Effectiveness of COVID-19 Vaccines in the General Population of an Italian Region before and during the Omicron Wave

Clinical-laboratory characteristics predictive of COVID-19 severity: a prospective hospital cohort, in Pernambuco, Northeast Brazil

OBJECTIVE

To describe the clinical-laboratory profile and analyze the factors associated with the severity of COVID-19.

METHODS

A prospective cohort study involving patients with COVID-19 admitted to a tertiary hospital in Recife, Brazil. All cases were confirmed by RT-PCR and classified according to severity criteria. A descriptive statistical analysis of the population's characteristics was conducted. Risk factors associated with the outcome of the case according to severity were analyzed by calculating the odds ratio (OR) using the general equation estimation (GEE) model.

RESULTS

Among the 75 cases included, 64% were female, and 62.7% were aged 65 years or older. The median length of stay was 9 days (6 - 14). Hypertension (65.3%) and Diabetes Mellitus (36%) were the most frequent comorbidities. Severe forms of COVID-19 constituted 41.3% of the sample. The factors associated with severity were a history of asthma (OR=4.58, 95%CI:1.13 - 18.7), report of anorexia (OR=1, 12, 95%CI:1.01-1.24), and laboratory changes that included elevated platelets (OR=1.00, 95% CI:1.00-1.01), elevated D'Dimer (OR=1, 26, 95% CI:1.04-1.52), elevated aspartate aminotransferase (OR=1.00, 95% CI:1.00-1.01), and gamma-glutamyl transferase (OR=1.22, IC95 %:0.98-1.51), hypernatremia (OR=1.31, 95%CI:1.12-1.52), and hyperkalemia (OR=1.21, 95% CI:1.04-1.41).

CONCLUSION

Multisystemic involvement with a tendency for thrombophilia, electrolyte disturbances, and hepatic aggression, reflected by laboratory changes, were factors associated with the severity of COVID-19.

Protection of the third-dose and fourth-dose mRNA vaccines against SARS-CoV-2 Omicron subvariant: a systematic review and meta-analysis

OBJECTIVES

The rapid spread of the SARS-CoV-2 Omicron variant has raised concerns regarding waning vaccine-induced immunity and durability. We evaluated protection of the third-dose and fourth-dose mRNA vaccines against SARS-CoV-2 Omicron subvariant and its sublineages.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Electronic databases and other resources (PubMed, Embase, CENTRAL, MEDLINE, CINAHL PLUS, APA PsycINFO, Web of Science, Scopus, ScienceDirect, MedRxiv and bioRxiv) were searched until December 2022.

STUDY ELIGIBILITY CRITERIA

We included studies that assessed the effectiveness of mRNA vaccine booster doses against SARS-CoV-2 infection and severe COVID-19 outcomes caused by the subvariant.

DATA EXTRACTION AND SYNTHESIS

Estimates of vaccine effectiveness (VE) at different time points after the third-dose and fourth-dose vaccination were extracted. Random-effects meta-analysis was used to compare VE of the third dose versus the primary series, no vaccination and the fourth dose at different time points. The certainty of the evidence was assessed by Grading of Recommendations, Assessments, Development and Evaluation approach.

RESULTS

This review included 50 studies. The third-dose VE, compared with the primary series, against SARS-CoV-2 infection was 48.86% (95% CI 44.90% to 52.82%, low certainty) at ≥14 days, and gradually decreased to 38.01% (95% CI 13.90% to 62.13%, very low certainty) at ≥90 days after the third-dose vaccination. The fourth-dose VE peaked at 14-30 days (56.70% (95% CI 50.36% to 63.04%), moderate certainty), then quickly declined at 61-90 days (22% (95% CI 6.40% to 37.60%), low certainty). Compared with no vaccination, the third-dose VE was 75.84% (95% CI 40.56% to 111.12%, low certainty) against BA.1 infection, and 70.41% (95% CI 49.94% to 90.88%, low certainty) against BA.2 infection at ≥7 days after the third-dose vaccination. The third-dose VE against hospitalisation remained stable over time and maintained 79.30% (95% CI 58.65% to 99.94%, moderate certainty) at 91-120 days. The fourth-dose VE up to 60 days was 67.54% (95% CI 59.76% to 75.33%, moderate certainty) for hospitalisation and 77.88% (95% CI 72.55% to 83.21%, moderate certainty) for death.

CONCLUSION

The boosters provided substantial protection against severe COVID-19 outcomes for at least 6 months, although the duration of protection remains uncertain, suggesting the need for a booster dose within 6 months of the third-dose or fourth-dose vaccination. However, the certainty of evidence in our VE estimates varied from very low to moderate, indicating significant heterogeneity among studies that should be considered when interpreting the findings for public health policies.

PROSPERO REGISTRATION NUMBER

CRD42023376698.

COVID-19 vaccination effectiveness in the population of Friuli Venezia Giulia, North-East Italy. Control of bias associated with divergent compliance to policies in a test-negative case-control study

BACKGROUND

Vaccine effectiveness (VE) studies consolidate knowledge of real-world effectiveness in different contexts. However, methodological issues may undermine their conclusions: to assess the VE against COVID-19 within the Italian population, a specific threat to validity is related to the consequences of divergent compliance to the Green Pass policy.

METHODS

To address this challenge we conducted a test negative case-control (TNCC) study and multiple sensitivity analysis among residents aged ≥ 12 in Friuli Venezia Giulia Region (FVG), North-east Italy, from February 1, 2021 to March 31, 2022. Information regarding 211,437 cases of COVID-19 infection and 845,748 matched controls was obtained from the regional computerized health database. The investigation considered: COVID-19 infection, hospitalization, and death. Multiple conditional logistic regressions adjusted for covariates were performed and VE was estimated as (1-OR COVID-19vaccinated vs. unvaccinated)x100. Mediation analyses were carried out to offset potential collider variables, particularly, the number of swabs performed after the introduction of pandemic restrictions.

RESULTS

Full-cycle VE against infection decreased from 96% (95% CI: 96, 97) in the Alpha period to 43% (95% CI: 42, 45) in the Omicron period. Booster dose raised the protection in Omicron period to 67% (95% CI: 66, 67). Against the evasive Omicron variant, the protection of the booster dose was 87% (95% CI: 83, 90) for hospitalization and 90% (95% CI: 82, 95) for death. The number of swabs performed was included as a covariate in the adjustments, and the mediation analysis confirmed that it was a strong mediator between vaccination and COVID-19-related outcomes.

CONCLUSIONS

The study suggests that, under similar TNCC settings, mediation analysis and adjustment for number of diagnostic tests should be included, as an effective approach to the challenge of differential testing behavior that may determine substantial selection bias. This correction allowed us to align with results from other studies that show how full-cycle VE against infection was initially high but decreased over time by variant circulation, counterbalanced by booster dose that raised protection across variants and outcome severity.

Real-life effectiveness of COVID-19 vaccine during the Omicron variant-dominant pandemic: how many booster doses do we need?

The surge in coronavirus disease 2019 (COVID-19) caused by the Omicron variants of the severe acute respiratory syndrome coronavirus 2 necessitates researches to inform vaccine effectiveness (VE) and other preventive measures to halt the pandemic. A test-negative case-control study was conducted among adults (age ≥18 years) who were at-risk for COVID-19 and presented for nasopharyngeal real-time polymerase chain reaction testing during the Omicron variant-dominant period in Thailand (1 January 2022-15 June 2022). All participants were prospectively followed up for COVID-19 development for 14 days after the enrolment. Vaccine effectiveness was estimated and adjusted for characteristics associated with COVID-19. Of the 7971 included individuals, there were 3104 cases and 4867 controls. The adjusted VE among persons receiving 2-dose, 3-dose, and 4-dose vaccine regimens for preventing infection and preventing moderate-to-critical diseases were 33%, 48%, 62% and 60%, 74%, 76%, respectively. The VE were generally higher among those receiving the last dose of vaccine within 90 days compared to those receiving the last dose more than 90 days prior to the enrolment. The highest VE were observed in individuals receiving the 4-dose regimen, CoronaVac-CoronaVac-ChAdOx1 nCoV-19-BNT162b2 for both preventing infection (65%) and preventing moderate-to-critical diseases (82%). Our study demonstrated increased VE along with an increase in number of vaccine doses received. Current vaccination programmes should focus on reducing COVID-19 severity and mandate at least one booster dose. The heterologous boosters with viral vector and mRNA vaccines were highly effective and can be used in individuals who previously received the primary series of inactivated vaccine.

Correlates of COVID-19 vaccination intentions and opinions about mandates among four groups of adults in South Africa with distinct vaccine intentions: evidence from a large national survey

INTRODUCTION

Despite a high number of recorded COVID-19 infections and deaths in South Africa, COVID-19 vaccine coverage remained low in March 2022, ten months into the national vaccine roll-out. This study provides evidence on the correlates of vaccine intentions, attitudes towards vaccination and opinions about mandates.

METHODS

We used data from the second COVID-19 Vaccine Survey (CVACS), a telephone survey conducted February-March 2022 among 3,608 South African adults who self-reported not being vaccinated against COVID-19. The survey instrument was designed in consultation with government, policymakers, and civil society; and segmented the sample into four distinct groups with different vaccine intentions (synonymous with vaccine hesitancy levels). Kruskal-Wallis and Mann-Whitney tests were used to examine the sociodemographic characteristics, attitudes and behaviours associated with the different vaccination intentions groups. Thematic coding of responses to open-ended questions elicited insights on reasons for not being vaccinated and attitudes towards mandates.

RESULTS

Intentions to get vaccinated were greater among individuals with lower socio-economic status (Mann-Whitney Z = -11.3, p < 0.001); those believing the vaccine protects against death (Kruskal-Wallis Χ2 = 494, p < 0.001); and those who perceived themselves at risk of COVID-19-related illness (Χ2 = 126, p < 0.01). Vaccine intentions were lower among individuals who believed that the vaccine causes death (Χ2 = 163, p < 0.001); believed that the vaccine is unsafe for the babies of pregnant/breastfeeding mothers, or the chronically ill (Χ2 = 123, p < 0.01); those not trusting government health information about COVID-19 and the COVID-19 vaccine (Kendall's τ = -0.41, p < 0.01); and those in opposition to mandates (τ = 0.35, p < 0.001). Only 25% supported mandates, despite 48% thinking mandates would work well, with 54% citing individual rights as their main reason for mandate opposition.

CONCLUSION

The profile of individuals not vaccinated against COVID-19 as of March 2022 varied markedly by self-reported vaccination intentions, underscoring the importance of tailored demand-creation efforts. This paper highlights several factors which differ significantly across these groups. These findings could inform the design of future vaccination campaigns, potentially increasing their likelihood of success. This is an important policy objective given widespread vaccine hesitancy, and further work is required on this topic. Mandates remain an option to increase coverage but need to be carefully considered given extensive opposition.

Prevalence and risk factors of COVID-19 infection, mortality, and post-infection lung fibrosis in patients with type 2 diabetes: a cross-sectional study

OBJECTIVES

The clinical course of coronavirus disease 2019 (COVID-19) infection is often aggressive, with unfavorable outcomes for those with comorbidities such as type 2 diabetes mellitus (T2DM). We aimed to assess the prevalence and risk factors of COVID-19 infection, mortality, and post-infection lung fibrosis in patients with COVID-19 infection who had T2DM.

METHODS

In this cross-sectional study, we included adult patients with T2DM who attended an endocrinology clinic and underwent testing for COVID-19 infection.

RESULTS

Among 1039 included patients, the mean age was 59.5 ± 11.0 years and 429 (41.3%) were men. Overall, 87.1% of patients had received COVID-19 vaccination and 32.3% had confirmed COVID-19 infection. The COVID-19-related mortality was 3.0% and rate of post-COVID-19 lung fibrosis was 19.1%. Vaccination was associated with lower COVID-19-related mortality (odds ratio [OR]: 0.03, 95% confidence interval [CI]: 0.0-0.3) and post-COVID-19 lung fibrosis risk (OR: 0.3, 95% CI: 0.1-0.9).

CONCLUSION

Patients with T2DM exhibited a high prevalence of COVID-19 infection and associated mortality. However, COVID-19 vaccines were beneficial in reducing the risks of COVID-19-related mortality and post-infection lung fibrosis in these patients. COVID-19 vaccines and boosters are recommended for patients with T2DM. Further studies involving larger study populations are necessary to validate these findings.

Predictors of SARS-CoV-2 Infection and Severe and Lethal COVID-19 after Three Years of Follow-Up: A Population-Wide Study

In this cohort study, the general population of an Italian Province was followed for three years after the start of the pandemic, in order to identify the predictors of SARS-CoV-2 infection and severe or lethal COVID-19. All the National Healthcare System information on biographical records, vaccinations, SARS-CoV-2 swabs, COVID-19 cases, hospitalizations and co-pay exemptions were extracted from 25 February 2020 to 15 February 2023. Cox proportional hazard analysis was used to compute the relative hazards of infection and severe or lethal COVID-19, adjusting for age, gender, vaccine status, hypertension, diabetes, major cardiovascular diseases (CVD), chronic obstructive pulmonary disease (COPD), kidney disease or cancer. Among the 300,079 residents or domiciled citizens, 41.5% had ≥1 positive swabs during the follow-up (which lasted a mean of 932 days). A total of 3.67% of the infected individuals experienced severe COVID-19 (n = 4574) and 1.76% died (n = 2190). Females, the elderly and subjects with diabetes, CVD, COPD, kidney disease and cancer showed a significantly higher risk of SARS-CoV-2 infection. The likelihood of severe or lethal COVID-19 was >90% lower among the youngest, and all comorbidities were independently associated with a higher risk (ranging from +28% to +214%) of both outcomes. Two years after the start of the immunization campaign, the individuals who received ≥2 doses of COVID-19 vaccines still showed a significantly lower likelihood of severe or lethal disease, with the lowest risk observed among subjects who received at least one booster dose.

[Clinical characteristics of children with Omicron variant infection in Chengdu area, China]

OBJECTIVES

To investigate the clinical characteristics of children infected with the Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Chengdu of China.

METHODS

A retrospective analysis was conducted for the clinical data of 226 children who were infected with the Omicron variant of SARS-Cov-2 and were isolated and treated in Chengdu Shelter Hospital from August 28 to September 21, 2022. According to the presence or absence of clinical symptoms, they were divided into two groups: asymptomatic group and mild symptomatic group. The two groups were compared in terms of clinical characteristics, diagnosis and treatment, and prognosis.

RESULTS

Among the 226 children infected with the Omicron variant, 71 (31.4%) were asymptomatic and 155 (68.6%) had mild symptoms. Fever and cough were the most common clinical symptoms, with fever in 95 children (61.3%) and cough in 92 children (59.4%). Of all 226 children, 188 (83.2%) received coronavirus disease 2019 (COVID-19) vaccination. The time to nucleic acid clearance ranged from 6 to 26 days, with a nucleic acid clearance rate of 58.0% (131/226). There were no significant differences among different age groups in sex, early symptoms, clinical typing, nucleic acid re-positive rate, nucleic acid clearance rate, and length of hospital stay (P>0.05). There were no significant differences between the asymptomatic and mild symptomatic groups in age, sex, underlying diseases, COVID-19 vaccination, use of Lianhua Qingwen granules, nucleic acid clearance rate, nucleic acid re-positive rate, and length of hospital stay (P>0.05).

CONCLUSIONS

Children infected with the Omicron variant of SARS-Cov-2 in Chengdu generally have mild clinical symptoms, mainly upper respiratory tract infection, which has little threat to the health of children of different ages, and children tend to have a good overall prognosis.

COVID-19 Vaccination Effectiveness in the General Population of an Italian Province: Two Years of Follow-Up

We carried out a cohort study on the overall population of the province of Pescara, Italy, to assess the real-world effectiveness of SARS-CoV-2 vaccination against infection, severe, or lethal COVID-19, two years after the start of the vaccination campaign. We included all the resident or domiciled subjects, and extracted the official demographic, vaccination, COVID-19, hospital and co-pay exemption datasets from 1 January 2021, up to 15 February 2023. Cox proportional hazards analyses were adjusted for gender, age, diabetes, hypertension, COPD, major cardio- and cerebrovascular events, cancer, and kidney diseases. Throughout the follow-up (466 days on average), 186,676 subjects received greater than or equal to three vaccine doses (of ChAdOx1 nCoV-19, BNT162b2, mRNA-1273, NVX-CoV2373, or JNJ-78436735), 47,610 two doses, 11,452 one dose, and 44,989 none. Overall, 40.4% of subjects were infected with SARS-CoV-2. Of them, 2.74% had severe or lethal (1.30%) COVID-19. As compared to the unvaccinated, the individuals who received greater than or equal to one booster dose showed a ≥85% lower risk of severe or lethal COVID-19. A massive impact of vaccination was found among the elderly: 22.0% of the unvaccinated, infected individuals died, as opposed to less than 3% of those who received greater than or equal to three vaccine doses. No protection against infection was observed, although this finding was certainly influenced by the Italian restriction policies to control the pandemic. Importantly, during the Omicron predominance period, only the group who received at least a booster dose showed a reduced risk of COVID-19-related death.

Clinical Characteristics of Mild Patients with Breakthrough Infection of Omicron Variant in China after Relaxing the Dynamic Zero COVID-19 Policy

For SARS-CoV-2 mutants, the effectiveness of the COVID-19 vaccines is still controversial. In this study, we aimed to investigate the clinical characteristics of Omicron-infected patients who completed primary immunization and booster immunization, respectively, during the rapid propagation of the Omicron variant in China. A total of 932 patients with confirmed SARS-CoV-2 infection from 18 December 2022 to 1 January 2023 were included in this survey by filling out questionnaires online. The enrolled patients were divided into the primary immunization group and the booster immunization group according to their vaccination status. During the whole course of disease, the most frequent symptoms were fever (90.6%), cough (84.3%), weakness (77.4%), headache and dizziness (76.1%), and myalgia (73.9%). Nearly 90% of the patients had symptoms lasting for less than 10 days, and 39.8% of the patients ended the course of the disease in 4-6 days. A total of 58.8% of these patients had a fever with a maximum body temperature of over 38.5 °C. Moreover, 61.4% of the patients had a fever that lasted less than 2 days. There were no obvious differences in initial symptoms, cardinal symptoms, symptom duration time, maximum body temperature, and fever duration time between the two groups of patients. In addition, no significant difference was found in the positive or negative conversion time of SARS-CoV-2 antigen/nucleic acid between the two groups of patients. For mild patients with Omicron breakthrough infection, enhanced immunization has no significant impact on the clinical performance and duration of viral infection compared with primary immunization. The reasons behind the different clinical manifestations of patients with mild symptoms after the breakthrough infection of the Omicron strain are still worth further research. Heterologous vaccination may be a better strategy for enhanced immunization, which can help improve the immune protection ability of the population. Further research should be carried out on vaccines against mutant strains and spectral anti-COVID-19 vaccines.

COVID-19 symptom-onset to diagnosis and diagnosis to treatment intervals are significant predictors of disease progression and hospitalization in high-risk patients: A real world analysis

BACKGROUND

Coronavirus disease (COVID-19) is overwhelming healthcare systems worldwide. This study aimed to elucidate factors that influence disease progression to pneumonia and hospitalization before and after antiviral treatment for COVID-19 in an outpatient setting.

METHODS

A total of 206 high-risk patients with COVID-19 were treated with sotrovimab, remdesivir, and molnupiravir at the Toshiwakai clinic between January 4 and April 30, 2022. Of these, 49 patients visited the Toshiwakai clinic directly and were treated immediately after diagnosis (Toshiwakai-clinic study group). The remaining patients were diagnosed elsewhere, and of these, 102 patients were quarantined at home (health-center study group) and 55 at designated facilities (quarantine-facility study group) before being referred to Toshiwakai clinic. Patients were categorized into those with mild and moderate COVID-19, based on the presence of pneumonia at the initial visit to Toshiwakai clinic.

RESULTS

The symptom-onset-to-diagnosis and diagnosis-to-treatment intervals were significant predictors of moderate disease. Age, dyspnea, and diagnosis-to-treatment interval at the first visit to Toshiwakai clinic were significant predictors for hospitalization even after antiviral treatment. Although the symptom-onset-to-diagnosis interval did not differ among the three study groups, the diagnosis-to-treatment and symptom-onset-to-treatment intervals were significantly longer in the health-center and quarantine-facility study groups than in the Toshiwakai-clinic study group.

CONCLUSION

The symptom-onset-to-diagnosis and diagnosis-to-treatment intervals reflect diagnostic and interventional delays, respectively, which are closely related to the current COVID-19 clinical management protocol. Easy access to the clinics and immediate antiviral treatment after diagnosis may be the best methods to prevent disease progression and hospitalization in high-risk patients.

Comparative analysis of risk factors for COVID-19 mortality before, during and after the vaccination programme in Mexico

OBJECTIVES

The purpose of this study was to compare case fatality rates (CFRs) and odds for mortality by risk factors of patients with COVID-19 in Mexico, before, during and after the implementation of the national COVID-19 vaccination programme.

STUDY DESIGN

A large database including COVID-19 monitoring cases was used to perform an observational retrospective study.

METHODS

The Chi-squared test and multivariate logistic regression analyses were applied to data from COVID-19-positive patients in Mexico. Data were analysed over 3 years, 2020, 2021 and 2022, corresponding with pre-, during and post-vaccination periods. The unadjusted odds ratios and 95% confidence interval were used to estimate the risk factors for COVID-19 mortality in each of the years.

RESULTS

Statistically significant differences in CFR and odds ratio were found in the studied years, favouring postvaccination period. Significant changes in CFR by age, sex and main comorbidities indicated changes in the epidemic dynamics after the implementation of the COVID-19 vaccination campaign. The likelihood of death increased for hospitalised cases and for patients who were middle-aged or older in 2021 and 2022, whereas the odds of death associated with sex and comorbidities remained similar or reduced over the 3 years.

CONCLUSIONS

Implementation of the COVID-19 vaccination programme during 2021 showed positive consequences on CFR. The increased odds of dying in hospitalised patients are likely to be due to the unvaccinated proportion of patients.

COVID-19 Vaccination Did Not Increase the Risk of Potentially Related Serious Adverse Events: 18-Month Cohort Study in an Italian Province

This cohort study on the entire population of an Italian Province assessed the incidence of potentially vaccine-related serious adverse events (PVR-SAEs) by COVID-19 vaccination status. From January 2021 to July 2022, we extracted all deaths and hospitalizations due to several cardiovascular diseases, pulmonary embolism, and deep vein thrombosis from National Healthcare System official data. During the follow-up, 5743 individuals died, and 2097 were hospitalized for PVR-SAEs. Vaccinated subjects (n = 259,821) did not show an increased risk of all-cause death, non-COVID death, or any PVR-SAEs, as compared to the unvaccinated (n = 56,494). These results were consistent across genders, age-classes, vaccine types, and SARS-CoV-2 infection status and did not vary in Cox models adjusting for age, gender, SARS-CoV-2 infection, and selected comorbidities. In the infected population, any dose of vaccine was associated with a lower likelihood of death and PVR-SAE. In the uninfected population, subjects who received one or two doses showed a significantly higher incidence of most outcomes, likely due to a large selection bias introduced by the Italian restriction policies targeting uninfected subjects who received less than three doses. In conclusion, COVID-19 vaccination was not associated with an increase of mortality or selected PVR-SAEs incidence. Further research is warranted to evaluate the long-term safety of COVID-19 vaccines.

SARS-CoV-2-The Role of Natural Immunity: A Narrative Review

BACKGROUND

Both natural immunity and vaccine-induced immunity to COVID-19 may be useful to reduce the mortality/morbidity of this disease, but still a lot of controversy exists.

AIMS

This narrative review analyzes the literature regarding these two immunitary processes and more specifically: (a) the duration of natural immunity; (b) cellular immunity; (c) cross-reactivity; (d) the duration of post-vaccination immune protection; (e) the probability of reinfection and its clinical manifestations in the recovered patients; (f) the comparisons between vaccinated and unvaccinated as to the possible reinfections; (g) the role of hybrid immunity; (h) the effectiveness of natural and vaccine-induced immunity against Omicron variant; (i) the comparative incidence of adverse effects after vaccination in recovered individuals vs. COVID-19-naïve subjects.

MATERIAL AND METHODS

through multiple search engines we investigated COVID-19 literature related to the aims of the review, published since April 2020 through July 2022, including also the previous articles pertinent to the investigated topics.

RESULTS

nearly 900 studies were collected, and 246 pertinent articles were included. It was highlighted that the vast majority of the individuals after suffering from COVID-19 develop a natural immunity both of cell-mediated and humoral type, which is effective over time and provides protection against both reinfection and serious illness. Vaccine-induced immunity was shown to decay faster than natural immunity. In general, the severity of the symptoms of reinfection is significantly lower than in the primary infection, with a lower degree of hospitalizations (0.06%) and an extremely low mortality.

CONCLUSIONS

this extensive narrative review regarding a vast number of articles highlighted the valuable protection induced by the natural immunity after COVID-19, which seems comparable or superior to the one induced by anti-SARS-CoV-2 vaccination. Consequently, vaccination of the unvaccinated COVID-19-recovered subjects may not be indicated. Further research is needed in order to: (a) measure the durability of immunity over time; (b) evaluate both the impacts of Omicron BA.5 on vaccinated and healed subjects and the role of hybrid immunity.

The sources of the Kuznets relationship between the COVID-19 mortality rate and economic performance

This paper discusses the findings of an empirical analysis of the Kuznets, or reverse U-shaped relationship, between the COVID-19 mortality rate and economic performance. In the early stages of economic development, the COVID-19 mortality rate is anticipated to rise with rising economic activity and urbanization. Eventually, the mortality rate decreases at higher economic development levels as people and the government are more capable of investing in disease abatement measures. The quality of political institutions, wealth distribution, urbanization, vaccination rate, and improvements in healthcare systems are hypothesized to affect the COVID-19 mortality rate. Examining this relationship can be effective in understanding the change in the COVID-19 mortality rate at different economic performance stages and in identifying appropriate preventive measures. This study employed the negative binomial regression to model a cross-sectional dataset of 137 countries. Results indicated that the relationship between the per-head gross domestic product (GDP) level and the COVID-19 mortality rate appeared to follow a pattern like the Kuznets curve, implying that changes in institutional quality, healthcare advancements, wealth distribution, urbanization, vaccination rate, and the percentage of the elderly population were significant in explaining the relationship. Improvement of the healthcare system has a notable effect on lowering the COVID-19 mortality rate under more effective government conditions. Additionally, the results suggested that a higher per-head GDP is required to reverse the rising trend of the mortality rate under higher income inequality. Based on these results, preventive measures, and policies to reduce COVID-19 mortalities were recommended in the conclusion section.

COVID-19 Vaccines against Omicron Variant: Real-World Data on Effectiveness

The efficacy of vaccines against coronavirus disease 2019 (COVID-19) has now been well established in phase III clinical trials. However, clinical studies based on real-world data remain critical to assess vaccines effectiveness (VE), especially in specific populations and against variants of concern (VOC). This review presents the principles and methods of VE studies and the main available results on VE of COVID-19 vaccines at the time of Omicron circulation. References for this narrative review were identified through searches of PubMed database up to 13 September 2022. The results of phase III clinical trials have been globally confirmed by VE in real-life studies, including in the elderly. Emergence of VOC Omicron emphasized the importance of booster doses to maintain a high level of protection against severe forms. There are still numerous challenges regarding booster(s) and duration of immunity, particularly in specific subpopulations, and regarding the need for adapted vaccines.

The Vaccine Efficacy Against the SARS-CoV-2 Omicron: A Systemic Review and Meta-Analysis

Background

COVID-19 is a respiratory illness caused by SARS-CoV-2. The most recent variant is Omicron (line B.1.1.529), which was first identified in South Africa in November 2021. The concern with this variant is the ineffectiveness of vaccines currently available. We aim to systematically evaluate the effectiveness of the currently available COVID-19 vaccines and boosters for the Omicron variant.

Methods

We searched the PubMed, Embase, the Cochrane Library and Web of Science databases from inception to June 5th, 2022. Studies that examined the effectiveness of SARS-CoV-2 vaccines against the Omicron variant infection were included. Random-effects model was used to estimate the pooled vaccine effectiveness against the Omicron variant.

Results

A total of 13 studies were included to evaluate the effectiveness of the vaccine against the Omicron variant, and 11 studies were included to compare the effectiveness between the two-dose and three-dose (booster) vaccinations. Full vaccination (two-dose with or without booster) showed a protective effect against the Omicron variant compared to no vaccination (OR = 0.62, 95% CI: 0.56–0.69), while the effectiveness decreased significantly over 6 months after the last dose. The two-dose vaccination plus booster provided better protection against the Omicron variant compared to the two-dose vaccination without booster (OR = 0.60, 95% CI: 0.52–0.68). Additional analysis was performed for the most commonly used vaccines in the United Staes: BNT162b2(Pfizer) (OR = 0.65, 95% CI: 0.52–0.82) and mRNA-1273(Moderna) (OR = 0.67, 95% CI: 0.58–0.88) vaccines in the US, which showed similar effectiveness compared to no vaccination.

Conclusions

The full dose of SARS-CoV-2 vaccination effectively reduces infection from the SARS-CoV-2 Omicron variant; however, the effectiveness wanes over time. The booster vaccine provides additional protection against the Omicron variant.