COVID-19 Vaccine Research Articles

Background: Children with congenital heart disease (CHD) represent a vulnerable population with heightened susceptibility to respiratory infections. However, comprehensive data characterizing COVID-19 outcomes, vaccination benefits, and healthcare disparities in pediatric CHD patients remain limited. This study synthesizes multicenter evidence to evaluate clinical outcomes, vaccination effectiveness, and healthcare inequities affecting pediatric CHD patients during the COVID-19 pandemic. Methods: We conducted a comprehensive analysis integrating data from four primary sources: (1) an international editorial review examining pandemic impacts on CHD care delivery, (2) analysis of national hospitalization data comparing CHD patients with non-CHD pediatric counterparts, (3) a large-scale population-based study evaluating vaccination outcomes in CHD patients, and (4) a multicenter pediatric COVID-19 case series including complex CHD subgroups. Clinical outcomes, vaccination effectiveness, and healthcare access disparities in the Low and Middle Income Countries (LMIC) were systematically analyzed. Results: Analysis of pediatric CHD patients (median age 3 years) revealed significantly higher COVID-19 complications versus non-CHD controls: cardiovascular (tachyarrhythmias aOR 4.1, 95%CI 2.9-5.8), respiratory (mechanical ventilation RR 3.2, 2.1-4.9), and systemic (acute kidney injury aOR 3.4, 2.2-5.3; all p<0.001). While mortality remained low (CHD 1.2% vs non-CHD 0.8%, p=0.21), children <3 years accounted for 40% of cases and 78% of critical illnesses (p<0.001), with 70% showing bilateral lung involvement. Complex CHD anatomy conferred 4.3-fold higher ICU risk (95%CI 2.7-6.8). Vaccination reduced hospitalizations by 87% (aOR 0.13, 0.08-0.22), though disparities persisted with 68% of LMIC patients experiencing delayed cardiac surgeries. Conclusions: While most pediatric COVID-19 cases demonstrate favorable outcomes, children with CHD—particularly infants and those with complex cardiac anatomy—face substantially increased complication risks. COVID-19 vaccination provides significant protection for CHD patients but does not eliminate outcome disparities compared to healthy children. The pandemic revealed critical inequities in CHD care access, highlighting the urgent need for targeted interventions to protect high-risk pediatric populations and address healthcare disparities in resource-limited regions.

Introduction/Background: The COVID-19 vaccines has been pivotal in controlling SARS-CoV-2 transmission and reducing hospitalization and mortality. Authorized vaccines, including mRNA-based and adenoviral vector platforms, have demonstrated strong safety and efficacy profiles. However, post-marketing surveillance has identified rare cases of vaccine-associated myocarditis and pericarditis, predominantly among young males following mRNA vaccines. Understanding these occurrences is essential to inform risk-benefit analyses and guide clinical management. Research Questions/Hypothesis: What is the clinical presentation and outcome of myocarditis and related cardiologic manifestations following COVID-19 vaccination? Goals/Aims: This review aims to evaluate the frequency, clinical characteristics, diagnostic findings, and short-term outcomes of myocarditis, pericarditis, and myopericarditis following COVID-19 immunization. Methods/Approach: A systematic search was conducted across PubMed, PMC, Embase, Google Scholar, and the VAERS database to identify relevant literature between March 2020 and April 2022. A total of 98 studies were screened, and 75 met the inclusion criteria, including 47 primary studies (case reports/series) detailing 103 individual cases. English-language studies involving adverse cardiac events temporally related to COVID-19 vaccination in the U.S. were included. Results/Data: Of the 103 reported cases, myocarditis was most prevalent (n=88, 85.4%), followed by myopericarditis (n=10) and pericarditis (n=5). Most cases (n=90, 87.4%) involved male patients, particularly aged 16–30. The BNT162b2 (Pfizer) vaccine was associated with the highest number of cases (n=67), followed by mRNA1273 (Moderna, n=29), and Ad26.COV2.S (J&J, n=4). The average symptom onset was 3.5 days post-vaccination, with chest pain (90.9%) being the most common symptom. Elevated troponin (89.7%), ECG abnormalities (80.6%), and cardiac MRI findings consistent with myocarditis (70.4%) were frequently reported. Clinical outcomes were favorable in 93.1% of cases, with symptom resolution and discharge. Five deaths were reported.

Background: Granulomatosis with polyangiitis (GPA) is a rare ANCA-associated vasculitis characterized by necrotizing granulomatous inflammation and small- to medium-vessel vasculitis. The COVID-19 pandemic has raised interest in its potential to trigger autoimmune diseases like GPA. This retrospective study investigates changes in GPA frequency, clinical features, and serological patterns before and after the COVID-19 pandemic. Methods: This retrospective study analyzed 72 patients with granulomatosis with polyangiitis (GPA) at one of the most referral hospitals (2016–2024), divided into pre-COVID (n = 27) and post-COVID (n = 45). Demographic, clinical, radiological, and laboratory data were collected. Pre and post-COVID groups were compared using t-tests and chi-square tests. Firth’s logistic regression identified predictors of post-COVID GPA, adjusting for age, sex, ANCA subtype, and clinical features. Results: A total of 72 patients with granulomatosis with polyangiitis (GPA) were analyzed, including 27 diagnosed pre-COVID-19 and 45 post-COVID-19. The post-COVID-19 cohort was significantly younger (mean age 37.75 ± 10.38 vs. 50.66 ± 12.76 years, P < 0.001) and showed increased prevalence of pulmonary ground-glass opacities (64.4% vs. 25.9%, P = 0.003), cutaneous manifestations (75.6% vs. 25.9%, P = 0.004), and ophthalmic involvement (44.4% vs. 11.1%, P = 0.007). Firth’s logistic regression identified younger age (OR = 0.89, 95% CI: 0.82–0.97, P = 0.008), male sex (OR = 1.94, 95% CI: 1.02–3.99, P = 0.044), pulmonary ground-glass opacities (OR = 5.71, 95% CI: 1.84–18.27, P = 0.002), and ophthalmic complications (OR = 3.27, 95% CI: 1.02–10.48, P = 0.047) as predictors of post-COVID-19 GPA. No association was found between COVID-19 vaccination and GPA onset or relapse (P = 0.429). Conclusion: This study reveals a higher frequency of granulomatosis with polyangiitis (GPA) and a younger age at onset post-COVID-19. Predictors of post-COVID-19 GPA included younger age, male sex, and pulmonary involvement. SARS-CoV-2 may trigger autoimmune activation, but no link with vaccination was found. GPA clinical features remained consistent, warranting ongoing monitoring and research into COVID-19’s autoimmune effects.

Background: COVID-19 and, more rarely, its mRNA vaccination have been associated with myocarditis, often with greater incidence and severity in males. Long-term outcomes, such as recovery of left ventricular ejection fraction (LVEF), particularly in context of sex differences, remain poorly understood. Hypothesis: We hypothesized that sex-based differences exist in LVEF recovery following COVID-19-related myocarditis. Methods: We conducted a retrospective cohort study of 85,376 COVID-19 patients (January 2020–January 2024) in the Mass General Brigham system. 1,193 had undergone a CMR and 259 had a myocardial biopsy. We included patients with either biopsy or CMR-confirmed myocarditis based on Lake Louise criteria (for acute cases) or clinically suspicious late gadolinium enhancement (LGE) patterns (for delayed imaging), excluding alternative causes (e.g., other viral infections, immunotherapy) and patients with amyloidosis or sarcoidosis. A total of 51 patients met our criteria and were categorized into: COVID-19 infection (acute: <14 days, delayed: ≥14 days) or vaccination. Patients were followed up to May 2025. Results: Among 51 patients (mean age 47±15, 26 female), 44 had infection-related myocarditis (26 acute, 18 delayed), 4 were vaccine-related, and 3 had recurrent myocarditis with infection and vaccination. Cases were followed for a minimum of 2 years and median of 4 years. LVEF reduction was seen in 24 patients (10 females; none vaccine-related; mean EF 34% ± 12%) with 15 (63%) making full recovery to baseline or LVEF > 50% within a median of 3 months. Most recovered patients received guideline-directed therapy, though some improved without it. Out of 9 without recovery, 8 were males and 6 had acute infection. 90% of females vs 42% of males had LVEF recovery, p=0.03. CMR revealed LGE in 94%, mostly in basal inferolateral region; T2 elevation in 22% and T1 in 27%. One biopsy confirmed fulminant necrotizing myocarditis. No deaths or transplants occurred. Conclusions: This multi-center study presents one of the largest cohorts of CMR- or biopsy-confirmed myocarditis associated with COVID-19 and is the first to demonstrate sex differences in LVEF recovery. Half of our patients experienced reduced LVEF, with 18% failing to recover, most of whom were males. No vaccine-associated cases led to reduced LVEF. Our findings highlight the prognostic value of sex and importance of long-term follow-up. Prospective studies are needed to confirm predictors of recovery.

Community Network-Driven COVID-19 Testing and Vaccination of Vulnerable Populations in the Central United States (C3) evaluates the use of Social Network Strategy (SNS) with educational messaging to improve COVID-19 testing and vaccination among people most impacted by the pandemic. We enrolled individuals with low-income who identify as Hispanic/Latino or a history of criminal legal involvement (CLI) through social network referral and randomized participants 1:1 to SNS vs. SNS plus messaging (SNS+), which included a self-affirmation activity and educational video. We assessed for COVID-19 testing and, among baseline unvaccinated participants, vaccination at 21days, and used mixed effects logistic regression to examine outcomes. Of 1328 participants (SNS+: 667, SNS: 661), 46.6% identified as Black/African American, 33.4% as Hispanic/Latino, and 43.8% reported history of CLI. Majority (66.3%) reported testing and, of unvaccinated participants, 11.9% reported vaccination at follow-up. There were no differences in testing (aOR 0.89, 95% CI 0.71, 1.11, P=.49) or vaccination (aOR 1.46, 95% CI 0.78, 2.76, P=.30) among participants who received SNS+ compared to SNS after adjusting for recruitment wave and clustering within sites and referral chains. Social network referral successfully engaged communities disproportionately impacted by COVID-19 in testing and vaccination. Compared to SNS alone, adding educational messaging did not increase testing or vaccination. Additional work is needed to implement SNS to increase vaccination rates among vulnerable populations.

BackgroundThe COVID-19 vaccine hesitancy continuum reflects an individual decision-making process regarding vaccination, ranging from fully willing to accept the vaccine to outright refusal. This study assessed COVID-19 vaccine hesitancy and compared the explanatory power of selected psycho-behavioral models for its variability among adults living in Southwest Ethiopia.MethodsA community-based cross-sectional study was conducted in Southwest Ethiopia from January 1 to 15, 2022. The calculated sample size was 879. A multistage sampling technique was used to select study participants. Data were collected using an interviewer-administered questionnaire comprising four sections: socio-demographic characteristics, COVID-19-related covariates, psycho-behavioral constructs, and a vaccine hesitancy scale. The data were entered into Epi-Data, and analysis was performed using Python in Jupyter Notebook. Descriptive statistics and hierarchical multiple linear regression were performed to compare the predictive ability of four psycho-behavioral models: the health belief model (perceived susceptibility, severity, benefit, barrier, and cues to actions); the theory of planned behavior (attitudes, subjective norms, behavioral control, and anticipated regret); five psychological antecedents (confidence, complacency, constraints, calculation, and collective responsibility); and vaccine conspiracy belief (conspiracy related to infection and the vaccine). Model comparison was done using adjusted R-squared and model selection criteria.ResultsThe mean age of the participants was 31.63 ± 8.28, and 365 (44.3%) of them were female. The mean score of the COVID-19 vaccine hesitancy continuum was 5.11 ± 2.41. Among the respondents, 91 (11%) were fully willing to accept the COVID-19 vaccine, while 97 (11.8%) were completely resistant. The remaining 624 (77.18%) participants were hesitant to make a decision about vaccination.The vaccine conspiracy belief demonstrated the most predictive ability (adjusted R2 = 0.43), followed by the 5C psychological antecedent (adjusted R2 = 0.36), the theory of planned behavior (adjusted R2 = 0.26), and the health belief model (adjusted R2 = 0.20).ConclusionCOVID-19 vaccine hesitancy in Ethiopia is most predicted by vaccine conspiracy belief. Therefore, public health intervention should focus on addressing misinformation and conspiracy narratives.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12889-025-24470-w.

Vaccine hesitancy (VH) among vaccinated individuals remains a relatively under investigated topic. This study contributes to fill this research gap by examining the social representations of COVID-19 vaccines among vaccinated Italian adults. Using a mixed-method approach, we analyzed data from 664 vaccinated Italian adults through hierarchical cluster analysis and similarity analysis. Results revealed distinct representational patterns between non-hesitant and slightly hesitant adopters despite their shared vaccination status. While safety emerged as a core element in both groups' representations, non-hesitant participants expressed a more positive affective-cognitive orientation anchored in scientific trust whilst slightly hesitant adopters exhibited persistent ambivalence, with emotional elements (particularly fear and anxiety) playing a prominent role. The findings challenged the assumption that VH reflects complete vaccine refusal and suggests the need for tailored public health communication strategies. The results indicate that interventions should consider VH levels and variability beyond the mere dichotomy hesitant-not hesitant. Recommendations are discussed.

Real-world studies on vaccine effectiveness may suffer from several biases, typically distorting their results. A previous article on the population of an Italian province, correcting the “immortal time bias”, showed worse results for the all-cause death of the vaccinated compared to the unvaccinated. This article highlights the “case counting window bias”, that considers the vaccine recipients “unvaccinated” usually for 14 days, a time interval reputed necessary to express the vaccine immune response. We aim to document this bias in an Italian region, calculating the daily death incidence for each age class of vaccinated and unvaccinated and checking their all-cause mortality difference within the considered time window. Indeed, in this window the two groups showed huge differences in all-cause deaths, that cannot be attributed only to COVID-19 deaths (in the absence of reasons to expect significant vaccine effects on non-COVID-19 deaths). In conclusion, analyzing the data of an Italian Region, we found evidence of the ‘case counting window bias’, which artificially increases the ‘unvaccinated’ mortality and reduces the mortality in the vaccinated.

Background: Infectious bronchitis virus (IBV) is a highly spreading, evolving virus that induces multiple manifestations, including respiratory, urinary, and reproductive symptoms, and presents a considerable risk to the Egyptian poultry sector. This study assessed various IBV vaccination protocols available in broiler populations comprising live attenuated vaccines such as IB Var II, 793/B (4/91), IB Primer, and H120 against the local novel IBV-GI-23.3 strain. Methods: Vaccines were administered to eight groups of SPF chicks at 1 day only or 1 + 14 days of age. Birds were challenged via the oculo-nasal route at 28 days of age using 106 EID50/0.2 mL/chick with the NewValley-1-EGYIBV-GI23.3-2023 local strain. Ciliostasis activity and the scores for histopathological lesions were evaluated at 7 days post-challenge (DPC). Virus shedding was monitored at 3, 5, and 7 DPC using the real-time RT-PCR method. Results: The ciliostasis test indicated that the vaccinated groups receiving the IB Primer + 4/91 vaccine regime at 1 day only or 1 + 14 days of age received the highest level of protection (65%, 68%, respectively). Similarly, administration of IB Primer + IB Var II at 1 + 14 days of age demonstrated substantial protection (63%). Conversely, administering the H120 + 4/91 vaccination protocol at days 1 and 14 resulted in a moderate level of protection (53%). Tracheal IBV shedding quantification and subsequent histopathological signs of trachea, proventriculus, bursa, and kidney degenerative changes were significantly lower in the vaccinated groups (especially the IB Primer + 4/91 vaccine regime at 1 day only or 1 + 14 days) than in the positive control groups. Conclusions: The heterologous combined IB Primer + 4/91 program demonstrated the most significant protective efficacy against the IBV field challenge strains compared with other vaccines in broiler chickens.

Adverse events associated with COVID-19 vaccination or diagnosis among pregnant and non-pregnant women in the United States, 2021-2022.

Belgium prioritized primary COVID-19 vaccination of persons aged 18-64 years with underlying health conditions over their same-aged peers, leading to an accelerated administration of a first dose of 35 days. We assessed this strategy's impact on hospital admissions, in comparison to alternative scenarios, using generalized causal inference techniques with a hierarchical Bayesian model. A solely age-based scenario showed a significant increase in hospital admissions of 254, while random-allocation and no-vaccination scenarios showed even higher increases (604 and 1998, respectively). These results emphasize the importance of prioritization strategies in a pandemic context and the benefits of COVID-19 vaccines in general.

Understanding the attitudes of unvaccinated COVID-19 patients hospitalized in Greece toward the 2024-2025 booster COVID-19 vaccine.

BNT162b2 XBB.1.5-Adapted Single Dose Vaccine Uptake and Effectiveness in Children Aged 5-17 Years Using Linked Claims and Vaccine Registries in California and Louisiana.

A web questionnaire-based study of institutional support and COVID-19 vaccination uptake in healthcare personnel in Japan.

Chronic conditions, disability, and COVID-19 testing and vaccination: A national Rapid Acceleration of Diagnostics-Underserved Populations analysis.

Vaccination is an effective response to the COVID-19 pandemic, but vaccine hesitancy is a major challenge. This study aims to explore the pooled prevalence and factors of COVID-19 vaccine hesitancy. We searched the studies published from January 2020 to December 2023 in PubMed, Web of Science, and Embase. The studies with complete start time of the study and national information were included in the generalised additive model to explore the factors affecting the COVID-19 vaccine hesitancy rate by calculating OR and 95%CI. A total of 629 studies were included. The pooled global hesitancy rates of COVID-19 vaccine were 34.6% (95% CI: 31.2%-38.1%) in vulnerable population and 33.2% (95% CI: 31.7%-34.8%) in general populations. The regression model showed that the hesitancy rate of COVID-19 vaccine was correlated with the duration of the epidemic, the monthly governmental stringency index, the monthly incidence and mortality of COVID-19, SDI, geographical location, and health status. Local governments should pay special attention to vaccination of vulnerable population and encourage vaccination to cope with the next possible wave of pandemic as incidence declines and restrictions are eased. The international community should timely provide vaccines for low economy countries.

Mechanistic modeling of lipid nanoparticle formation for the delivery of nucleic acid therapeutics.

This study estimated the potential public health and economic impacts of different COVID-19 vaccination strategies in Malaysia using an updated COVID-19 vaccine. A previously published Markov decision-tree model (2021-2022) was updated with the latest epidemiology data from Malaysia (October 2022-September 2023). This updated model was used to assess the outcomes of alternative vaccination strategies using the updated COVID-19 vaccine. Age-specific inputs were derived from Malaysian epidemiological data and published sources. The model projected health outcomes (cases, hospitalizations, and deaths) and economic outcomes (direct medical costs and productivity losses) across various age and risk categories. Vaccinating individuals aged 60 and above, as well as high-risk individuals aged 6months to 59years with vaccine coverage of 20%, was projected to prevent 91,824 infections, 1477 hospitalizations, and 53 deaths. The model estimated total savings of MYR 90.9 million in direct medical costs attributed to COVID-19 treatment and MYR 110.4 million in indirect costs attributed to COVID-19 illness. Expanding coverage among individuals aged 60 and above, as well as high-risk individuals of any age, to 50% could further increase the reduction in deaths, hospitalizations, infections, and costs by up to 150%. When considering recent updated epidemiology data and expected vaccination coverage, vaccination strategies appear to have a smaller impact, largely caused by the reduction in vaccine coverage. However, despite this, using an updated COVID-19 vaccine could still reduce the health and economic burden of COVID-19 in terms of cases, hospitalizations, deaths, direct medical costs, and indirect productivity losses in Malaysia, especially among high-risk populations and older adults.

Background: Addressing Missed Opportunities for Vaccination (MOV) contributes to increased vaccination rates in children, reinforcing the need to investigate and intervene in the related factors. Objective: To analyze factors associated with missed opportunities for vaccination in children under one year of age in a Brazilian capital. Methods: This was a cross-sectional, analytical study conducted in seven Basic Health Units in Teresina, Piauí, Brazil. A previously validated questionnaire was applied to parents or guardians of a sample of 316 children. Data were collected from March to June 2025. Multivariable Logistic Regression was performed, and results were expressed as Odds Ratios. Results: Among the children, 53.5% had at least one MOV. The associated factors were: parents with two or more children (95% CI: 1.06–2.96), false contraindications (95% CI: 1.29–8.73), inadequate assessment of vaccination cards by health professionals (95% CI: 1.78–29.00), vaccine shortages in health units (95% CI: 1.57–18.28), and refusal to open multidose vaccine vials (95% CI: 1.81–19.31). Receiving information about vaccination in the previous month was a protective factor against MOV (95% CI: 0.25–0.77). The vaccines most frequently contributing to MOV were BCG (15.8%) and the COVID-19 vaccine, with 15.5% for the first dose and 14.9% for the second. Conclusions: The high prevalence of MOV found in this study indicates weaknesses in the immunization process and suggests the need for implementing measures to interrupt the chain of causes leading to MOV, thereby contributing to the achievement of the objectives of the Brazilian National Immunization Program.

The mismatch between COVID-19 vaccination implementation and vulnerable population: Spatiotemporal analysis of neighborhood-level COVID-19 vaccination rates in San Diego, California