From messenger RNA to viral vectors and recombinant proteins: the evolution of vaccines against COVID-19 / Del ARN mensajero a los vectores virales y las proteínas recombinantes: la evolución de las vacunas contra COVID-19

Entre finales de 2019 y mediados de 2022, la pandemia de COVID-19 ha causado más de 600 millones de casos confirmados y al menos 6,5 millones de muertes, constituyendo la emergencia de salud pública más importante de las últimas décadas. En paralelo con el transcurso de la pandemia, ha tenido lugar una carrera sin precedentes por la obtención de vacunas eficaces para el control de la rápida dispersión del virus. Cuatro meses después del anuncio de la emergencia del SARS-CoV-2, agente de la pandemia, ya habían 115 "vacunas candidatas", cinco de ellas en fase de ensayos clínicos [1]. Al mismo tiempo, una gran revolución en la producción de vacunas estaba ocurriendo; nuevas tecnologías de producción de biológicos, más eficaces y más rápidas, llevaron al desarrollo de vacunas útiles en un tiempo increíblemente corto. Antes de la pandemia, el desarrollo de una nueva vacuna típicamente solía tomar entre cinco y diez años, pero en 2020, a menos de un año de haberse declarado la pandemia, ya se habían publicado ensayos clínicos que demostraban la eficacia de varias vacunas producidas mediante tecnologías novedosas [2]. Son numerosas las vacunas contra el SARS-CoV-2 que han sido autorizadas para su uso. A la fecha, más de 12 mil millones de dosis de vacunas han sido administradas en el mundo [3]. Se estima que tres dosis de vacunas pueden evitar hasta en un 94 % el riesgo de uso de ventilación mecánica y muerte [4], así mismo, estudios demuestran que el riesgo de mortalidad por COVID-19 en los no vacunados es 25 veces mayor que en los vacunados

A Nationwide Survey of mRNA COVID-19 Vaccinee's Experiences on Adverse Events and Its Associated Factors.

BACKGROUND: Although coronavirus disease 2019 (COVID-19) vaccines have been distributed worldwide under emergency use authorization, the real-world safety profiles of mRNA vaccines still need to be clearly defined. We aimed to identify the overall incidence and factors associated with adverse events (AEs) following mRNA COVID-19 vaccination. METHODS: We conducted web-based survey from December 2 to 10 in 2021 with a 2,849 nationwide sampled panel. Study participants were individuals who had elapsed at least two-weeks after completing two dosing schedules of COVID-19 vaccination aged between 18-49 years. We weighted the participants to represent the Korean population. The outcome was the overall incidence of AEs following mRNA COVID-19 vaccination and associated factors. We estimated the weighted odds ratios (ORs) using multivariable logistic regression models to identify the factors associated with AEs. RESULTS: Of the 2,849 participants (median [interquartile range] age, 35 [27-42] years; 51.6% male), 90.8% (n = 2,582) for the first dose and 88.7% (n = 2,849) for the second dose reported AEs, and 3.3% and 4.3% reported severe AEs, respectively. Occurrence of AEs was more prevalent in mRNA-1273 (OR, 2.06; 95% confidence interval [CI], 1.59-2.67 vs. BNT162b2), female sex (1.88; 1.52-2.32), and those with dermatologic diseases (2.51; 1.32-4.77). History of serious allergic reactions (1.96; 1.06-3.64) and anticoagulant medication use (4.72; 1.92-11.6) were associated with severe AEs. CONCLUSION: Approximately 90% of participants reported AEs following mRNA COVID-19 vaccination. Substantial factors, including vaccine type (mRNA-1273), female sex, and dermatologic diseases were associated with AEs. Our findings could aid policymakers in establishing vaccination strategies tailored to those potentially susceptible to AEs.

Does the SARS-CoV-2 mRNA vaccine damage the ovarian reserve?

To search whether or not the severe acute respiratory syndrome corona virus-2 (SARS-CoV-2) messenger ribonucleic acid (mRNA) vaccine affects the fertility of women at the 6th months by using AMH, which is an ovarian reserve test. Our study, designed as a prospective case-control study, included 104 women who presented to the GOP EAH obstetrics and gynecology outpatient clinic in January and February 2022. The study group included 74 women who presented to the outpatient clinic and planned to be vaccinated and 30 women who refused to be vaccinated as the control group. Anti-COVID-19 antibody levels in all participants were checked before participation in the study, and participants who were positive were excluded from the study. Blood was taken from the participants in both control and study groups to evaluate their AMH levels before the 2 doses of vaccination. After 2 doses of the vaccine, they were called for follow-up, and serological tests were performed to check whether they were positive for anti-COVID-19 antibodies. Participants in both groups were referred for follow-up after 6 months, samples were taken again for AMH, and the data were recorded. The mean age of the study group was 27.6 ±â€…5.3 years, and the mean age of the control group was 28.65 ±â€…5.25 years (P = .298). There was no statistically significant difference between the vaccinated and nonvaccinated groups in terms of AMH levels measured at the 6th month (P = .970). When the vaccinated group was compared in terms of AMH values at the first visit before vaccination and at the 6th month after vaccination, no statistically significant difference was found between them (p:0.127) mRNA vaccination to protect against SARS-CoV-2 does not adversely affect ovarian reserve, which is an indirect indicator of fertility. mRNA vaccines continue to be the most important method of protection against epidemics. Carefully and accurately informing women who are hesitant to get vaccinated is of great importance for the success of the fight against the epidemic.

The discovery and development of mRNA vaccines for the prevention of SARS-CoV-2 infection.

INTRODUCTION: COVID-19 pandemic is one of the most serious public health events of this century. There have been more than 670 million confirmed cases and more than 6 million deaths worldwide. From the emergence of the Alpha variant to the later rampant Omicron variant, the high transmissibility and pathogenicity of SARS-CoV-2 accelerate the research and development of effective vaccines. Against this background, mRNA vaccines stepped onto the historical stage and became an important tool for COVID-19 prevention. AREAS COVERED: This article introduces the characteristics of different mRNA vaccines in the prevention of COVID-19, including antigen selection, therapeutic mRNA design and modification, and different delivery systems of mRNA molecules. It also summarizes and discusses the mechanisms, safety, effectiveness, side effects, and limitations of current COVID-19 mRNA vaccines. EXPERT OPINION: Therapeutic mRNA molecules have plenty of advantages, including flexible design, rapid production, sufficient immune activation, safety without the risk of genome insertion in the host cells, and no viral vectors or particles involved, making them an important tool to fight diseases in the future. However, the application of COVID-19 mRNA vaccines also faces many challenges, such as storage and transportation, mass production, and nonspecific immunity.

Bivalent mRNA COVID-19 Vaccine-Related Pericarditis on 18 F-FDG PET/CT.

ABSTRACT: A 13-year-old boy was suspected with pericarditis after a second booster dose of bivalent mRNA COVID-19 vaccine. After specific preparation for cardiac inflammation with carbohydrate-free, high-fat diet, the 18 F-FDG PET/CT successfully demonstrated simultaneous presentation of vaccination-related axillary lymphadenopathy and pericarditis without the interference of physiological myocardial uptake.

Low energy nebulization preserves integrity of SARS-CoV-2 mRNA vaccines for respiratory delivery.

Nebulization of mRNA therapeutics can be used to directly target the respiratory tract. A promising prospect is that mucosal administration of lipid nanoparticle (LNP)-based mRNA vaccines may lead to a more efficient protection against respiratory viruses. However, the nebulization process can rupture the LNP vehicles and degrade the mRNA molecules inside. Here we present a novel nebulization method able to preserve substantially the integrity of vaccines, as tested with two SARS-CoV-2 mRNA vaccines. We compare the new method with well-known nebulization methods used for medical respiratory applications. We find that a lower energy level in generating LNP droplets using the new nebulization method helps safeguard the integrity of the LNP and vaccine. By comparing nebulization techniques with different energy dissipation levels we find that LNPs and mRNAs can be kept largely intact if the energy dissipation remains below a threshold value, for LNP integrity 5-10 J/g and for mRNA integrity 10-20 J/g for both vaccines.

[A case of severe inflammatory bowel disease triggered by vaccination with SARS-CoV-2 mRNA].

A 64-year-old woman received a third dose of SARS-CoV-2 mRNA vaccine. On the next day, she developed fever, diarrhea, and abdominal pain and had bloody stools. Total colonoscopy revealed deep ulceration on the whole colon. She was treated with corticosteroid and infliximab and her symptoms improved. She was diagnosed with severe enteritis resembling ulcerative colitis triggered by SARS-CoV-2 mRNA vaccination.

Potentiating the Cross-Reactive IFN-γ T Cell and Polyfunctional T Cell Responses by Heterologous GX-19N DNA Booster in Mice Primed with Either a COVID-19 mRNA Vaccine or Inactivated Vaccine.

Waning vaccine-induced immunity, coupled with the emergence of SARS-CoV-2 variants, has inspired the widespread implementation of COVID-19 booster vaccinations. Here, we evaluated the potential of the GX-19N DNA vaccine as a heterologous booster to enhance the protective immune response to SARS-CoV-2 in mice primed with either an inactivated virus particle (VP) or an mRNA vaccine. We found that in the VP-primed condition, GX-19N enhanced the response of both vaccine-specific antibodies and cross-reactive T Cells to the SARS-CoV-2 variant of concern (VOC), compared to the homologous VP vaccine prime-boost. Under the mRNA-primed condition, GX-19N induced higher vaccine-induced T Cell responses but lower antibody responses than the homologous mRNA vaccine prime-boost. Furthermore, the heterologous GX-19N boost induced higher S-specific polyfunctional CD4+ and CD8+ T cell responses than the homologous VP or mRNA prime-boost vaccinations. Our results provide new insights into booster vaccination strategies for the management of novel COVID-19 variants.

Oligonucleotide mapping via mass spectrometry to enable comprehensive primary structure characterization of an mRNA vaccine against SARS-CoV-2.

Oligonucleotide mapping via liquid chromatography with UV detection coupled to tandem mass spectrometry (LC-UV-MS/MS) was recently developed to support development of Comirnaty, the world's first commercial mRNA vaccine which immunizes against the SARS-CoV-2 virus. Analogous to peptide mapping of therapeutic protein modalities, oligonucleotide mapping described here provides direct primary structure characterization of mRNA, through enzymatic digestion, accurate mass determinations, and optimized collisionally-induced fragmentation. Sample preparation for oligonucleotide mapping is a rapid, one-pot, one-enzyme digestion. The digest is analyzed via LC-MS/MS with an extended gradient and resulting data analysis employs semi-automated software. In a single method, oligonucleotide mapping readouts include a highly reproducible and completely annotated UV chromatogram with 100% maximum sequence coverage, and a microheterogeneity assessment of 5' terminus capping and 3' terminus poly(A)-tail length. Oligonucleotide mapping was pivotal to ensure the quality, safety, and efficacy of mRNA vaccines by providing: confirmation of construct identity and primary structure and assessment of product comparability following manufacturing process changes. More broadly, this technique may be used to directly interrogate the primary structure of RNA molecules in general.

Genes Involved in miRNA Biogenesis Are Not Downregulated in SARS-CoV-2 Infection.

miRNAs, small non-coding RNAs that regulate gene expression, are involved in various pathological processes, including viral infections. Virus infections may interfere with the miRNA pathway through the inhibition of genes involved in miRNA biogenesis. A reduction in the number and the levels of miRNAs expressed in nasopharyngeal swabs of patients with severe COVID-19 was lately observed by us, pointing towards the potential of miRNAs as possible diagnostic or prognostic biomarkers for predicting outcomes among patients with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. The objective of the present study was to investigate whether SARS-CoV-2 infection influences the expression levels of messenger RNAs (mRNAs) of key genes involved in miRNA biogenesis. mRNA levels of AGO2, DICER1, DGCR8, DROSHA, and Exportin-5 (XPO5) were measured by quantitative reverse-transcription polymerase chain reaction (RT-qPCR) in nasopharyngeal swab specimens from patients with COVID-19 and controls, as well as in cells infected with SARS-CoV-2 in vitro. Our data showed that the mRNA expression levels of AGO2, DICER1, DGCR8, DROSHA, and XPO5 were not significantly different in patients with severe COVID-19 when compared to patients with non-severe COVID-19 and controls. Similarly, the mRNA expression of these genes was not affected by SARS-CoV-2 infection in NHBE and Calu-3 cells. However, in Vero E6 cells, AGO2, DICER1, DGCR8, and XPO5 mRNA levels were slightly upregulated 24 h after infection with SARS-CoV-2. In conclusion, we did not find evidence for downregulation of mRNA levels of miRNA biogenesis genes during SARS-CoV-2 infection, neither ex vivo nor in vitro.

Virus-Like Particles Are Efficient Tools for Boosting mRNA-Induced Antibodies.

mRNA based vaccines against COVID-19 have proven most successful at keeping SARS-CoV-2 pandemic at bay in many countries. Recently, there is an increased interest in heterologous prime-boost vaccination strategies for COVID-19 to maintain antibody responses for the control of continuously emerging SARS-CoV-2 variants of concern (VoCs) and to overcome other obstacles such as supply shortage, costs and reduced safety issues or inadequatly induced immune-responses. In this study, we investigated the antibody responses induced by heterologous prime-boost with vaccines based on mRNA and virus-like particles (VLPs). The VLP-based mCuMVTT-RBM vaccine candidate and the approved mRNA-1273 vaccine were used for this purpose. We find that homologous prime boost regimens with either mRNA or VLP induced high levels of high avidity antibodies. Optimal antibody responses were, however, induced by heterologous regimens both for priming with mRNA and boosting with VLP and vice versa, priming with VLP and boosting with mRNA. Thus, heterologous prime boost strategies may be able to optimize efficacy and economics of novel vaccine strategies.

Dynamic Evolution of Humoral and T-Cell Specific Immune Response to COVID-19 mRNA Vaccine in Patients with Multiple Sclerosis Followed until the Booster Dose.

This study characterizes antibody and T-cell immune responses over time until the booster dose of COronaVIrus Disease 2019 (COVID-19) vaccines in patients with multiple sclerosis (PwMS) undergoing different disease-modifying treatments (DMTs). We prospectively enrolled 134 PwMS and 99 health care workers (HCWs) having completed the two-dose schedule of a COVID-19 mRNA vaccine within the last 2-4 weeks (T0) and followed them 24 weeks after the first dose (T1) and 4-6 weeks after the booster (T2). PwMS presented a significant reduction in the seroconversion rate and anti-receptor-binding domain (RBD)-Immunoglobulin (IgG) titers from T0 to T1 (p < 0.0001) and a significant increase from T1 to T2 (p < 0.0001). The booster dose in PwMS showed a good improvement in the serologic response, even greater than HCWs, as it promoted a significant five-fold increase of anti-RBD-IgG titers compared with T0 (p < 0.0001). Similarly, the T-cell response showed a significant 1.5- and 3.8-fold increase in PwMS at T2 compared with T0 (p = 0.013) and T1 (p < 0.0001), respectively, without significant modulation in the number of responders. Regardless of the time elapsed since vaccination, most ocrelizumab- (77.3%) and fingolimod-treated patients (93.3%) showed only a T-cell-specific or humoral-specific response, respectively. The booster dose reinforces humoral- and cell-mediated-specific immune responses and highlights specific DMT-induced immune frailties, suggesting the need for specifically tailored strategies for immune-compromised patients to provide primary prophylaxis, early SARS-CoV-2 detection and the timely management of COVID-19 antiviral treatments.

Acute myopericarditis and left shoulder capsulitis following second dose of mRNA SARS-CoV-2 Moderna vaccination.

Vaccination against mRNA SARS-CoV-2 has been administered on a very large scale and various side effects have been described. The increased risk of myopericarditis is known, and only a few cases of shoulder capsulitis have been reported after vaccination. These two pathologies have never been reported in the same patient after vaccination. Our article presents the history of a man in his 40s who presented with myopericarditis a few days after vaccination against SARS-CoV-2 with mRNA(Messenger RNA) Moderna® vaccine and who at the same time developed shoulder capsulitis. His cardiovascular symptoms resolved rapidly, and his shoulder symptoms improved/resolved within 1 year. This case should make physicians aware of the possibility of several concomitant side effects following vaccination against SARS-CoV-2.

GRT-R910: a self-amplifying mRNA SARS-CoV-2 vaccine boosts immunity for ≥6 months in previously-vaccinated older adults.

SARS-CoV-2 has resulted in high levels of morbidity and mortality world-wide, and severe complications can occur in older populations. Humoral immunity induced by authorized vaccines wanes within 6 months, and frequent boosts may only offer transient protection. GRT-R910 is an investigational self-amplifying mRNA (samRNA)-based SARS-CoV-2 vaccine delivering full-length Spike and selected conserved non-Spike T cell epitopes. This study reports interim analyses for a phase I open-label dose-escalation trial evaluating GRT-R910 in previously vaccinated healthy older adults (NCT05148962). Primary endpoints of safety and tolerability were assessed. Most solicited local and systemic adverse events (AEs) following GRT-R910 dosing were mild to moderate and transient, and no treatment-related serious AEs were observed. The secondary endpoint of immunogenicity was assessed via IgG binding assays, neutralization assays, interferon-gamma ELISpot, and intracellular cytokine staining. Neutralizing antibody titers against ancestral Spike and variants of concern were boosted or induced by GRT-R910 and, contrasting to authorized vaccines, persisted through at least 6 months after the booster dose. GRT-R910 increased and/or broadened functional Spike-specific T cell responses and primed functional T cell responses to conserved non-Spike epitopes. This study is limited due to small sample size, and additional data from ongoing studies will be required to corroborate these interim findings.

Evaluation of menstrual symptoms after Coronavirus disease 2019 vaccination in women with endometriosis.

BACKGROUND: Vaccination can have an impact on menstruation, and this impact may be more notable in women with inflammatory gynecological pathologies such as endometriosis. OBJECTIVES: We aimed to investigate the impact of mRNA-based SARS-CoV-2 vaccines on menstrual cycle-related symptoms in women with endometriosis and assess the effect of hormonal therapy on potential SARS-CoV-2 vaccination-induced menstrual changes. DESIGN: A total of 848 women who received at least two doses of mRNA-based COVID-19 vaccines were prospectively recruited: 407 with endometriosis (endometriosis group) and 441 healthy controls (non-endometriosis group). METHODS: Data regarding demographics, clinical characteristics, hormonal treatment, and menstrual-associated symptoms in the first and second cycle after vaccination were collected through an online survey. RESULTS: A similar percentage of patients in both the endometriosis and the non-endometriosis group self-reported menstrual-associated changes the first (52.6% versus 48.8%, respectively) and second cycle after vaccination (29.0% versus 28.1%, respectively). Although the total symptoms recorded were not different between the two groups, several specific symptoms were statistically more frequent in the endometriosis group. These were pain disorders and fatigue in the first cycle after vaccination and pain disorders, menstrual headache and fatigue in the second cycle after vaccination. Bleeding frequency/regularity disorders were found to be more frequent in the non-endometriosis group in the first cycle after vaccination. Patients under hormonal treatment reported fewer changes in menstrual symptoms in the first and second cycle after vaccination compared with those not receiving this treatment. Similarly, patients in the endometriosis group receiving hormonal treatment reported fewer changes in menstrual-associated symptoms compared with those not following any hormonal treatment in the first and second menstrual cycle after the last vaccination. CONCLUSION: Women with endometriosis immunized with mRNA-based SARS-CoV-2 vaccines did not perceive greater worsening or new menstrual-associated symptoms after complete COVID-19 vaccination compared with healthy controls. Hormonal treatment may have a protective effect against worsened or new menstrual symptoms induced by COVID-19 vaccination.

SARS-CoV-2 bivalent mRNA vaccine with broad protection against variants of concern.

Introduction: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant has rapidly spread around the globe. With a substantial number of mutations in its Spike protein, the SARS-CoV-2 Omicron variant is prone to immune evasion and led to the reduced efficacy of approved vaccines. Thus, emerging variants have brought new challenges to the prevention of COVID-19 and updated vaccines are urgently needed to provide better protection against the Omicron variant or other highly mutated variants. Materials and methods: Here, we developed a novel bivalent mRNA vaccine, RBMRNA-405, comprising a 1:1 mix of mRNAs encoding both Delta-derived and Omicron-derived Spike proteins. We evaluated the immunogenicity of RBMRNA-405 in BALB/c mice and compared the antibody response and prophylactic efficacy induced by monovalent Delta or Omicron-specific vaccine with the bivalent RBMRNA-405 vaccine in the SARSCoV-2 variant challenge. Results: Results showed that the RBMRNA-405 vaccine could generate broader neutralizing antibody responses against both Wuhan-Hu-1 and other SARS-CoV-2 variants, including Delta, Omicron, Alpha, Beta, and Gamma. RBMRNA-405 efficiently blocked infectious viral replication and lung injury in both Omicron- and Delta-challenged K18-ACE2 mice. Conclusion: Our data suggest that RBMRNA-405 is a promising bivalent SARS-CoV-2 vaccine with broad-spectrum efficacy for further clinical development.

Current hotspot and study trend of innate immunity in COVID-19: a bibliometric analysis from 2020 to 2022.

Background: Since the coronavirus disease 2019 (COVID-19) has spread throughout the world, many studies on innate immunity in COVID-19 have been published, and great progress has been achieved, while bibliometric analysis on hotspots and research trends in this field remains lacking. Methods: On 17 November 2022, articles and reviews on innate immunity in COVID-19 were recruited from the Web of Science Core Collection (WoSCC) database after papers irrelevant to COVID-19 were further excluded. The number of annual publications and the average citations per paper were analyzed by Microsoft Excel. Bibliometric analysis and visualization of the most prolific contributors and hotspots in the field were performed by VOSviewer and CiteSpace software. Results: There were 1,280 publications that met the search strategy on innate immunity in COVID-19 and were published from 1 January 2020 to 31 October 2022. Nine hundred thirteen articles and reviews were included in the final analysis. The USA had the highest number of publications (Np) at 276 and number of citations without self-citations (Nc) at 7,085, as well as an H-index of 42, which contributed 30.23% of the total publications, followed by China (Np: 135, Nc: 4,798, and H-index: 23) with 14.79% contribution. Regarding Np for authors, Netea, Mihai G. (Np: 7) from the Netherlands was the most productive author, followed by Joosten, Leo A. B. (Np: 6) and Lu, Kuo-Cheng (Np: 6). The Udice French Research Universities had the most publications (Np: 31, Nc: 2,071, H-index: 13), with an average citation number (ACN) at 67. The journal Frontiers in Immunology possessed the most publications (Np: 89, Nc: 1,097, ACN: 12.52). "Evasion" (strength 1.76, 2021-2022), "neutralizing antibody" (strength 1.76, 2021-2022), "messenger RNA" (strength 1.76, 2021-2022), "mitochondrial DNA" (strength 1.51, 2021-2022), "respiratory infection" (strength 1.51, 2021-2022), and "toll-like receptors" (strength 1.51, 2021-2022) were the emerging keywords in this field. Conclusion: The study on innate immunity in COVID-19 is a hot topic. The USA was the most productive and influential country in this field, followed by China. The journal with the most publications was Frontiers in Immunology. "Messenger RNA," "mitochondrial DNA," and "toll-like receptors" are the current hotspots and potential targets in future research.

Comparative mRNA booster effectiveness against death or hospitalization with COVID-19 pneumonia across at-risk US Veteran populations.

Studies of comparative mRNA booster effectiveness among high-risk populations can inform mRNA booster-specific guidelines. The study emulated a target trial of COVID-19 vaccinated U.S. Veterans who received three doses of either mRNA-1273 or BNT162b2 vaccines. Participants were followed for up to 32 weeks between July 1, 2021 to May 30, 2022. Non-overlapping populations were average and high risk; high-risk sub-groups were age ≥65 years, high-risk co-morbid conditions, and immunocompromising conditions. Of 1,703,189 participants, 10.9 per 10,000 persons died or were hospitalized with COVID-19 pneumonia over 32 weeks (95% CI: 10.2, 11.8). Although relative risks of death or hospitalization with COVID-19 pneumonia were similar across at-risk groups, absolute risk varied when comparing three doses of BNT162b2 with mRNA-1273 (BNT162b2 minus mRNA-1273) between average-risk and high-risk populations, confirmed by the presence of additive interaction. The risk difference of death or hospitalization with COVID-19 pneumonia for high-risk populations was 2.2 (0.9, 3.6). Effects were not modified by predominant viral variant. In this work, the risk of death or hospitalization with COVID-19 pneumonia over 32 weeks was lower among high-risk populations who received three doses of mRNA-1273 vaccine instead of BNT162b2 vaccine; no difference was found among the average-risk population and age >65 sub-group.

Effectiveness of COVID-19 Pfizer-BioNTech (BNT162b2) mRNA vaccination in adolescents aged 12-17 years: A systematic review and meta-analysis.

The rapid emergence of COVID-19 variants of concern (VOCs) has hindered vaccine uptake. To inform policy, we investigated the effectiveness of the BNT162b2 vaccination among adolescents against symptomatic and severe COVID-19 diseases using mostly real-world data (15 studies). We searched international databases until May 2022 and used Cochrane's risk of bias tools for critical appraisal. Random effects models were used to examine overall vaccine effectiveness (VE) across studies (general inverse-variance) and the effect of circulating VOCs on VE (log relative ratio and VE). Meta-regression assessed the effect of age and time on VE (restricted-maximum likelihood). BNT162b2 VE against PCR-confirmed SARS-CoV-2 was 82.7% (95%CI: 78.37-87.31%). VE was higher for severe (88%) than non-severe (35%) outcomes and declining over time improved following booster dose in omicron era [73%(95%CI:65-81%)]. Fully vaccinated adolescents are protected from COVID-19 circulating VOCs by BNT162b2 especially for the need of critical care or life support.