Comparison of the Effectiveness and Safety of Heterologous Booster Doses with Homologous Booster Doses for SARS-CoV-2 Vaccines: A Systematic Review and Meta-Analysis

SCB-2019 protein vaccine as heterologous booster of neutralizing activity against SARS-CoV-2 Omicron variants after immunization with other COVID-19 vaccines

We assessed the non-inferiority of homologous boosting compared with heterologous boosting with the recombinant protein vaccine, SCB-2019, in adults previously immunized with different COVID-19 vaccines. Three equal cohorts (N ~ 420) of Philippino adults (18-80 years) previously immunized with Comirnaty, CoronaVac or Vaxzevria COVID-19 vaccines were randomized 1:1 to receive homologous or heterologous (SCB-2019) boosters. Neutralizing antibodies against prototype SARS-CoV-2 (Wuhan-Hu-1) were measured in all participants and against Delta variant and Omicron sub-lineages in subsets (30‒50 per arm) 15 days after boosting. Participants recorded solicited adverse events for 7 days and unsolicited and serious adverse events until Day 60. Prototype SARS-CoV-2 neutralizing responses on Day 15 after SCB-2019 were statistically non-inferior to homologous Vaxzevria boosters, superior to CoronaVac, but lower than homologous Comirnaty. Neutralizing responses against Delta and Omicron BA.1, BA.2, BA.4 and BA.5 variants after heterologous SCB-2019 were higher than homologous CoronaVac or Vaxzevria, but lower than homologous Comirnaty. Responses against Omicron BF.7, BQ.1.1.3, and XBB1.5 following heterologous SCB-2019 were lower than after homologous Comirnaty booster but significantly higher than after Vaxzevria booster. SCB-2019 reactogenicity was similar to CoronaVac or Vaxzevria, but lower than Comirnaty; most frequent events were mild/moderate injection site pain, headache and fatigue. No vaccine-related serious adverse events were reported. Heterologous SCB-2019 boosting was well tolerated and elicited neutralizing responses against all tested SARS-COV-2 viruses including Omicron BA.1, BA.2, BA.4, BA.5, BF.7, BQ.1.1.3, and XBB1.5 sub-lineages that were non-inferior to homologous boosting with CoronaVac or Vaxzevria, but not homologous Comirnaty booster.

Worldwide SARS-CoV-2 Omicron variant infection: Emerging sub-variants and future vaccination perspectives

The coronavirus disease 2019 (COVID-19) pandemic has sparked widespread concern globally, particularly with the Omicron variant and its sub-lineages emerging as the predominant cause of infection for nearly two years. Taiwan's successful containment of COVID-19, underscored by broad vaccine coverage, the utilization of anti-viral therapeutics, and timely response strategies, has resulted in reduced excess mortality. Moreover, there is a crucial need for a phased exit strategy, balancing efforts to curtail disease transmission with the mitigation of socioeconomic impacts from rigorous measures. In this review, we examined the evolution and the epidemiological landscape of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron sub-variants in Taiwan as well as other countries of the world. We also critically evaluated the effectiveness of COVID-19 vaccines against various SARS-CoV-2 variants. Additionally, we addressed the advantages of heterologous immunization strategies, fluctuations in neutralizing antibody titers, and complexities in establishing protective correlates among swiftly mutating viral variants.

Equal Maintenance of Anti-SARS-CoV-2 Antibody Levels Induced by Heterologous and Homologous Regimens of the BNT162b2, ChAdOx1, CoronaVac and Ad26.COV2.S Vaccines: A Longitudinal Study Up to the 4th Dose of Booster

Several technological approaches have been used to develop vaccines against COVID-19, including those based on inactivated viruses, viral vectors, and mRNA. This study aimed to monitor the maintenance of anti-SARS-CoV-2 antibodies in individuals from Brazil according to the primary vaccination regimen, as follows: BNT162b2 (group 1; 22) and ChAdOx1 (group 2; 18). Everyone received BNT162b2 in the first booster while in the second booster CoronaVac, Ad26.COV2.S, or BNT162b2. Blood samples were collected from 2021 to 2023 to analyze specific RBD (ELISA) and neutralizing antibodies (PRNT50). We observed a progressive increase in anti-RBD and neutralizing antibodies in each subsequent dose, remaining at high titers until the end of follow-up. Group 1 had higher anti-RBD antibody titers than group 2 after beginning the primary regimen, with significant differences after the 2nd and 3rd doses. Group 2 showed a more expressive increase after the first booster with BNT162B2 (heterologous booster). Group 2 also presented high levels of neutralizing antibodies against the Gamma and Delta variants until five months after the second booster. In conclusion, the circulating levels of anti-RBD and neutralizing antibodies against the two variants of SARS-CoV-2 were durable even five months after the 4th dose, suggesting that periodic booster vaccinations (homologous or heterologous) induced long-lasting immunity.

Heterologous versus homologous COVID-19 booster vaccinations for adults: systematic review with meta-analysis and trial sequential analysis of randomised clinical trials

BACKGROUND

To combat coronavirus disease 2019 (COVID-19), booster vaccination strategies are important. However, the optimal administration of booster vaccine platforms remains unclear. Herein, we aimed to assess the benefits and harms of three or four heterologous versus homologous booster regimens.

METHODS

From November 3 2022 to December 21, 2023, we searched five databases for randomised clinical trials (RCT). Reviewers screened, extracted data, and assessed bias risks independently with the Cochrane risk-of-bias 2 tool. We conducted meta-analyses and trial sequential analyses (TSA) on our primary (all-cause mortality; laboratory confirmed symptomatic and severe COVID-19; serious adverse events [SAE]) and secondary outcomes (quality of life [QoL]; adverse events [AE] considered non-serious). We assessed the evidence with the GRADE approach. Subgroup analyses were stratified for trials before and after 2023, three or four boosters, immunocompromised status, follow-up, risk of bias, heterologous booster vaccine platforms, and valency of booster.

RESULTS

We included 29 RCTs with 43 comparisons (12,538 participants). Heterologous booster regimens may not reduce the relative risk (RR) of all-cause mortality (11 trials; RR 0.86; 95% CI 0.33 to 2.26; I2 0%; very low certainty evidence); laboratory-confirmed symptomatic COVID-19 (14 trials; RR 0.95; 95% CI 0.72 to 1.25; I2 0%; very low certainty); or severe COVID-19 (10 trials; RR 0.51; 95% CI 0.20 to 1.33; I2 0%; very low certainty). For safety outcomes, heterologous booster regimens may have no effect on SAE (27 trials; RR 1.15; 95% CI 0.68 to 1.95; I2 0%; very low certainty) but may raise AE considered non-serious (20 trials; RR 1.19; 95% CI 1.08 to 1.32; I2 64.4%; very low certainty). No data on QoL was available. Our TSAs showed that the cumulative Z curves did not reach futility for any outcome.

CONCLUSIONS

With our current sample sizes, we were not able to infer differences of effects for any outcomes, but heterologous booster regimens seem to cause more non-serious AE. Furthermore, more robust data are instrumental to update this review.

Effectiveness of different booster vaccine combinations against SARS-CoV-2 during a six-month follow-up in Mexico and Argentina

Introduction

Given the limited number of patients in Latin America who have received a booster dose against the COVID-19, it remains crucial to comprehend the effectiveness of different vaccine combinations as boosters in real-world scenarios. This study aimed to assess the real-life efficacy of seven different vaccine schemes against COVID-19, including BNT162b2, ChAdOx1-S, Gam-COVID-Vac, and CoronaVac as primary schemes with either BNT162b2 or ChAdOx1-S as booster vaccines.

Methods

In this multicentric longitudinal observational study, participants from Mexico and Argentina were followed for infection and SARS-CoV-2 Spike 1-2 IgG antibodies during their primary vaccination course and for 185 days after the booster dose.

Results

A total of 491 patients were included, and the booster dose led to an overall increase in the humoral response for all groups. Patients who received BNT162b2 exhibited the highest antibody levels after the third dose, while those with primary Gam-COVID-Vac maintained a higher level of antibodies after six months. Infection both before vaccination and after the booster dose, and Gam-COVIDVac + BNT162b2 combination correlated with higher antibody titers.

Discussion

The sole predictor of infection in the six-month follow-up was a prior COVID-19 infection before the vaccination scheme, which decreased the risk of infection, and all booster vaccine combinations conveyed the same amount of protection.

Immunogenicity and safety of boosting with a recombinant two-component SARS-CoV-2 vaccine: two randomized, parallel-controlled, phase 2 studies

BACKGROUND

Recombinant protein vaccines are vital for broad protection against SARS-CoV-2 variants. This study assessed ReCOV as a booster in two Phase 2 trials.

RESEARCH DESIGN AND METHODS

Study-1 involved subjects were randomized (1:1:1) to receive 20 μg ReCOV, 40 μg ReCOV, or an inactivated vaccine (COVILO®) in the United Arab Emirates. Study-2 participating individuals were randomized (1:1:1) to receive 20 μg ReCOV (pilot batch, ReCOV HA), 20 μg ReCOV (commercial batch, ReCOV TC), or 30 μg BNT162b2 (COMIRNATY®) in the Philippines. The primary immunogenicity objectives was to compare the geometric mean titer (GMT) and seroconversion rate (SCR) of neutralizing antibodies induced by one ReCOV booster dose with those of inactivated vaccine and BNT162b2, respectively, at 14 days post-booster.

RESULTS

Heterologous ReCOV booster doses were safe and induced comparable immune responses to inactivated vaccines and BNT162b2 against Omicron variants and the prototype. They showed significant advantages in cross-neutralization against multiple SARS-CoV-2 variants, surpassing inactivated vaccines and BNT162b2, with good immune persistence.

CONCLUSIONS

Heterologous ReCOV boosting was safe and effective, showing promise in combating COVID-19. The study highlights ReCOV's potential for enhanced protection, supported by strong cross-neutralization and immune persistence.

CLINICAL TRIAL REGISTRATION

Study-1, www.clinicaltrials.gov, identifier is NCT05323435; Study-2, www.clinicaltrials.gov, identifier is NCT05084989.

Assessing acceptability of the fourth dose against COVID-19 among Chinese adults: A population-based survey

Coronavirus disease 2019 (COVID-19) has wreaked havoc across the globe for approximately three years. Vaccination is a key factor to ending this pandemic, but its protective effect diminishes over time. A second booster dose at the right time is needed. To explore the willingness to receive the fourth dose of the COVID-19 vaccine and its influencing factors, we commenced a national, cross-sectional and anonymous survey in mainland China among people aged 18 and above from October 24 to November 7, 2022. A total of 3,224 respondents were eventually included. The acceptance rate of the fourth dose was 81.1% (95% CI: 79.8-82.5%), while it was 72.6% (95% CI: 71.1-74.2%) for a heterologous booster. Confidence in current domestic situation and the effectiveness of previous vaccinations, and uncertainty about extra protection were the main reasons for vaccine hesitancy. Perceived benefit (aOR = 1.29, 95% CI: 1.159-1.40) and cues to action (aOR = 1.73, 95% CI: 1.60-1.88) were positively associated with the vaccine acceptance, whereas perceived barriers (aOR = 0.78, 95% CI: 0.72-0.84) and self-efficacy (aOR = 0.79, 95% CI: 0.71-0.89) were both negatively associated with it. Additionally, sex, age, COVID-19 vaccination history, time for social media, and satisfaction with the government's response to COVID-19 were also factors affecting vaccination intention. Factors influencing the intention of heterologous booster were similar to the above results. It is of profound theoretical and practical significance to clarify the population's willingness to vaccinate in advance and explore the relevant influencing factors for the subsequent development and promotion of the fourth-dose vaccination strategies.

Sex Differences in Serious Adverse Events Reported Following Booster Doses of COVID-19 Vaccination in Thailand: A Countrywide Nested Unmatched Case-Control Study

A booster dose of a COVID-19 vaccine has been proven effective in restoring vaccine effectiveness and is currently recommended for use in some populations at risk of severe COVID-19 infection. Since sex differences in adverse events are significant in response to the vaccines, the safety of booster selection must be studied to avoid serious adverse events (SAE), such as life-threatening diseases. First, this study aimed to identify sex differences in SAE incidences using a prospective cohort design. Second, a nested unmatched case-control study was used to identify factors associated with reported SAE within 30 days after the booster shot. Multivariable logistic regression indicated the adjusted odds ratio by accounting for host and vaccine variables, thus, policy effects. The findings confirmed that SAE was rare and that age-sex-dominated disease classifications differed. Specific to SAE following the booster dose, we found that females aged 12-40 had a higher risk of being reported with SAE than males of the same age, while males over 50 had a higher risk than females. Other risk factors identified were the presence of metabolic syndrome and the use of certain vaccine brands. Mechanisms could be explained by individual host responses rather than the vaccines' direct effect. Therefore, SAE could be preventable by age-sex-specific vaccine selection, post-vaccination precautions, and early symptom detection. Future vaccine development should aim to limit host-specific reactogenicity for safety concerns.

Longitudinal study of disease severity and external factors in cognitive failure after COVID-19 among Indonesian population

The COVID-19 infection is assumed to induce cognitive failure. Identifying the relationship between COVID-19, the effect of vaccination and medication, and accommodating non-COVID-19 factors to cognitive failure is essential. This study was conducted in Indonesia from September 2021 to January 2023. Demographic information, clinical data, comorbidities, vaccination, and medication during COVID-19 were obtained, as well as a 6-month cognitive assessment with Cognitive Failures Questionnaire/CFQ, Fatigue Severity Score, and Generalized Anxiety Disorder (GAD-7). A Structural Equation Model explains the relationship between potential predictors and cognitive failure. The average score of CFQ after 6 months was 45.6 ± 23.1 out of 100. The severity of the disease, which was associated with vaccination status, age, previous infection, and unit of treatment (p < 0.05), was not related to cognitive failure (p = 0.519), although there is a significant direct impact of worst vaccination status to cognitive failure(p < 0.001). However, age, fatigue, and current anxiety were associated with higher cognitive failure (p < 0.001), although comorbidities and recent headaches were not significant in other models (p > 0.05). This study concludes that cognitive failure after COVID-19 is a multifactorial event and does not solely depend on COVID-19 severity. It is crucial to re-address the factors related to the long-term efficacy of vaccination and medication and focus on non-health factors affecting cognitive failure.Trial Registration: NCT05060562.

Superior Boosting of Neutralizing Titers Against Omicron SARS-CoV-2 Variants by Heterologous SCB-2019 Vaccine vs a Homologous Booster in CoronaVac-Primed Adults

BACKGROUND

We compared homologous and heterologous boosting in adults in the Philippines primed with 2 or 3 doses of CoronaVac, with recombinant protein vaccine, SCB-2019.

METHODS

CoronaVac-immunized adults (18-72 years) received a homologous or heterologous full or half dose SCB-2019 booster. We assessed all neutralizing antibody (NAb) responses against prototype SARS-CoV-2 after 15 days and NAb against SARS-CoV-2 Delta and Omicron variants in subsets (30‒50 per arm). Participants recorded adverse events.

RESULTS

In 2-dose CoronaVac-primed adults prototype NAb geometric mean titers (GMT) were 203 IU/mL (95% confidence interval [CI], 182-227) and 939 IU/mL (95% CI, 841-1049) after CoronaVac and SCB-2019 boosters; the GMT ratio (4.63; 95% CI, 3.95-5.41) met predefined noninferiority and post-hoc superiority criteria. After 3-dose CoronaVac-priming prototype NAb GMTs were 279 IU/mL (95% CI, 240-325), 1044 IU/mL (95% CI, 898-1213), and 668 IU/mL (95% CI, 520-829) following CoronaVac, full and half-dose SCB-2019 boosters, respectively. NAb GMT ratios against Delta and Omicron comparing SCB-2019 with CoronaVac were all greater than 2. Mild to moderate reactogenicity was evenly balanced between groups. No vaccine-related serious adverse events were reported.

CONCLUSIONS

Full or half dose SCB-2019 boosters were well tolerated with superior immunogenicity than homologous CoronaVac, particularly against newly emerged variants. Clinical Trials Registration. NCT05188677.

A two-arm analysis of the immune response to heterologous boosting of inactivated SARS-CoV-2 vaccines

Several vaccine programs were introduced during the COVID-19 pandemic, which included inactivated virus, DNA viral vectors and mRNA vaccines. Booster programs are recommended, especially for those in high-risk groups. However, many of these booster programs involve heterologous vaccines. This study enrolled volunteers who first received two full-dose CoronaVac vaccinations before receiving heterologous boosters with DNA- and/or mRNA-vaccines for an additional 2 doses (n = 40) or an additional 3 doses (n = 16). Our results showed no difference in side effects, neutralizing antibodies, or T-cell responses for any of the heterologous vaccination programs. However, the neutralizing capacity and IFN-γ responses against the Omicron variant in volunteers who received 4 or 5 doses were improved. Polarization of peripheral memory T cells after stimulation in all booster groups with Omicron peptide showed an increased trend of naïve and central memory phenotypes of both CD4+ and CD8+ T cells, suggesting that exposure to Omicron antigens will drive T cells into a lymphoid resident T cell phenotype. Our data support a continuous vaccination program to maximize the effectiveness of immunity, especially in people at high risk. Furthermore, the number of boosting doses is important for maintaining immunity.

Vaccine-induced SARS-CoV-2 antibody response: the comparability of S1-specific binding assays depends on epitope and isotype discrimination

Background

Quantification of the SARS-CoV-2-specific immune response by serological immunoassays is critical for the management of the COVID-19 pandemic. In particular, neutralizing antibody titers to the viral spike (S) protein have been proposed as a correlate of protection (CoP). The WHO established the First International Standard (WHO IS) for anti-SARS-CoV-2 immunoglobulin (Ig) (NIBSC 20/136) to harmonize binding assays with the same antigen specificity by assigning the same unitage in binding antibody units (BAU)/ml.

Method

In this study, we analyzed the S1-specific antibody response in a cohort of healthcare workers in Germany (n = 76) during a three-dose vaccination course over 8.5 months. Subjects received either heterologous or homologous prime-boost vaccination with ChAdOx1 nCoV-19 (AstraZeneca) and BNT162b2 (Pfizer-BioNTech) or three doses of BNT162b2. Antibodies were quantified using three anti-S1 binding assays (ELISA, ECLIA, and PETIA) harmonized to the WHO IS. Serum levels of neutralizing antibodies were determined using a surrogate virus neutralization test (sVNT). Binding assays were compared using Spearman's rank correlation and Passing-Bablok regression.

Findings

All assays showed good correlation and similar antibody kinetics correlating with neutralizing potential. However, the assays show large proportional differences in BAU/ml. ECLIA and PETIA, which detect total antibodies against the receptor- binding domain (RBD) within the S1 subunit, interact similarly with the convalescent plasma-derived WHO IS but differently with vaccine serum, indicating a high sensitivity to the IgG/IgM/IgA ratio.

Conclusion

All three binding assays allow monitoring of the antibody response in COVID-19-vaccinated individuals. However, the assay-specific differences hinder the definition of a common protective threshold in BAU/ml. Our results highlight the need for the thoughtful use of conversion factors and consideration of method-specific differences. To improve the management of future pandemics and harmonize total antibody assays, we should strive for reference material with a well-characterized Ig isotype composition.

Effectiveness of various COVID-19 vaccine regimens among 10.4 million patients from the National COVID Cohort Collaborative during Pre-Delta to Omicron periods - United States, 11 December 2020 to 30 June 2022

OBJECTIVE

This study reports the vaccine effectiveness (VE) of COVID-19 vaccine regimens in the United States, based on the National COVID Cohort Collaborative (N3C) database.

METHODS

Data from 10.4 million adults, enrolled in the N3C from 11 December 2020 to 30 June 2022, were analyzed. VE against infection and death outcomes were evaluated across 13 vaccine regimens in recipient cohorts during the Pre-Delta, Delta, and Omicron periods. VE was estimated as (1-odds ratio) × 100% by multivariate logistic regression, using the unvaccinated cohort as reference.

RESULTS

Natural immunity showed a highly protective effect (70.33%) against re-infection, but the mortality risk among the unvaccinated population was increased after re-infection; vaccination following infection reduced the risk of re-infection and death. mRNA-1273 full vaccination plus mRNA-1273 booster showed the highest anti-infection effectiveness (47.59%) (95% CI, 46.72-48.45) in the overall cohort. In the type 2 diabetes cohort, VE against infection was highest with BNT162b2 full vaccination plus mRNA-1273 booster (61.19%) (95% CI, 53.73-67.75). VE against death was also highest with BNT162b2 full vaccination plus mRNA-1273 booster (89.56%) (95% CI, 85.75-92.61). During the Pre-Delta period, all vaccination regimens showed an anti-infection effect; during the Delta period, only boosters, mixed vaccines, and Ad26.COV2.S vaccination exhibited an anti-infection effect; during the Omicron period, none of the vaccine regimens demonstrated an anti-infection effect. Irrespective of the variant period, even a single dose of mRNA vaccine offered protection against death, thus demonstrating survival benefit, even in the presence of infection or re-infection. Similar patterns were observed in patients with type 2 diabetes.

CONCLUSIONS

Although the anti-infection effect declined as SARS-CoV-2 variants evolved, all COVID-19 mRNA vaccines had sustained effectiveness against death. Vaccination was crucial for preventing re-infection and reducing the risk of death following SARS-CoV-2 infection.

Assessing potential surge of COVID-19 cases and the need for booster vaccine amid emerging SARS-CoV-2 variants in Indonesia: A modelling study from West Java

Objectives

Primary and booster vaccinations are crucial in COVID-19 control. This study aimed to assess the minimum booster coverage to hamper potential surge of COVID-19 cases in 2023 in Indonesia, a low-resource setting country.

Methods

We used a modified SEIR compartment model to assess different scenarios in booster coverage across West Java population: 35%, 50%, and 70%. We fitted the model, then we calculated the potential active cases in 2023 if each scenario was met before 2022 ends. A heat map of predicted cases from various booster coverages and time frames was produced and matched with vaccination rate's function to determine feasible time frames.

Results

A minimum of 70% booster coverage in West Java is needed to reduce 90% of potential COVID-19 cases and avert possible surge in 2023. The booster doses should be distributed before February 2023 to achieve its optimum preventive effect. Delays in achieving minimum booster coverage is acceptable, but higher booster coverage will be required.

Conclusions

For better COVID-19 control in Indonesia, booster vaccination is warranted, as presented by a case study in West Java. Sufficient vaccine supplies, infrastructure, and healthcare workers should be ensured to support a successful booster vaccination program.

Evaluation of SARS-CoV-2 infection risks after primary vaccination with BNT162b2, BBIBP-CorV, or ChAdOx1-nCOV-19 and after homologous and heterologous booster vaccinations with these vaccines and evaluation of SARS-CoV-2 reinfection profiles

Background

The emergence of SARS-CoV-2 variants has significantly increased the number of cases of COVID-19 among vaccinated individuals, raising concerns about the effectiveness of current vaccines. The aim of this study was to analyze the SARS-CoV-2 infection risks after primary vaccination with BNT162b2, BBIBP-CorV, or ChAdOx1-nCOV-19 and after homologues and heterologous booster vaccinations with these vaccines, as well as the profiles of reinfected patients.

Methods

We analyzed retrospectively 1082 patients vaccinated or unvaccinated with BNT162b2, BBIBP-CorV, and/or ChAdOx1nCoV-19 vaccines to determine their SARS-CoV2 infection statuses using the reverse transcription-polymerase chain reaction (RT-PCR) in addition to their clinical features. The infection risks of patients receiving the different vaccine regimens were compared using multivariate logistic regression analysis, comparing the adjusted OR of a positive COVID-19 test result.

Results

Among 596 vaccinated patients, 53%(n = 286) tested positive for SARS-CoV-2 and 57%(n = 310) tested negative. Among positive cases, 10 were reinfection cases. The risk of SARS-CoV-2 infection was 1.6 (adj. OR) for patients who received one dose compared with those who received two doses (95% CI = 1.3-1.8; p < 0.01).The risk was 2.6 (adj. OR) for patients who received one dose compared with those who received three doses (95%CI = 2.1-3.3; p < 0.01), and 1.6 (adj. OR) for patients who received two doses compared with those who received three doses (95% CI = 1.3-2; p < 0.01). The patients who received two doses that were heterologous to that of the primary vaccine had the lowest risk of infection. Booster vaccinations (third dose) significantly reduced the number of positive cases with an acceptable safety profile. Higher cycle-threshold (Ct) values (indicative of viral load) were observed in vaccinated patients, whereas low Ct values were observed in unvaccinated patients.

Conclusion

A complete cycle of vaccination with homologous vaccines or heterologous vaccines resulted in an acceptable reduction in SARS-CoV-2 infection. Further, vaccination was associated with a reduction in viral load.

Novel receptor, mutation, vaccine, and establishment of coping mode for SARS-CoV-2: current status and future

Since the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its resultant pneumonia in December 2019, the cumulative number of infected people worldwide has exceeded 670 million, with over 6.8 million deaths. Despite the marketing of multiple series of vaccines and the implementation of strict prevention and control measures in many countries, the spread and prevalence of SARS-CoV-2 have not been completely and effectively controlled. The latest research shows that in addition to angiotensin converting enzyme II (ACE2), dozens of protein molecules, including AXL, can act as host receptors for SARS-CoV-2 infecting human cells, and virus mutation and immune evasion never seem to stop. To sum up, this review summarizes and organizes the latest relevant literature, comprehensively reviews the genome characteristics of SARS-CoV-2 as well as receptor-based pathogenesis (including ACE2 and other new receptors), mutation and immune evasion, vaccine development and other aspects, and proposes a series of prevention and treatment opinions. It is expected to provide a theoretical basis for an in-depth understanding of the pathogenic mechanism of SARS-CoV-2 along with a research basis and new ideas for the diagnosis and classification, of COVID-19-related disease and for drug and vaccine research and development.

Effectiveness of homologous or heterologous immunization regimens against SARS-CoV-2 after two doses of inactivated COVID-19 vaccine: A systematic review and meta-analysis

We aimed to evaluate the effectiveness or efficacy of heterologous or homologous COVID-19 vaccine regimens against COVID-19-related outcomes after primary immunization with two doses of CoronaVac or Sinopharm COVID-19 vaccines. PubMed, EMBASE, Web of Science, and Cochrane Library databases were searched up to 31 October 2022. The primary measure was vaccine effectiveness against COVID-19 infection with homologous or heterologous booster. The results showed heterologous and homologous booster significantly improved effectiveness against COVID-19 infection compared to primary immunization. The effectiveness against COVID-19 infection was 89.19% (95%CI 78.49, 99.89) for heterologous mRNA vaccine booster, 87.00% (95%CI 82.14, 91.85) for non-replicating vector vaccine booster, 69.99% (95%CI 52.16, 87.82) for homologous booster, and 51.48% (95%CI 41.75, 61.21) for two doses of inactivated vaccine. Homologous and heterologous regimens were also effective against SARS-CoV-2 variants, and more evidence is still needed to confirm our findings.

Comparative effectiveness of heterologous third dose vaccine schedules against severe covid-19 during omicron predominance in Nordic countries: population based cohort analyses

OBJECTIVE

To investigate the comparative vaccine effectiveness of heterologous booster schedules (ie, three vaccine doses) compared with primary schedules (two vaccine doses) and with homologous mRNA vaccine booster schedules (three vaccine doses) during a period of omicron predominance.

DESIGN

Population based cohort analyses.

SETTING

Denmark, Finland, Norway, and Sweden, 27 December 2020 to 31 December 2022.

PARTICIPANTS

All adults aged ≥18 years who had received at least a primary vaccination schedule of AZD1222 (Oxford-AstraZeneca) or monovalent SARS-CoV-2 wild type (ancestral) strain based mRNA vaccines BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna), in any combination.

MAIN OUTCOME MEASURES

The main outcome measure was country combined risks of covid-19 related hospital admission and death with covid-19 and additional outcomes of covid-19 related admission to an intensive care unit and SARS-CoV-2 infection. During a period of omicron predominance, these outcomes were compared in those who received a heterologous booster versus primary schedule (matched analyses) and versus those who received a homologous mRNA vaccine booster (weighted analyses). Follow-up was for 75 days from day 14 after the booster dose; comparative vaccine effectiveness was calculated as 1-risk ratio.

RESULTS

Across the four Nordic countries, 1 086 418 participants had received a heterologous booster schedule of AZD1222+BNT162b2 or mRNA-1273 and 2 505 093 had received a heterologous booster schedule of BNT162b2+mRNA-1273. Compared with the primary schedule only (two doses), the vaccine effectiveness of heterologous booster schedules comprising AZD1222+BNT162b2 or mRNA-1273 and BNT162b2+mRNA-1273 was 82.7% (95% confidence interval 77.1% to 88.2%) and 81.5% (78.9% to 84.2%) for covid-19 related hospital admission and 95.9% (91.6% to 100.0%) and 87.5% (82.5% to 92.6%) for death with covid-19, respectively. Homologous mRNA booster schedules were similarly associated with increased protection against covid-19 related hospital admission (≥76.5%) and death with covid-19 (≥84.1%) compared with previous primary course vaccination only. When a heterologous booster schedule was compared with the homologous booster schedule, vaccine effectiveness was 27.2% (3.7% to 50.6%) for AZD1222+BNT162b2 or mRNA-1273 and 23.3% (15.8% to 30.8%) for BNT162b2+mRNA-1273 schedules against covid-19 related hospital admission and 21.7% (-8.3% to 51.7%) and 18.4% (-15.7% to 52.5%) against death with covid-19, respectively.

CONCLUSION

Heterologous booster schedules are associated with increased protection against severe, omicron related covid-19 outcomes compared with primary course schedules and homologous booster schedules.

The Prospective COVID-19 Post-Immunization Serological Cohort in Munich (KoCo-Impf): Risk Factors and Determinants of Immune Response in Healthcare Workers

Antibody studies analyze immune responses to SARS-CoV-2 vaccination and infection, which is crucial for selecting vaccination strategies. In the KoCo-Impf study, conducted between 16 June and 16 December 2021, 6088 participants aged 18 and above from Munich were recruited to monitor antibodies, particularly in healthcare workers (HCWs) at higher risk of infection. Roche Elecsys^® Anti-SARS-CoV-2 assays on dried blood spots were used to detect prior infections (anti-Nucleocapsid antibodies) and to indicate combinations of vaccinations/infections (anti-Spike antibodies). The anti-Spike seroprevalence was 94.7%, whereas, for anti-Nucleocapsid, it was only 6.9%. HCW status and contact with SARS-CoV-2-positive individuals were identified as infection risk factors, while vaccination and current smoking were associated with reduced risk. Older age correlated with higher anti-Nucleocapsid antibody levels, while vaccination and current smoking decreased the response. Vaccination alone or combined with infection led to higher anti-Spike antibody levels. Increasing time since the second vaccination, advancing age, and current smoking reduced the anti-Spike response. The cumulative number of cases in Munich affected the anti-Spike response over time but had no impact on anti-Nucleocapsid antibody development/seropositivity. Due to the significantly higher infection risk faced by HCWs and the limited number of significant risk factors, it is suggested that all HCWs require protection regardless of individual traits.

COVID-19 Booster Dose Coverage and Hesitancy among Older Adults in an Urban Slum and Resettlement Colony in Delhi, India

BACKGROUND

The high prevalence of vaccine booster hesitancy, with the concomitant waning of humoral vaccine or hybrid immunity, and the emergence of SARS-CoV-2 variants of concern can accentuate COVID-19 morbidity and mortality. The study objective was to ascertain the COVID-19 vaccination coverage, including the administration of precaution (booster) dose vaccination, among the older population in an urban slum and resettlement colony population in Delhi, India.

METHODS

We conducted a cross-sectional survey in an urban resettlement colony, slum, and village cluster in the Northeast district of Delhi among residents aged ≥50 years.

RESULTS

A total of 2217 adults (58.28%) had obtained a COVID-19 booster (precaution) dose vaccine, 1404 (36.91%) had received two doses of a COVID-19 vaccine without booster dose, 121 (3.18%) were unvaccinated, while 62 (1.63%) participants received a single dose. Based on adjusted analysis, older adults (>65 years), higher education, and higher per-capita income were statistically significant predictors of booster dose vaccination.

CONCLUSIONS

More than four in ten adults in an urban slum and resettlement colony in Delhi lacked COVID-19 booster dose vaccination despite high rates of double-dose vaccination (~95%). Public health programming should provide an enhanced focus on reducing complacency with renewed prioritization for improving ease of access to COVID-19 vaccination services, particularly in underserved areas.

COVID-19 Vaccination Coverage among 42,565 Adults Amid the Spread of Omicron Variant in Beijing, China

Vaccines against coronavirus disease 2019 (COVID-19) have been in use for over two years, but studies that reflect real-world vaccination coverage and demographic determinants are lacking. Using a multistage stratified random cluster sampling method, we planned to directly explore vaccination coverage and the demographic determinants of different doses of COVID-19 vaccines in Beijing, especially in older populations. All 348 community health service centers in 16 districts were involved. We performed multivariable logistic regression analyses to identify demographic determinants of different coverage rates via adjusted odds ratios (aORs) and 95% CIs. Of the 42,565 eligible participants, the total vaccination coverage rates for ≥1 dose, ≥2 doses, ≥3 doses, and 4 doses were 93.3%, 91.6%, 84.9%, and 13.0%, respectively, but decreased to 88.1%, 85.1%, 76.2%, and 3.8% in the older population. Among all participants, younger (aOR = 1.77, 95% CI: 1.60–1.95), male (aOR = 1.15, 95% CI: 1.06–1.23), and better-educated residents (high school and technical secondary school aOR = 1.58, 95% CI: 1.43–1.74; bachelor’s degree aOR = 1.53, 95% CI: 1.37–1.70) were more likely to be fully vaccinated. People who lived in rural areas (aOR = 1.45, 95% CI: 1.31–1.60) and held the new rural cooperative health insurance (aOR = 1.37, 95% CI: 1.20–1.57) established a higher rate of full vaccination coverage. No history of chronic disease was positively associated with a higher coverage rate (aOR = 1.81, 95% CI: 1.66–1.97). Occupation also affected vaccination coverage. Demographic factors influencing the rate of vaccination with at least one or three doses were consistent with the results above. Results remained robust in a sensitivity analysis. Given the highly transmissible variants and declining antibody titers, accelerating the promotion of booster vaccination coverage, especially in high-risk groups such as the elderly, is a top priority. For all vaccine-preventable diseases, rapidly clarifying vaccine-hesitant populations, clearing barriers, and establishing a better immune barrier can effectively safeguard people’s lives and property and coordinate economic development with epidemic prevention and control.

Why Some People Are Hesitant to Receive COVID-19 Boosters: A Systematic Review

As the COVID-19 pandemic continues and transitions to an endemic stage, booster vaccines will play an important role in personal and public health. However, convincing people to take boosters continues to be a key obstacle. This study systematically analyzed research that examined the predictors of COVID-19 booster vaccine hesitancy. A search of PubMed, Medline, CINAHL, Web of Science, and Scopus uncovered 42 eligible studies. Globally, the average COVID-19 booster vaccination hesitancy rate was 30.72%. Thirteen key factors influencing booster hesitancy emerged from the literature: demographics (gender, age, education, income, occupation, employment status, ethnicity, and marital status), geographical influences (country, region, and residency), adverse events, perceived benefit/efficacy, perceived susceptibility, perceived severity, prior history of COVID-19 infection, vaccination status, vaccination recommendations, health status, knowledge and information, skepticism/distrust/conspiracy theories, and vaccine type. Vaccine communication campaigns and interventions for COVID boosters should focus on factors influencing booster confidence, complacency, and convenience.

Effectiveness of full (booster) COVID-19 vaccination against severe outcomes and work absenteeism in hospitalized patients with COVID-19 during the Delta and Omicron waves in Greece

AIM

We estimated vaccine effectiveness (VE) of full (booster) vaccination against severe outcomes in hospitalized COVID-19 patients during the Delta and Omicron waves.

METHODS

The study extended from November 15, 2021 to April 17, 2022. Full vaccination was defined as a primary vaccination plus a booster ≥ 6 months later.

RESULTS

We studied 1138 patients (mean age: 66.6 years), of whom 826 (72.6 %) had > 1 comorbidity. Of the 1138 patients, 75 (6.6 %) were admitted to intensive care unit (ICU), 64 (5.6 %) received mechanical ventilation, and 172 (15.1 %) died. There were 386 (33.9 %) fully vaccinated, 172 (15.1 %) partially vaccinated, and 580 (51 %) unvaccinated patients. Unvaccinated patients were absent from work for longer periods compared to partially or fully vaccinated patients (mean absence of 20.1 days versus 12.3 and 17.3 days, respectively; p-value = 0.03). Compared to unvaccinated patients, fully vaccinated patients were less likely to be admitted to ICU [adjusted relative risk (ARR: 0.49; 95 % CI: 0.29-0.84)], mechanically ventilated (ARR: 0.43; 95 % CI: 0.23-0.80), and die (ARR: 0.57; 95 % CI: 0.42-0.78), while they were hospitalized for significantly shorter periods (ARR: 0.79; 95 % CI: 0.70-0.89). The adjusted full VE was 48.8 % (95 % CI: 42.7 %-54.9 %) against ICU admission, 55.4 % (95 % CI: 52.0 %-56.2 %) against mechanical ventilation, and 22.6 % (95 % CI: 7.4 %-34.8 %) against death. For patients with ≥ 3 comorbidities, VE was 56.2 % (95 % CI: 43.9 %-67.1 %) against ICU admission, 60.2 % (95 % CI: 53.7 %-65.4 %) against mechanical ventilation, and 43.9 % (95 % CI: 19.9 %-59.7 %) against death.

CONCLUSIONS

Full (booster) COVID-19 vaccination conferred protection against severe outcomes, prolonged hospitalization, and prolonged work absenteeism.

Timing of last COVID-19 vaccine dose and SARS-CoV-2 breakthrough infections in fully (boosted) vaccinated healthcare personnel

AIM

To estimate the incidence, timing and severity of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) breakthrough infections in fully vaccinated healthcare personnel (HCP).

METHODS

In total, 6496 fully vaccinated HCP were analysed prospectively from 15^th November 2021 to 17^th April 2022. Full coronavirus disease 2019 (COVID-19) vaccination was defined as a complete primary vaccination series followed by a booster dose at least 6 months later.

RESULTS

Overall, 1845 SARS-CoV-2 breakthrough infections occurred (28.4 episodes per 100 HCP), of which 1493 (80.9%) were COVID-19 cases and 352 (19.1%) were asymptomatic infections. Of the 1493 HCP with COVID-19, four were hospitalized for 3-6 days (hospitalization rate among HCP with COVID-19: 0.3%). No intubations or deaths occurred. SARS-CoV-2 breakthrough infections occurred at a mean of 16.2 weeks after the last vaccine dose. Multi-variable regression analyses showed that among the 1845 HCP with a breakthrough infection, the administration of a COVID-19 vaccine dose ≥16.2 weeks before the infection was associated with increased likelihood of developing COVID-19 rather than asymptomatic SARS-CoV-2 infection [odds ratio (OR) 1.58, 95% confidence interval (CI) 1.01-2.46; P=0.045] compared with administering a vaccine dose later. The likelihood of developing COVID-19 compared with asymptomatic infection increased by 7% weekly after the last COVID-19 vaccine dose (OR 1.07, 95% CI 1.03-1.11; P=0.001).

CONCLUSION

SARS-CoV-2 breakthrough infections are common among fully (boosted) vaccinated HCP. However, full COVID-19 vaccination offered considerable protection against hospitalization. These findings may contribute to defining the optimal timing for booster vaccinations. More efficient COVID-19 vaccines that will also confer protection against SARS-CoV-2 infection are needed urgently.

Exploring the Protective Effect of Food Drugs against Viral Diseases: Interaction of Functional Food Ingredients and SARS-CoV-2, Influenza Virus, and HSV

A complex network of processes inside the human immune system provides resistance against a wide range of pathologies. These defenses form an innate and adaptive immunity, in which certain immune components work together to counteract infections. In addition to inherited variables, the susceptibility to diseases may be influenced by factors such as lifestyle choices and aging, as well as environmental determinants. It has been shown that certain dietary chemical components regulate signal transduction and cell morphologies which, in turn, have consequences on pathophysiology. The consumption of some functional foods may increase immune cell activity, defending us against a number of diseases, including those caused by viruses. Here, we investigate a range of functional foods, often marketed as immune system boosters, in an attempt to find indications of their potential protective role against diseases caused by viruses, such as the influenza viruses (A and B), herpes simplex virus (HSV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in some cases mediated by gut microbiota. We also discuss the molecular mechanisms that govern the protective effects of some functional foods and their molecular constituents. The main message of this review is that discovering foods that are able to strengthen the immune system can be a winning weapon against viral diseases. In addition, understanding how the dietary components function can aid in the development of novel strategies for maintaining human bodily health and keeping our immune systems strong.

Intentions of Patients with Hypertension to Receive a Booster Dose of the COVID-19 Vaccine: A Cross-Sectional Survey in Taizhou, China

COVID-19 patients with hypertension have increased hospital complications and mortality rates. Moreover, these patients also have lower antibody titers after receiving the coronavirus disease (COVID-19) vaccine. Therefore, patients with hypertension should receive a COVID-19 vaccine booster. To promote the uptake of COVID-19 vaccine booster among hypertensive patients, this study investigated patients’ willingness and factors that influence patients with hypertension to receive the COVID-19 vaccine booster. From July 2021 to August, 410 patients with hypertension were surveyed. Overall, 76.8% of patients were willing to receive the COVID-19 vaccine booster, as 82.7% of patients without comorbidities and 72.7% of patients with comorbidities were willing to receive the vaccine booster. The main factors that influenced the willingness of patients with hypertension to receive a booster dose were the preventive effect of the vaccine (χ2 = 52.827, p < 0.05), vaccine safety (χ2 = 42.423, p < 0.05), vaccine knowledge (χ2 = 7.831, p < 0.05), presence of comorbidities (χ2 = 4.862, p < 0.05), disease control (χ2 = 5.039, p < 0.05), and antihypertensive treatments (χ2 = 12.565, p < 0.05). This study’s findings highlight the need to promote knowledge about booster vaccination among patients and health management. These measures would improve patients’ willingness and knowledge about the vaccine and their health status, which are the main factors that influence patients’ intention to receive booster vaccines.