Development of myocarditis and pericarditis after COVID-19 vaccination in adult population: A systematic review

Post-COVID-19 vaccination myocarditis: a prospective cohort study pre and post vaccination using cardiovascular magnetic resonance

BACKGROUND

Concerns about COVID-19 vaccination induced myocarditis or subclinical myocarditis persists in some populations. Cardiac magnetic resonance imaging (CMR) has been used to detect signs of COVID-19 vaccination induced myocarditis. This study aims to: (i) characterise myocardial tissue, function, size before and after COVID-19 vaccination, (ii) determine if there is imaging evidence of subclinical myocardial inflammation or injury after vaccination using CMR.

METHODS

Subjects aged ≥ 12yrs old without prior COVID-19 or COVID-19 vaccination underwent two CMR examinations: first, ≤ 14 days before the first COVID-19 vaccination and a second time ≤ 14 days after the second COVID-19 vaccination. Biventricular indices, ejection fraction (EF), global longitudinal strain (GLS), late gadolinium enhancement (LGE), left ventricular (LV) myocardial native T1, T2, extracellular volume (ECV) quantification, lactate dehydrogenase (LDH), white cell count (WCC), C-reactive protein (CRP), NT-proBNP, troponin-T, electrocardiogram (ECG), and 6-min walk test were assessed in a blinded fashion.

RESULTS

67 subjects were included. First and second CMR examinations were performed a median of 4 days before the first vaccination (interquartile range 1-8 days) and 5 days (interquartile range 3-6 days) after the second vaccination respectively. No significant change in global native T1, T2, ECV, LV EF, right ventricular EF, LV GLS, LGE, ECG, LDH, troponin-T and 6-min walk test was demonstrated after COVID-19 vaccination. There was a significant WCC decrease (6.51 ± 1.49 vs 5.98 ± 1.65, p = 0.003) and CRP increase (0.40 ± 0.22 vs 0.50 ± 0.29, p = 0.004).

CONCLUSION

This study found no imaging, biochemical or ECG evidence of myocardial injury or inflammation post COVID-19 vaccination, thus providing some reassurance that COVID-19 vaccinations do not typically cause subclinical myocarditis.

Myopericarditis as a Delayed Complication of COVID-19 Infection: A Case Report

Pericarditis is the inflammation of the pericardial layers. Myopericarditis is diagnosed when this inflammation involves the myocardium, which is marked by elevated serum cardiac enzymes. With these two pathologies sharing overlaps in etiology, we present a case of a young patient with a recent history of COVID-19 infection who presented with pleuritic and positional chest pain with troponin I elevation and serial ECG changes attributed to myopericarditis as a post-viral sequela of severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) infection. This case demonstrates the importance of identifying and managing the potential cardiac complications in coronavirus disease 2019 (COVID-19) patients, regardless of age or symptom onset.

Covid- 19 Vaccine-induced Myocarditis

Myocarditis and pericarditis are rare adverse reactions, more commonly seen in young males after receiving the second dose of an mRNA vaccine. However, the benefits of vaccination heavily outweigh the risk of these side effects. In addition, vaccination boosters are effective against the newest, more infective variants. Therefore we expect more vaccines to be administered in the following years. The objective of this study is to review the current understanding of the mechanism, diagnosis, and treatment of myocarditis and pericarditis. Proposed mechanisms include molecular mimicry against the S protein and hypersensitivity reactions with mRNA vaccines and platelet aggregation and thrombus formation in cardiac blood vessels with adenoviral vaccines. Diagnosis of myocarditis is based on clinical findings, cardiac enzymes, ECG, MRI, and echocardiographic findings. Management includes NSAIDs and cardiovascular support in selected cases with ventricular dysfunction. Most patients have a mild presentation with preservation of cardiac function and recover entirely within seven days; the average hospital stay is three days. Long-term complications are infrequent.

Single cell characteristics of patients with vaccine-related adverse reactions following inactivated COVID-19 vaccination

A good safety and immunogenicity profile was reported in Phase I and II clinical trials of inactivated SARS-CoV-2 vaccines. Here, we report two cases associated with vaccine-associated adverse events, including one patient with fever and another with anaphylactic shock resulting from inactivated SARS-CoV-2 vaccination. Cell sub-types and the importance of genetic characteristics were assessed using single-cell mRNA sequencing and machine learning. Overall, the patient with fever showed a significant increase in the numbers of cytotoxic CD8 T cells and MKI67high CD8 T cells. A potential concurrent infection with the Epstein-Barr virus enhanced interferon type I responses to vaccination against the virus. STAT1, E2F1, YBX1, and E2F7 played a key role in the transcription regulation of MKI67high CD8 T cells. In contrast, the patient with allergic shock displayed predominant increases in the numbers of S100A9high monocytes, activated CD4 T cells, and PPBPhigh megakaryocytes. The decision tree showed that LYZ and S100A8 in S100A9high monocytes contributed to the degranulation of neutrophils and activation of neutrophils involved in allergic shock. PPBP and PF4 were major contributors to platelet degranulation. These findings highlight the diversity of adverse reactions following inactivated SARS-CoV-2 vaccination and show the emerging role of cellular subtypes and central genes in vaccine-associated adverse reactions.

Risk of myocarditis and pericarditis in mRNA COVID-19-vaccinated and unvaccinated populations: a systematic review and meta-analysis

OBJECTIVE

To summarise the available evidence on the risk of myocarditis and/or pericarditis following mRNA COVID-19 vaccination, compared with the risk among unvaccinated individuals in the absence of COVID-19 infection.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Electronic databases (Medline, Embase, Web of Science and WHO Global Literature on Coronavirus Disease), preprint repositories (medRxiv and bioRxiv), reference lists and grey literature were searched from 1 December 2020 until 31 October 2022.

STUDY SELECTION

Epidemiological studies of individuals of any age who received at least one dose of an mRNA COVID-19 vaccine, reported a risk of myo/pericarditis and compared the risk of myo/pericarditis to individuals who did not receive any dose of an mRNA COVID-19 vaccine.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently conducted screening and data extraction. The rate of myo/pericarditis among vaccinated and unvaccinated groups was recorded, and the rate ratios were calculated. Additionally, the total number of individuals, case ascertainment criteria, percentage of males and history of SARS-CoV-2 infection were extracted for each study. Meta-analysis was done using a random-effects model.

RESULTS

Seven studies met the inclusion criteria, of which six were included in the quantitative synthesis. Our meta-analysis indicates that within 30-day follow-up period, vaccinated individuals were twice as likely to develop myo/pericarditis in the absence of SARS-CoV-2 infection compared to unvaccinated individuals, with a rate ratio of 2.05 (95% CI 1.49-2.82).

CONCLUSION

Although the absolute number of observed myo/pericarditis cases remains quite low, a higher risk was detected in those who received mRNA COVID-19 vaccinations compared with unvaccinated individuals in the absence of SARS-CoV-2 infection. Given the effectiveness of mRNA COVID-19 vaccines in preventing severe illnesses, hospitalisations and deaths, future research should focus on accurately determining the rates of myo/pericarditis linked to mRNA COVID-19 vaccines, understanding the biological mechanisms behind these rare cardiac events and identifying those most at risk.

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.

Short term outcome of myocarditis and pericarditis following COVID-19 vaccines: a cardiac magnetic resonance imaging study

To evaluate clinical and cardiac magnetic resonance (CMR) short-term follow-up (FU) in patients with vaccine-associated myocarditis, pericarditis or myo-pericarditis (VAMP) following COVID-19 vaccination. We retrospectively analyzed 44 patients (2 women, mean age: 31.7 ± 15.1 years) with clinical and CMR manifestations of VAMP, recruited from 13 large tertiary national centers. Inclusion criteria were troponin raise, interval between the last vaccination dose and onset of symptoms < 25 days and symptoms-to-CMR < 20 days. 29/44 patients underwent a short-term FU-CMR with a median time of 3.3 months. Ventricular volumes and CMR findings of cardiac injury were collected in all exams. Mean interval between the last vaccination dose and the onset of symptoms was 6.2 ± 5.6 days. 30/44 patients received a vaccination with Comirnaty, 12/44 with Spikevax, 1/44 with Vaxzevria and 1/44 with Janssen (18 after the first dose of vaccine, 20 after the second and 6 after the "booster" dose). Chest pain was the most frequent symptom (41/44), followed by fever (29/44), myalgia (17/44), dyspnea (13/44) and palpitations (11/44). At baseline, left ventricular ejection fraction (LV-EF) was reduced in 7 patients; wall motion abnormalities have been detected in 10. Myocardial edema was found in 35 (79.5%) and LGE in 40 (90.9%) patients. Clinical FU revealed symptoms persistence in 8/44 patients. At FU-CMR, LV-EF was reduced only in 2 patients, myocardial edema was present in 8/29 patients and LGE in 26/29. VAMPs appear to have a mild clinical presentation, with self-limiting course and resolution of CMR signs of active inflammation at short-term follow-up in most of the cases.

Current evidence of COVID-19 vaccination-related cardiovascular events

Currently, the world is recovering from the shock of the coronavirus disease 2019 (COVID-19) pandemic; however, this situation is still fragile. Health authorities recommend administering COVID-19 vaccines as the safest and most reliable tool for eliminating COVID-19. Subsequent to the extensive administration of the COVID-19 vaccines, a series of cardiovascular adverse effects have been reported. This comprehensive review aimed to provide an update on the etiology, pathophysiology, clinical features, and management of the cardiovascular adverse events associated with COVID-19 vaccines, including myocarditis, pericarditis, thrombosis with thrombocytopenia syndrome, myocardial infarction, cardiac arrhythmias, hypertension, and stress-induced cardiomyopathy. The benefits of COVID-19 vaccination far outweigh the reported adverse events. It would be clinically important to provide diagnostic scoring systems to differentiate COVID-19-related cardiovascular adverse events from other causes and develop therapeutic approaches for their management. Further evaluation of cardiovascular adverse events of the COVID-19 vaccines is crucial for implementing vaccination programs and developing safer and more reliable vaccines.

Development of myocarditis and pericarditis after COVID-19 vaccination in children and adolescents: A systematic review

Myocarditis and pericarditis have been reported after COVID-19 vaccine administration in children and adolescents, raising the concern about their possible association with these vaccines. The objective was to explore the incidence, clinical presentation, and association of myocarditis and pericarditis with COVID-19 vaccines in children and adolescents. We conducted a systematic literature search on three databases, that is, Cochrane, MEDLINE/PubMed, and EMBASE from inception till March 2022. A total of three case reports, four case series, and six observational studies were included in the review. For case reports and case series, the mean age of the patients was 17.4 years, with 96.9% being male. Chest pain (n = 31, 93.9%), fever (n = 18, 54.5%), myalgias (n = 15, 45.4%) and headache (n = 9, 27.2%) were the most common presentations. Out of 33 patients, 32 (96.9%) of patients received Pfizer-BioNTech whereas only one (3.03%) received Moderna (mRNA 1273). Clinical investigations revealed ST elevation (n = 32, 97%), and elevated CRP (n = 9, 27.2%) and cardiac troponin (n = 29, 87.8%). The pooled incidence of myocarditis and pericarditis from observational studies was (0.00063%) and (0.000074%) %, respectively. Myocarditis and pericarditis in children and adolescents after the COVID-19 vaccines were more prevalent among males and more commonly observed after the second dose of Pfizer. Though the overall incidence was low, however, the clinicians should consider myocarditis and pericarditis as probable diagnosis when encountering young patients, with a history of vaccine administration, presenting with suggestive findings.

A 1-year analysis of adverse events following COVID-19 vaccination in Lebanon: a retrospective study

BACKGROUND

Since the deployment of Coronavirus Disease 2019 (COVID-19) vaccines, skepticism about the safety, incidence, and severity of Adverse Events Following Immunization (AEFI) was a concern. The study has two main objectives. First, to analyze AEFIs following COVID-19 vaccines (Pfizer-BioNTech, AstraZeneca, Sputnik, and Sinopharm) during the vaccination campaign in Lebanon and correlate them with age and gender. Second, to correlate Pfizer-BioNTech and AstraZeneca vaccines' AEFI with the dose administered.

METHODS

A retrospective study was carried out between February 14th, 2021, and February 14th, 2022. AEFI case reports received to the Lebanese Pharmacovigilance (PV) Program were cleaned, validated, and analyzed using SPSS software.

RESULTS

A total of 6808 AEFI case reports were received to the Lebanese PV Program during the period of this study. Case reports were mostly received from females (60.7%) and from vaccine recipients aged 18-44 years. As for the vaccine type, AEFIs occurred more frequently with the AstraZeneca vaccine compared to the Pfizer-BioNTech vaccine. The latter had AEFIs mainly following dose 2, whereas AEFIs with the AstraZeneca vaccine were more frequently reported after dose 1, with general body pain being the most reported systemic AEFI with PZ (34.6%), while fatigue was the most reported AEFI with AZ vaccine (56.5%).

CONCLUSIONS

The AEFI reported with COVID-19 vaccines in Lebanon were aligned with those reported worldwide. The incidence of rare serious AEFIs should not discourage the public from getting vaccinated. Further studies are needed to evaluate their long-term potential risk.

A Systematic Review and Meta-analysis of the Association Between SARS-CoV-2 Vaccination and Myocarditis or Pericarditis

INTRODUCTION

There have been reports of potential negative cardiovascular effects from the COVID-19 vaccine, such as myocarditis or pericarditis. This study sought to ascertain the risk of myocarditis/pericarditis after COVID-19 vaccination by conducting an extensive meta-analysis of published cases.

METHODS

A systematic literature search was conducted in 7 online databases by March 31, 2022. Heterogeneity was tested by I² index. RR and 95% CI were pooled through either random-effect or fixed-effect models. Sensitivity analysis and publication bias were also conducted.

RESULTS

A total of 11 studies with 58,620,611 subjects were included. COVID-19 vaccination correlated with an increased risk of myocarditis or pericarditis (RR=2.04; 95% CI=1.33, 3.14). In addition, an increased risk of myocarditis or pericarditis in people who received the second dose of COVID-19 vaccine compared with that in those who received only the first dose of COVID-19 vaccine was also found (RR=4.06; 95% CI=2.08, 7.92). An increased incidence of pericarditis or myocarditis was noted predominantly in those who received BNT162b2 and mRNA-1273 vaccines (RR=2.19; 95% CI=1.46, 3.29 and RR=4.15; 95% CI=1.87, 9.22, respectively).

DISCUSSION

Study results indicate that a higher incidence of myocarditis or pericarditis was found after COVID-19 vaccination. In addition, the risk of developing myocarditis or pericarditis was greater after the second dose than after the first dose. Nevertheless, the risks of myocarditis and pericarditis in COVID-19 vaccine recipients are still significantly lower than the health risks observed in patients with COVID-19. Therefore, the benefits and harms must be carefully assessed to determine the best management option for patients who are in the high-risk group of myocarditis or pericarditis.

A prospective observational study to evaluate the safety of COVID-19 mRNA vaccines administered to Qatar Rehabilitation Institute patients

BACKGROUND

The safety of the COVID-19 mRNA vaccine in the outpatient setting has been extensively studied; however, there need to be more reports that specifically assess their safety in the inpatient population. It is hence imperative to explore the adverse drug reaction (ADR) profile in this population and monitor the progression of these ADRs in a hospital setting. This provides a unique opportunity to closely observe patients to ensure no side effects go undiagnosed. This study aims to explore and quantify the incidence and severity of ADRs in patients who have received the COVID-19 vaccine during their stay in the rehabilitation facility.

METHODS

This is a prospective observational study, which included adult patients admitted to the rehabilitation facility who were deemed eligible to receive the COVID-19 vaccine during their hospital stay. Data were collected by the investigators from June 2021 to May 2022 at 24 hours, 48 hours, and 7 days post-vaccination. A piloted data collection tool was utilized.

RESULTS

Thirty-five patients met the inclusion criteria. Pain at the injection site was the most commonly reported local ADR, while headache was the most frequent systemic ADR. The majority of the reported ADRs were mild to moderate in nature, with only one severe reaction detected. Although no statistical significance was noted among the variables, common patterns were identified, such as a higher occurrence of fever at 24 hours after the second dose as opposed to the first dose. Close monitoring of the included study subjects did not reveal any unanticipated ADRs or an increase in ADRs susceptibility and severity compared to the general population.

CONCLUSION

This study supports the initiation of vaccination campaigns in inpatient rehabilitation settings. This approach would offer the advantage of gaining full immunity and reducing the risk of contracting COVID-19 infection and complications once discharged.

The heart and SARS-CoV-2

SARS-Cov2 is currently causing a persistent Covid-19 pandemic, which poses a risk of causing long-term cardiovascular sequels in the population. The viral mechanism of cell infection through the angiotensin 2 converter enzyme receptor and the limited antiviral innate immune response are the suspected causes for a more frequent cardiovascular damage in SARS-Cov2 infection. Knowledge of: the appearance during acute infection of other cardiac conditions beyond the classical myocarditis and pericarditis), the long-term cardiac manifestations (persistent Covid-19), and the increased incidence of myocarditis and pericarditis after vaccination; it is of special interest in order to offer our patients best practices based on current scientific evidence.

Corazón y SARS-Cov2

El SARS-CoV-2 está causando actualmente una pandemia sostenida de COVID-19, con el riesgo de causar secuelas cardiacas a largo plazo en la población. El temor de que el SARS-CoV-2 cause un daño miocárdico mayor que otros virus convencionales se basa en su mecanismo de infección de células humanas a través del receptor de la enzima convertidora de la angiotensina 2 y las defensas antivirales innatas, hasta ahora reducidas contra un nuevo virus. El conocimiento de la aparición durante la infección aguda de otras afectaciones cardiacas, además de las clásicas miocarditis y pericarditis, las manifestaciones cardiacas observadas a largo plazo (COVID-19 persistente) y la incidencia incrementada de miocarditis y pericarditis tras la vacunación resulta de especial interés a fin de ofrecer a nuestros pacientes la mejor atención posible basada en la evidencia científica actual.

COVID-19 Vaccine-Induced Myocarditis: A Systemic Review and Literature Search

Myocarditis is one of the complications reported with COVID-19 vaccines, particularly both Pfizer-BioNTech and Moderna vaccines. Most of the published data about this association come from case reports and series. Integrating the geographical data, clinical manifestations, and outcomes is therefore important in patients with myocarditis to better understand the disease. A thorough literature search was conducted in Cochrane library, PubMed, ScienceDirect, and Google Scholar for published literature till 30 March 2022. We identified 26 patients eligible from 29 studies; the data were pooled from these qualifying case reports and case series. Around 94% of patients were male in this study, the median age for onset of myocarditis was 22 years and 85% developed symptoms after the second dose. The median time of admission for patients to hospitals post-vaccination was three days and chest pain was the most common presenting symptom in these patients. Most patients had elevated troponin on admission and about 90% of patients had cardiac magnetic resonance imaging (CMR) that showed late gadolinium enhancement. All patients admitted with myocarditis were discharged home after a median stay of four days. Results from this current analysis show that post-mRNA vaccination myocarditis is mainly seen in young males after the second dose of vaccination. The pathophysiology of vaccine-induced myocarditis is not entirely clear and late gadolinium enhancement is a common finding on CMR in these patients that may indicate myocardial fibrosis or necrosis. Prognosis remains good and all patients recovered from myocarditis, however further studies are advisable to assess long-term prognosis of myocarditis.

Global reports of myocarditis following COVID-19 vaccination: A systematic review and meta-analysis

BACKGROUND AND AIMS

Recent media reports of myocarditis after receiving COVID-19 vaccines, particularly the messenger RNA (mRNA) vaccines, are causing public concern. This review summarizes information from published case series and case reports, emphasizing patient and disease characteristics, investigation, and clinical outcomes, to provide a comprehensive picture of the condition.

METHODS

A systematic literature search of PubMed and Google scholar was conducted from inception to April 27, 2022. Individuals who develop myocarditis after receiving the COVID-19 vaccine, regardless of the type of vaccine and dose, were included in the study.

RESULTS

Sixty-two studies, including 218 cases, participated in the current systematic review. The median age was 29.2 years; 92.2% were male and 7.8% were female. 72.4% of patients received the Pfizer-BioNTech (BNT162b2) vaccine, 23.8% of patients received the Moderna COVID-19 Vaccine (mRNA-1273), and the rest of the 3.5% received other types of COVID-19 vaccine. Furthermore, most myocarditis cases (82.1%) occurred after the second vaccine dose, after a median time interval of 3.5 days. The most frequently reported symptoms were chest pain, myalgia/body aches and fever. Troponin levels were consistently elevated in 98.6% of patients. The admission ECG was abnormal in 88.5% of cases, and the left LVEF was lower than 50% in 21.5% of cases. Most patients (92.6%) resolved symptoms and recovered, and only three patients died.

CONCLUSION

These findings may help public health policy to consider myocarditis in the context of the benefits of COVID-19 vaccination.

COVID-19 Pandemic-Revealed Consistencies and Inconsistencies in Healthcare: A Medical and Organizational View

The circumstances of the Coronavirus disease caused by the SARS-CoV-2 virus (COVID-19) pandemic have had a significant impact on global and national developments, affecting the existence of society in all its expressions, as well as the lives of people themselves. In the context of the pandemic, increased attention has been focused on acute measures, but the ending of the pandemic is expected as a resolution of the related healthcare problems. However, there are several indicators that the COVID-19 pandemic might induce long-term consequences for individual and public health. Some of the consequences are inferred and predictable, but there are also areas of medicine that have been indirectly affected by the pandemic, and these consequences have not yet been sufficiently explored. This study is focused on drawing attention to some of the COVID-19 pandemic consistencies and the pandemic-revealed inconsistencies in healthcare. Content analysis and statistical analysis were applied to achieve the aim of the study. The main findings of the study address chronic disease burden (particularly, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)), healthcare governance and organizational issues, and the synergy between health policy perspectives and innovative solutions in practice. The study provides insight into the particular healthcare issues affected by the COVID-19 pandemic, such as the increase in mortality in some diagnoses besides COVID-19 and the possible emergence of a new type of resistance—vaccine-resistance—contemporaneously supporting the identification of the tendencies and currently unnoticed indirect consistencies and inconsistencies revealed by the pandemic.

Using industrial 4.0 technologies to combat the COVID-19 pandemic

The COVID 19 (Coronavirus) pandemic has led to a surge in the demand for healthcare devices, pre-cautions, or medicines along with advanced information technology. It has become a global mission to control the Coronavirus to prevent the death of innocent people. The fourth industrial revolution (I4.0) is a new approach to thinking that is proposed across a wide range of industries and services to achieve greater success and quality of life. Several initiatives associated with industry 4.0 are expected to make a difference in the fight against COVID-19. Implementing I4.0 components effectively could lead to a reduction in barriers between patients and healthcare workers and could result in improved communication between them. The present study aims to review the components of I4.0 and related tools used to combat the Coronavirus. This article highlights the benefits of each component of the I4.0, which is useful in controlling the spread of COVID-19. From the present study, it is stated that I4.0 technologies could provide an effective solution to deal with local as well as global medical crises in an innovative way.

Biological and Immune Responses to Current Anti-SARS-CoV-2 mRNA Vaccines beyond Anti-Spike Antibody Production

Several vaccine strategies are now available to fight the current SARS-CoV-2 pandemic. Those based on the administration of lipid-complexed messenger(m)RNA molecules represent the last frontiers in terms of technology innovation. mRNA molecules coding for the SARS-CoV-2 Spike protein are intramuscularly injected, thereby entering cells by virtue of their encapsulation into synthetic lipid nanovesicles. mRNA-targeted cells express the Spike protein on their plasma membrane in a way that it can be sensed by the immune system, which reacts generating anti-Spike antibodies. Although this class of vaccines appears as the most effective against SARS-CoV-2 infection and disease, their safety and efficiency are challenged by several factors included, but not limited to the following: emergence of viral variants, lack of adequate pharmacokinetics/pharmacodynamics studies, inability to protect oral mucosa from infection, and antibody waning. Emergence of viral variants can be a consequence of mass vaccination carried out in a pandemic time using suboptimal vaccines against an RNA virus. On the other hand, understanding the remainder flaws could be of some help in designing next generation anti-SARS-CoV-2 vaccines. In this commentary, issues regarding the fate of injected mRNA, the tissue distribution of the induced antiviral antibodies, and the generation of memory B cells are discussed. Careful evaluation of both experimental and clinical observations on these key aspects should be taken into account before planning booster administration, vaccination to non-at-risk population, and social restrictions.