clinical, and outcome-related variables. We included all hospitalized COVID-19 cases with a confirmed diagnosis of OI between 2020 and 2024. Results: Thirteen hospitalized patients with OI and COVID-19 were identified. Most were adults (9; 69.2%), male (7; 53.8%), self-identified as White (9; 69.2%), and all were residents of urban areas (13; 100.0%). The most frequent symptoms were fever (10; 76.9%), cough (9; 69.2%), oxygen desaturation (9; 69.2%), dyspnea (8; 61.5%), and respiratory distress (7; 53.8%). Two patients had heart disease, one had chronic lung disease, and one was obese. As for vaccination status, five patients (38.5%) had been vaccinated against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Four patients (30.8%) required admission to an intensive care unit (ICU), and six (46.2%) required noninvasive ventilatory support. Among those admitted to the ICU, only two required invasive mechanical ventilation. The clinical outcome was death in two cases (15.4%). Both patients were male, White, and had not been vaccinated against SARS-CoV-2. One was 47 years old, was not admitted to the ICU, but required noninvasive ventilation. Despite the underlying condition most patients had favorable outcomes, consistent with an international report. Conclusions: This is the first report to describe the clinical and epidemiological profile of patients with OI hospitalized for COVID-19 in Brazil, providing initial insights into how a rare bone disorder intersects with an acute respiratory infection. The generally favorable outcomes observed—despite the underlying skeletal fragility—suggest that individuals with OI are not necessarily at disproportionate risk of severe COVID-19, particularly when appropriately monitored. The occurrence of deaths only among unvaccinated patients underscores the critical role of SARS-CoV-2 vaccination in this population. Although pharmacological treatment data were unavailable, the potential protective effects of bisphosphonates and vitamin D merit further exploration. These findings support the need for early preventive strategies, systematic vaccination efforts, and dedicated clinical protocols for rare disease populations during infectious disease outbreaks. Full article

Background/Objectives: Neutralizing autoantibodies against type I interferons, particularly interferon-alpha (IFN-α), have been implicated in severe COVID-19 outcomes. This study investigated the prevalence and functional significance of anti-IFN-α autoantibodies (AAbs) in hospitalized unvaccinated COVID-19 patients and their association with COVID-19 disease severity. Methods: We retrospectively analyzed serum samples from 122 hospitalized COVID-19 patients (asymptomatic/mild: n = 69, moderate: n = 35, severe/critical: n = 18) and 32 healthy uninfected controls. Anti-IFN-α AAbs were quantified using a commercial enzyme-linked immunosorbent assay (ELISA) kit, with functional neutralization assessed via competitive ELISA and STAT1 phosphorylation inhibition. Statistical comparisons were performed using one-way ANOVA for parametric data and the Kruskal–Wallis test for non-parametric variables. Results: Anti-IFN-α AAbs were detected in 24.6% of COVID-19 patients, with all clinical subgroups showing significantly higher titers compared to healthy controls (p < 0.05). Although no significant differences in anti-IFN-α AAb levels were found between mild, moderate, and severe cases, patients with severe or critical COVID-19 had markedly higher mean titers (10,511.3 ng/mL) compared to non-severe (mild + moderate) cases (375.2 ng/mL, p < 0.001). Strongly neutralizing anti-IFN-α AAbs, with high titers (>20,000 ng/mL) and the ability to inhibit STAT1 phosphorylation, were identified in three severe COVID-19 cases. Anti-IFN-α AAb levels correlated positively with CRP (r = 0.80, p < 0.0001), LDH (r = 0.80, p = 0.001), and neutrophil count (r = 0.52, p = 0.003), and negatively with lymphocyte count (r = −0.59, p = 0.0006). Conclusions: Elevated and functionally neutralizing anti-IFN-α AAbs were associated with severe COVID-19. These findings support their role as a risk factor for poor outcomes and emphasize the importance of early COVID-19 vaccination. Screening may help identify high-risk individuals, particularly those unvaccinated or with immune vulnerabilities. Full article

Background: Although COVID-19 vaccination has been effective in reducing severe illness and mortality, its differential clinical behavior in vaccinated and unvaccinated individuals during the early stages of the pandemic—especially in settings with partial coverage and real-world conditions—remains insufficiently characterized. Objective: To assess differences in clinical presentation, comorbidity prevalence, hospitalization, and mortality between vaccinated and unvaccinated patients diagnosed with SARS-CoV-2 during the early phase of the pandemic. Methods: An analytical cross-sectional study was conducted using 4625 electronic medical records of patients diagnosed with COVID-19 in Guerrero, Mexico, between 1 January and 31 December 2021. Variables included vaccination status, age, sex, comorbidities, symptom severity, clinical outcomes, and mortality. Statistical analyses involved chi-square tests, logistic regression for hospitalization probability, and Cox proportional hazards models for mortality risk. Results: Of the patients analyzed, 31.45% had received at least one vaccine dose. Fever, headache, cough, and anosmia were more frequent among vaccinated individuals (p < 0.001). Prostration and chest pain were strongly associated with hospitalization in both groups. In unvaccinated patients, smoking (OR = 4.75), obesity (OR = 3.85), and hypertension (OR = 2.94) increased hospitalization risk. Among vaccinated patients, diabetes mellitus (OR = 3.62) and hypertension (OR = 2.88) were key predictors. Vaccination was significantly associated with lower odds of hospitalization (OR = 0.38; 95% CI: 0.26–0.55) and reduced mortality risk (HR = 0.24; 95% CI: 0.08–0.71). Conclusions: Vaccination status was a significant protective factor for both hospitalization and mortality; however, clinical symptoms and comorbidity-related risks varied, highlighting the need for individualized patient management strategies. Full article

Background/Objectives: Tick-borne encephalitis (TBE) is a notifiable disease in Poland, with the highest incidence in the northeastern region. Although vaccination is highly effective, breakthrough infections occasionally occur. This study aimed to describe the clinical features of vaccinated and unvaccinated TBE cases, assess long-term hospitalization trends, and estimate vaccine effectiveness (VE) in a highly endemic region. Methods: We retrospectively analyzed 1518 laboratory-confirmed TBE cases hospitalized at the University Clinical Hospital in Białystok, Poland, from 1988 to 2020. Clinical and cerebrospinal fluid (CSF) parameters were compared between vaccinated and unvaccinated individuals. Vaccine effectiveness was estimated using the screening method, based on aggregated regional vaccine uptake data from 1999 to 2020. Results: Among all cases, 13 (0.9%) occurred in individuals who had received at least one dose of vaccine, including 4 who had completed the full primary vaccination schedule. Hospitalized vaccinated patients showed similar demographic and clinical characteristics compared to unvaccinated patients, though CSF findings suggested an earlier and more dynamic immune response. Seasonal analysis revealed a sustained increase in TBE hospitalizations and a possible extension of the transmission season into late summer and autumn. Estimated VE was 94.4% (95% CI 85.2–97.9%), though this should be interpreted with caution due to the small number of vaccinated cases and assumptions regarding population-level coverage. Conclusions: This study provides detailed clinical data on breakthrough TBE cases and long-term epidemiological insights from an endemic region in Poland. While vaccine effectiveness appears high, low uptake remains a public health concern. These findings underscore the need for improved vaccination coverage and ongoing surveillance to monitor evolving transmission patterns. Full article

Background: Influenza B usually causes mild illness in children. Severe and fatal cases can occur when complicated by secondary Staphylococcus aureus (S. aureus) pneumonia, including community-acquired methicillin-resistant Staphylococcus aureus (MRSA). We present a rare, rapidly progressive fatal case in an adolescent with no known medical history to highlight diagnostic and therapeutic pitfalls. Case Presentation: A 16-year-old boy with no known underlying conditions (unvaccinated for influenza) presented critically ill at “Sf. Ioan” Clinical Emergency Pediatric Hospital in Galați after one week of high fever and cough. He was in respiratory failure with septic shock, requiring immediate intubation and vasopressors. Chest X-ray (CXR) showed diffuse bilateral infiltrates (acute respiratory distress syndrome, ARDS). Initial laboratory tests revealed leukopenia, severe thrombocytopenia, disseminated intravascular coagulation (DIC), rhabdomyolysis, and acute kidney injury (AKI). Reverse transcription polymerase chain reaction (RT-PCR) confirmed influenza B, and blood cultures grew MRSA. Despite maximal intensive care, including mechanical ventilation, antibiotics (escalated for MRSA), antiviral therapy, and cytokine hemoadsorption therapy, the patient developed refractory multi-organ failure and died on hospital day 6. Autopsy revealed bilateral necrotizing pneumonia (NP) without radiographic cavitation, underscoring the diagnostic challenge. Discussion: The initial chest radiography showed diffuse bilateral pulmonary infiltrates, predominantly in the lower zones, with an ill-defined, patchy, and confluent appearance. Such appearance, in our case, was more suggestive of rapid progressive NP caused by MRSA rather than the typical pneumococcal one. This is one of the few reported cases of influenza B–MRSA coinfection with fulminant rhabdomyolysis and autopsy-confirmed necrosis. Our fulminant case illustrates the synergistic virulence of influenza and MRSA. Toxin-producing MRSA strains can cause NP and a “cytokine storm,” causing capillary leak, ARDS, shock, and DIC. Once multi-organ failure ensues, the prognosis is grim despite aggressive care. The absence of early radiographic necrosis and delayed anti-MRSA therapy (initiated after culture results) likely contributed to the poor outcome. Conclusions: Influenza B–MRSA co-infection, though rare, demands urgent empiric anti-MRSA therapy in severe influenza cases with leukopenia or shock, even without radiographic necrosis. This fatal outcome underscores the dual imperative of influenza vaccination and early, aggressive dual-pathogen targeting in high-risk presentations. Full article

Background: Childhood cancer survivors (CCSs) often experience impaired humoral immunity because of cancer treatments that increase their susceptibility to vaccine-preventable diseases. This study aimed to assess the seroprevalence of tetanus and rubella antibodies in CCSs compared to healthy, age-matched controls. Additionally, we explored the impact of cancer treatments on vaccine-induced immunity, examined the extent of revaccination after treatment completion, and evaluated the effectiveness of revaccination on seroprevalence. Methods: This retrospective study included 180 CCSs previously treated at Astrid Lindgren Children’s Hospital, Stockholm, between March 2019 and January 2023. Patient data were retrieved from electronic medical records. Seroprevalence data for rubella and tetanus antibodies in the 15–19-year age group were also obtained from a national seroprevalence study conducted by the Public Health Agency of Sweden. Results: CCSs exhibited significantly lower seroprevalence for both tetanus (77.7% vs. 92.7%) and rubella (79.1% vs. 97.5%) compared to age-matched controls. Revaccination with DTP-containing vaccines was more frequently administered than with the MMR vaccine. Tetanus and rubella seroprevalence were the lowest in children who had received intense chemotherapy. Among those who were revaccinated with the DTP vaccine after intensive treatment, 81 out of 98 (82.6%) had tetanus IgG levels above the threshold, compared to 24 out of 48 (50%) unvaccinated CCSs. In contrast, among those revaccinated with MMR, 57 out of 73 (78.1%) had positive rubella IgG, compared to 53 out of 73 (72.6%) unvaccinated CCSs with rubella IgG levels above the cut-off. Conclusions: Our findings highlight that vaccines are underutilized in CCSs with a notable gap in immunity, particularly among those who have undergone intensive treatments. Unexpectedly, MMR revaccination did not significantly affect rubella immunity. Given the increasing number of CCSs, it is essential to better understand how to effectively restore vaccine immunity in this population. Full article