Heterologous boosting with third dose of coronavirus disease recombinant subunit vaccine increases neutralizing antibodies and T cell immunity against different severe acute respiratory syndrome coronavirus 2 variants

Safety and immunogenicity of heterologous boosting with orally administered aerosolized bivalent adenovirus type-5 vectored COVID-19 vaccine and B.1.1.529 variant adenovirus type-5 vectored COVID-19 vaccine in adults 18 years and older: a randomized, double blinded, parallel controlled trial

Vaccination strategies that can induce a broad spectrum immune response are important to enhance protection against SARS-CoV-2 variants. We conducted a randomized, double-blind and parallel controlled trial to evaluate the safety and immunogenicity of the bivalent (5×1010viral particles) and B.1.1.529 variant (5×1010viral particles) adenovirus type-5 (Ad5) vectored COVID-19 vaccines administrated via inhalation. 451 eligible subjects aged 18 years and older who had been vaccinated with three doses inactivated COVID-19 vaccines were randomly assigned to inhale one dose of either B.1.1.529 variant Ad5 vectored COVID-19 vaccine (Ad5-nCoVO-IH group, N=150), bivalent Ad5 vectored COVID-19 vaccine (Ad5-nCoV/O-IH group, N=151), or Ad5 vectored COVID-19 vaccine (5×1010viral particles; Ad5-nCoV-IH group, N=150). Adverse reactions reported by 37 (24.67%) participants in the Ad5-nCoVO-IH group, 28 (18.54%) in the Ad5-nCoV/O-IH group, and 26 (17.33%) in the Ad5-nCoV-IH group with mainly mild to moderate dry mouth, oropharyngeal pain, headache, myalgia, cough, fever and fatigue. No serious adverse events related to the vaccine were reported. Investigational vaccines were immunogenic, with significant difference in the GMTs of neutralizing antibodies against Omicron BA.1 between Ad5-nCoV/O-IH (43.70) and Ad5-nCoV-IH (29.25) at 28 days after vaccination (P=0.0238). The seroconversion rates of neutralizing antibodies against BA.1 in Ad5-nCoVO-IH, Ad5-nCoV/O-IH, and Ad5-nCoV-IH groups were 56.00%, 59.60% and 48.67% with no significant difference among the groups. Overall, the investigational vaccines were demonstrated to be safe and well tolerated in adults, and was highly effective in inducing mucosal immunities in addition to humoral and cellular immune responses defending against SARS-CoV-2 variants.Trial registration: Chictr.org identifier: ChiCTR2200063996.

Initial COVID-19 severity influenced by SARS-CoV-2-specific T cells imprints T-cell memory and inversely affects reinfection

The immunoprotective components control COVID-19 disease severity, as well as long-term adaptive immunity maintenance and subsequent reinfection risk discrepancies across initial COVID-19 severity, remain unclarified. Here, we longitudinally analyzed SARS-CoV-2-specific immune effectors during the acute infection and convalescent phases of 165 patients with COVID-19 categorized by severity. We found that early and robust SARS-CoV-2-specific CD4+ and CD8+ T cell responses ameliorate disease progression and shortened hospital stay, while delayed and attenuated virus-specific CD8+ T cell responses are prominent severe COVID-19 features. Delayed antiviral antibody generation rather than titer level associates with severe outcomes. Conversely, initial COVID-19 severity imprints the long-term maintenance of SARS-CoV-2-specific adaptive immunity, demonstrating that severe convalescents exhibited more sustained virus-specific antibodies and memory T cell responses compared to mild/moderate counterparts. Moreover, initial COVID-19 severity inversely correlates with SARS-CoV-2 reinfection risk. Overall, our study unravels the complicated interaction between temporal characteristics of virus-specific T cell responses and COVID-19 severity to guide future SARS-CoV-2 wave management.

A superior heterologous prime-boost vaccination strategy against COVID-19: A bivalent vaccine based on yeast-derived RBD proteins followed by a heterologous vaccine

Various vaccines have been challenged by SARS-CoV-2 variants. Here, we reported a yeast-derived recombinant bivalent vaccine (Bivalent wild-type [Wt]+De) based on the wt and Delta receptor-binding domain (RBD). Yeast derived RBD proteins based on the wt and Delta mutant were used as the prime vaccine. It was found that, in the presence of aluminium hydroxide (Alum) and unmethylated CpG-oligodeoxynucleotides (CpG) adjuvants, more cross-protective immunity against SARS-CoV-2 prototype and variants were elicited by bivalent vaccine than monovalent wtRBD or Delta RBD. Furthermore, a heterologous boosting strategy consisting of two doses of bivalent vaccines followed by one dose adenovirus vectored vaccine exhibited cross-neutralization capacity and specific T cell responses against Delta and Omicron (BA.1 and BA.4/5) variants in mice, superior to a homologous vaccination strategy. This study suggested that heterologous prime-boost vaccination with yeast-derived bivalent protein vaccine could be a potential approach to address the challenge of emerging variants.

Dynamic immune landscape in vaccinated-BA.5-XBB.1.9.1 reinfections revealed a 5-month protection-duration against XBB infection and a shift in immune imprinting

BACKGROUND

The impact of previous vaccination on protective immunity, duration, and immune imprinting in the context of BA.5-XBB.1.9.1 reinfection remains unknown.

METHODS

Based on a 2-year longitudinal cohort from vaccination, BA.5 infection and XBB reinfection, several immune effectors, including neutralizing antibodies (Nabs), antibody-dependent cellular cytotoxicity (ADCC), virus-specific T cell immunity were measured to investigate the impact of previous vaccination on host immunity induced by BA.5 breakthrough infection and BA.5-XBB.1.9.1 reinfection.

FINDINGS

In absence of BA.5 Nabs, plasma collected 3 months after receiving three doses of inactivated vaccine (I-I-I) showed high ADCC that protected hACE2-K18 mice from fatality and significantly reduced viral load in the lungs and brain upon BA.5 challenge, compared to plasma collected 12 months after I-I-I. Nabs against XBB.1.9.1 induced by BA.5 breakthrough infection were low at day 14 and decreased to a GMT of 10 at 4 months and 28% (9/32) had GMT ≤4, among whom 67% (6/9) were reinfected with XBB.1.9.1 within 1 month. However, 63% (20/32) were not reinfected with XBB.1.9.1 at 5 months post BA.5 infection. Interestingly, XBB.1.9.1 reinfection increased Nabs against XBB.1.9.1 by 24.5-fold at 14 days post-reinfection, which was much higher than that against BA.5 (7.3-fold) and WT (4.5-fold), indicating an immune imprinting shifting from WT to XBB antigenic side.

INTERPRETATION

Overall, I-I-I can provide protection against BA.5 infection and elicit rapid immune response upon BA.5 infection. Furthermore, BA.5 breakthrough infection effectively protects against XBB.1.9.1 lasting more than 5 months, and XBB.1.9.1 reinfection results in immune imprinting shifting from WT antigen induced by previous vaccination to the new XBB.1.9.1 antigen. These findings strongly suggest that future vaccines should target variant strain antigens, replacing prototype strain antigens.

FUNDING

This study was supported by R&D Program of Guangzhou National Laboratory (SRPG23-005), National Key Research and Development Program of China (2022YFC2604104, 2019YFC0810900), S&T Program of Guangzhou Laboratory (SRPG22-006), and National Natural Science Foundation of China (81971485, 82271801, 81970038), Emergency Key Program of Guangzhou Laboratory (EKPG21-30-3), Zhongnanshan Medical Foundation of Guangdong Province (ZNSA-2020013), and State Key Laboratory of Respiratory Disease (J19112006202304).

Development of an RBD-Fc fusion vaccine for COVID-19

Although the global pandemic of SARS-CoV-2 has passed, there are still regional outbreaks that continue to jeopardize human health. Hence, there is still a great deal of interest in developing an efficient vaccine that can quickly and effectively prevent reemerging outbreaks of SARS-CoV-2. Delta variant was once a dominant strain in the world in 2021, and we first constructed a recombinant RBDdelta-Fc fusion vaccine by coupling the RBD of Delta variant with the human Fc fragment. This Fc fusion strategy increases the immunogenicity of the recombinant RBD vaccine, with a long-lasting high level of IgG antibodies and neutralizing antibodies induced by RBDdelta-Fc vaccine. This RBDdelta-Fc vaccine, as well as the RBD-Fc vaccine prepared in our previously study, could trigger a durable immune effect by the heterologous boosting immunity, and the RBD-Fc induced a quicker humoral immune response than the homologous immunization with inactivated vaccines. In conclusion, the Fc fusion strategy has a significant role in enhancing the immunogenicity of recombinant protein vaccines, thus promising the development of a safe and efficient vaccine for the heterologous boosting against SARS-CoV-2.

Safety, immunogenicity, and efficacy of a modified COVID-19 mRNA vaccine, SW-BIC-213, in healthy people aged 18 years and above: a phase 3 double-blinded, randomized, parallel controlled clinical trial in Lao PDR (Laos)

Background

The mRNA vaccine has demonstrated significant effectiveness in protecting against SARS-CoV-2 during the pandemic, including against severe forms of the disease caused by emerging variants. In this study, we examined safety, immunogenicity, and relative efficacy of a heterologous booster of the lipopolyplex (LPP)-based mRNA vaccine (SW-BIC-213) versus a homologous booster of an inactivated vaccine (BBIBP) in Laos.

Methods

In this phase 3 clinical trial, which was randomized, parallel controlled and double-blinded, healthy adults aged 18 years and above were recruited from the Southern Savannakhet Provincial Hospital and Champhone District Hospital. The primary outcomes were safety and immunogenicity, with efficacy as an exploratory endpoint. Participants who were fully immunized with a two-dose inactivated vaccine for more than 6 months were assigned equally to either the SW-BIC-213 group (25 μg) or BBIBP group. The primary safety endpoint was to describe the safety profile of all participants in each group up to 6 months post-booster immunization. The primary immunogenic outcome was to demonstrate the superiority of the neutralizing antibody response, in terms of geometric mean titers (GMTs) of SW-BIC-213, compared with BBIBP 28 days after the booster dose. The exploratory efficacy endpoint aimed to assess the relative efficacy of SW-BIC-213 compared to BBIBP against virologically confirmed symptomatic COVID-19 over a 6-month period. The trial was registered with ClinicalTrials.gov (NCT05580159).

Findings

Between October 10, 2022, and January 13, 2023, 1200 participants were assigned to SW-BIC-213 group and 1203 participants in the BBIBP group. All adverse reactions observed during the study were tolerable, transient, and resolved spontaneously. Solicited local reactions were the main adverse reactions in both the SW-BIC-213 group (43.8%) and BBIBP group (14.8%) (p < 0.001). Heterologous boosting with SW-BIC-213 induced higher live virus neutralizing antibodies to SARS-CoV-2 wildtype and BA.5 strains with GMTs reaching 750.1 and 192.9 than homologous boosting with BBIBP with GMTs of 131.5 (p < 0.001) and 47.5 (p < 0.001) on day 29. The statistical findings revealed that, following a period of 14-day to 6-month after booster vaccination, the SW-BIC-213 group exhibited a relative vaccine efficacy (VE) of 70.1% (95% CI: 34.2-86.4) against symptomatic COVID-19 when compared to the BBIBP group.

Interpretation

A heterologous booster with the COVID-19 mRNA vaccine SW-BIC-213 manifests a favorable safety profile and proves highly immunogenic and efficacious in preventing symptomatic COVID-19 in individuals who have previously received two doses of inactivated vaccine.

Funding

Shanghai Strategic Emerging Industries Development Special Fund, Biomedical Technology Support Special Project of Shanghai "Science and Technology Innovation Action Plan", Shanghai Municipal Science and Technology Commission.

The 6-Month Antibody Durability of Heterologous Convidecia Plus CoronaVac and Homologous CoronaVac Immunizations in People Aged 18-59 Years and over 60 Years Based on Two Randomized Controlled Trials in China

Previous reports have shown that heterologous boosting with the AD5-vectored COVID-19 vaccine Convidecia based on a primary series of two doses of inactivated vaccine induces increasing immune responses. However, the immune persistence until 6 months after the heterologous prime-boost immunization was limited. Participants were from two single-center, randomized, controlled, observer-blinded trials, which involved individuals of 18-59 years of age and over 60 years of age. Eligible participants who previously primed with one dose or two doses of CoronaVac were stratified and randomly assigned to inoculate a booster dose of Convidecia or CoronaVac. Neutralizing antibodies against a live SARS-CoV-2 prototype virus and Delta and Omicron (B.1.1.529) variants, pseudovirus neutralizing antibodies against Omicron BA.4/5 variants, and anti-SARS-CoV-2 RBD antibodies at month 6 were detected, and the fold decreases and rate difference were calculated by comparing the levels of antibodies at month 6 with the peak levels at month 1. The neutralizing antibody titers against prototype SARS-CoV-2, RBD-specific IgG antibodies, and the Delta variant in the heterologous regimen of the CoronaVac plus Convidecia groups were significantly higher than those of the homologous prime-boost groups. In three-dose regimen groups, the geometric mean titers (GMTs) of neutralizing antibodies against prototype SARS-CoV-2 were 30.6 (95% CI: 25.1; 37.2) in the heterologous boosting group versus 6.9 (95% CI: 5.6; 8.6) in the homologous boosting group (p < 0.001) at month 6 in participants aged 18-59 years, and in the two-dose regimen, the neutralizing antibody GMTs were 8.5 (95% CI: 6.2; 11.7) and 2.7 (2.3 to 3.1) (heterologous regimen group versus CoronaVac regimen group, p < 0.001). Participants aged over 60 years had similar levels of neutralizing antibodies against the prototype, with GMTs of 49.1 (38.0 to 63.6) in the group receiving two doses of CoronaVac plus one dose of Convidecia versus 9.4 (7.7 to 11.4) in the group receiving three doses of CoronaVac (p < 0.001) and 11.6 (8.4 to 16.0) in the group receiving one dose of CoronaVac and one dose of Convidecia versus 3.3 (2.7 to 4.0) in the group receiving two doses of CoronaVac (p < 0.001). Compared with day 14, over sixfold decreases in neutralizing antibody GMTs were observed in the heterologous groups of the three- or two-dose regimen groups of younger and elderly participants, while in the homologous regimen groups, the GMTs of neutralizing antibodies decreased about fivefold in the two age groups. The heterologous prime-boost regimen with two doses of CoronaVac and one dose of Convidecia was persistently more immunogenic than the regimen of the homologous prime-boost with three doses of CoronaVac.

Artificial COVID-19 T-Cell Immunogen

An artificial T-cell immunogen consisting of conserved fragments of different proteins of the SARS-CoV-2 virus and its immunogenic properties were studied in BALB/c mice. To create a T-cell immunogen, we used an approach based on the design of artificial antigens that combine many epitopes from the main proteins of the SARS-CoV-2 virus in the one molecule. The gene of the engineered immunogen protein was cloned as part of the pVAX1 plasmid in two versions: with an N-terminal ubiquitin and without it. The obtained plasmids were analyzed for their ability to provide the synthesis of the immunogen protein in vitro and in vivo. It has been shown that protein product of the created artificial genes is actively processed in HEK293T cells and induces cellular immunity in mice.

The effectiveness of the first dose COVID-19 booster vs. full vaccination to prevent SARS-CoV-2 infection and severe COVID-19 clinical event: a meta-analysis and systematic review of longitudinal studies

Background

The effectiveness of full Coronavirus Disease 2019 (COVID-19) vaccination against COVID-19 wanes over time. This study aimed to synthesize the clinical effectiveness of the first dose of COVID-19 booster by comparing it to the full vaccination.

Methods

Studies in PubMed, Web of Science, Embase, and clinical trials databases were searched from 1 January 2021 to 10 September 2022. Studies were eligible if they comprised general adult participants who were not ever or currently infected with SARS-CoV-2, did not have impaired immunity or immunosuppression, and did not have severe diseases. The seroconversion rate of antibodies to S and S subunits and antibody titers of SARS-CoV-2, frequency, phenotype of specific T and B cells, and clinical events involving confirmed infection, admission to the intensive care unit (ICU), and death were compared between the first booster dose of COVID-19 vaccination group and full vaccination group. The DerSimonian and Laird random effects models were used to estimate the pooled risk ratios (RRs) and corresponding 95% confidence intervals (CIs) for the outcomes of clinical interest. While a qualitative description was mainly used to compare the immunogenicity between the first booster dose of COVID-19 vaccination group and full vaccination group. Sensitivity analysis was used to deal with heterogenicity.

Results

Of the 10,173 records identified, 10 studies were included for analysis. The first dose COVID-19 booster vaccine could induce higher seroconversion rates of antibodies against various SAS-CoV-2 fragments, higher neutralization antibody titers against various SARS-CoV-2 variants, and robust cellular immune response compared to the full vaccination. The risk of SARS-CoV-2 infection, the risk of admission to the ICU, and the risk of death were all higher in the non-booster group than those in the booster group, with RRs of 9.45 (95% CI 3.22-27.79; total evaluated population 12,422,454 vs. 8,441,368; I² = 100%), 14.75 (95% CI 4.07-53.46; total evaluated population 12,048,224 vs. 7,291,644; I² = 91%), and 13.63 (95% CI 4.72-39.36; total evaluated population 12,385,960 vs. 8,297,037; I² = 85%), respectively.

Conclusion

A homogenous or heterogeneous booster COVID-19 vaccination could elicit strong humoral and cellular immune responses to SARS-CoV-2. Furthermore, it could significantly reduce the risk of SARS-CoV-2 infection and severe COVID-19 clinical events on top of two doses. Future studies are needed to investigate the long-term clinical effectiveness of the first booster dose of the COVID-19 vaccine and compare the effectiveness between homogenous and heterogeneous booster COVID-19 vaccination.

Systematic review registration

https://inplasy.com/inplasy-2022-11-0114/, identifier: INPLASY2022110114.

Immunology of SARS-CoV-2 infection and vaccination

Comprehensive elucidation of humoral immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination is critical for understanding coronavirus disease 2019 (COVID-19) pathogenesis in general and developing antibody-based diagnostic and therapeutic strategies specifically. Following the emergence of SARS-CoV-2, significant scientific research has been conducted worldwide using omics, sequencing and immunologic approaches. These studies have been critical to the successful development of vaccines. Here, the current understanding of SARS-CoV-2 immunogenic epitopes, humoral immunity to SARS-CoV-2 structural proteins and non-structural proteins, SARS-CoV-2-specific antibodies, and T-cell responses in convalescents and vaccinated individuals are reviewed. Additionally, we explore the integrated analysis of proteomic and metabolomic data to examine mechanisms of organ injury and identify potential biomarkers. Insight into the immunologic diagnosis of COVID-19 and improvements of laboratory methods are highlighted.

Assessing COVID-19 Vaccine Booster Hesitancy Using the Modified 5C Scale in Zhejiang Province, China: A Cross-Sectional Study

Following the rollout of a booster campaign to promote immunity against COVID-19 in China, this study aimed to assess booster hesitancy among adults who were fully vaccinated with primary doses across Zhejiang Province. Firstly, the modified 5C scale developed by a German research team was assessed for reliability and validity via a pre-survey in Zhejiang Province. Then, a 30-item questionnaire was established to conduct online and offline surveys during 10 November to 15 December 2021. Demographic characteristics and information on previous vaccination experience, vaccine type of primary doses, attitudes towards booster doses and awareness of SARS-CoV-2 infection were collected. Chi-square tests, pairwise comparison and multivariate logistic regression were performed in data analysis. In total, 4039 valid questionnaires were analyzed, with booster hesitancy of 14.81%. Dissatisfaction with previous vaccination experience of primary doses (ORs = 1.771~8.025), less confidence in COVID-19 vaccines (OR = 3.511, 95%CI: 2.874~4.310), younger age compared to the elderly aged 51-60 years old (2.382, 1.274~4.545), lower education level (ORs = 1.707~2.100), weaker awareness of social responsibility of prevention and control of COVID-19 (1.587, 1.353~1.859), inconvenience of booster vaccination (1.539, 1.302~1.821), complacency regarding vaccine efficacy as well as self-health status (1.224, 1.056~1.415) and excessive trade-offs before vaccination (1.184, 1.005~1.398) were positively associated with booster hesitancy. Therefore, intelligent means should be strengthened to optimize vaccination services. More influential experts and other significant figures should be supported to promote timely evidence-based information via various media platforms to reduce public hesitancy and increase booster uptake.

Neutralizing Antibodies as Predictors of Vaccine Breakthrough Infection in Healthcare Workers Vaccinated with or without a Heterologous Booster Dose: A Cohort Study during the Third COVID-19 Wave in Peru

We evaluated neutralizing antibody (NAbs) levels as a protective factor against vaccine breakthrough infection (VBI) in healthcare workers (HCWs) during the third COVID-19 wave in Peru. This retrospective cohort study employed the information from a private laboratory in Lima (Peru) of HCW who received only two BBIBP-CorV vaccines or (additionally) a heterologous booster with BNT162b2. We evaluated the association between the VBI and the levels of NAbs at 21, 90, 180, and 210 days after the BBIBP-CorV second dose. NAbs were calculated with the cPass™ SARS-CoV-2 Neutralization Antibody Detection kit (surrogate virus neutralization test (sVNT)) and the Elecsys^® anti-SARS-CoV-2 S Test. Of the 435 HCW evaluated, 31.72% had an infection previous to vaccination, 68.28% received a booster dose, and 23.21% had a VBI during the third wave. The variables associated with a lower risk of VBI were male sex (aRR: 0.43) and those who had (180 days after BBIBP-CorV inoculation) NAbs levels ≥ 60% (aRR: 0.58) and ≥90% (aRR: 0.59) on cPass™, and ≥500 with Elecsys^® (aRR: 0.58). HCW whose NAbs persisted at higher levels six months after the BBIBP-CorV showed a lower risk of suffering from a VBI during the third COVID-19 wave.

Durability of Vaccine-Induced and Natural Immunity Against COVID-19: A Narrative Review

Vaccines developed against SARS-CoV-2 have proven to be highly effective in preventing symptomatic infection. Similarly, prior infection with SARS-CoV-2 has been shown to provide substantial protection against reinfection. However, it has become apparent that the protection provided to an individual after either vaccination or infection wanes over time. Waning protection is driven by both waning immunity over time since vaccination or initial infection, and the evolution of new variants of SARS-CoV-2. Both antibody and T/B-cells levels have been investigated as potential correlates of protection post-vaccination or post-infection. The activity of antibodies and T/B-cells provide some potential insight into the underlying causes of waning protection. This review seeks to summarise what is currently known about the waning of protection provided by both vaccination and/or prior infection, as well as the current information on the respective antibody and T/B-cell responses.

Safety, immunogenicity and immune-persistence of heterologous prime-boost immunization with BBIBP-CorV and ZF2001 against SARS-CoV-2 in healthy adults aged 18 years or older

BACKGROUND

Because SARS-CoV-2 mutations and immunity wane over time, a third dose of heterologous COVID-19 vaccine is proposed for individuals primed with inactivated COVID-19 vaccine.

RESEARCH DESIGN AND METHODS

We conducted a single-center, open-label trial to assess the safety, immunogenicity, and immune-persistence of a heterologous BBIBP-CorV/ZF2001 prime-boost vaccination in Chinese adults. 480 participants who had been primed with two doses of BBIBP-CorV, received a third dose of ZF2001 after an interval of 3-4, 5-6, or 7-9 months.

RESULTS

The overall incidence of adverse reactions within 30 days after vaccination was 5.83%. No serious adverse reactions were reported. The respective geometric mean titers (GMTs) of neutralizing antibodies for 3-4, 5-6, and 7-9 months groups at baseline were 2.06, 2.02, and 2.10; which increased to 55.42, 63.45, and 62.06 on day 14; then decreased to 17.53, 23.79, and 26.73 on day 30; before finally waning to 8.29, 9.24, and 9.51 on day 180. After the booster, the three groups showed no significant differences in GMTs. GMTs were lower in older participants than younger participants.

CONCLUSIONS

A heterologous BBIBP-CorV/ZF2001 prime-boost vaccination was safe and immunogenic. Prime-boost intervals did not affect the immune response. The immune response was weaker in older adults than younger adults.

CLINICAL TRIAL IDENTIFIER

NCT05205083.

Unglycosylated Soluble SARS-CoV-2 Receptor Binding Domain (RBD) Produced in E. coli Combined with the Army Liposomal Formulation Containing QS21 (ALFQ) Elicits Neutralizing Antibodies against Mismatched Variants

The emergence of novel potentially pandemic pathogens necessitates the rapid manufacture and deployment of effective, stable, and locally manufacturable vaccines on a global scale. In this study, the ability of the Escherichia coli expression system to produce the receptor binding domain (RBD) of the SARS-CoV-2 spike protein was evaluated. The RBD of the original Wuhan-Hu1 variant and of the Alpha and Beta variants of concern (VoC) were expressed in E. coli, and their biochemical and immunological profiles were compared to RBD produced in mammalian cells. The E. coli-produced RBD variants recapitulated the structural character of mammalian-expressed RBD and bound to human angiotensin converting enzyme (ACE2) receptor and a panel of neutralizing SARS-CoV-2 monoclonal antibodies. A pilot vaccination in mice with bacterial RBDs formulated with a novel liposomal adjuvant, Army Liposomal Formulation containing QS21 (ALFQ), induced polyclonal antibodies that inhibited RBD association to ACE2 in vitro and potently neutralized homologous and heterologous SARS-CoV-2 pseudoviruses. Although all vaccines induced neutralization of the non-vaccine Delta variant, only the Beta RBD vaccine produced in E. coli and mammalian cells effectively neutralized the Omicron BA.1 pseudovirus. These outcomes warrant further exploration of E. coli as an expression platform for non-glycosylated, soluble immunogens for future rapid response to emerging pandemic pathogens.

SARS-CoV-2 vaccination-infection pattern imprints and diversifies T cell differentiation and neutralizing response against Omicron subvariants

The effects of different SARS-CoV-2 vaccinations and variant infection histories on imprinting population immunity and their influence on emerging escape mutants remain unclear. We found that Omicron (BA.1) breakthrough infection, regardless of vaccination with two-dose mRNA vaccines (M-M-o) or two-dose inactivated vaccines (I-I-o), led to higher neutralizing antibody levels against different variants and stronger T-cell responses than Delta breakthrough infection after two-dose inactivated vaccine vaccination (I-I-δ). Furthermore, different vaccination-infection patterns imprinted virus-specific T-cell differentiation; M-M-ο showed higher S/M/N/E-specific CD4⁺ T cells and less portion of virus-specific CD45RA⁺CD27^-CD8⁺ T cells by ex vivo assay. Breakthrough infection groups showed higher proliferation and multi-function capacity by in vitro assay than three-dose inactivated vaccine inoculated group (I-I-I). Thus, under wide vaccination coverage, the higher immunogenicity with the Omicron variant may have helped to eliminate the population of Delta variant. Overall, our data contribute to our understanding of immune imprinting in different sub-populations and may guide future vaccination programs.

Immunogenicity, durability, and safety of an mRNA and three platform-based COVID-19 vaccines as a third dose following two doses of CoronaVac in China: A randomised, double-blinded, placebo-controlled, phase 2 trial

BACKGROUND

More effective vaccine candidates against variants of concern as a booster dose are needed in people primed with two-dose inactivated COVID-19 vaccines.

METHODS

This randomised, double-blinded, investigator-initiated phase 2 trial aims to evaluate immunogenicity, durability, and safety of an mRNA vaccine candidate (RQ3013) and three other platform vaccines (an adenovirus-vectored vaccine candidate [ChAdTS-S], a recombinant protein vaccine candidate [ZR202-CoV], and an inactivated vaccine [CoronaVac]) as a booster. 250 eligible volunteers, who had received a prime two-dose CoronaVac (3 to 5 weeks apart) vaccination 100-270 days before, were randomly assigned in a 1:1:1:1:1 ratio to receive a third dose of RQ3013 (30 μg mRNA per 0.15 mL), ChAdTS-S (5×10¹⁰ viral particles per 0.5 mL), ZR202-CoV (25 μg prefusion-stabilized Spike ectodomain trimer per 0.5 mL), CoronaVac (3 μg inactivated CN02 strain of SARS-CoV-2 per 0.5 mL) or placebo (0.5 mL of 0.9% sodium chloride solution) via intramuscular injection into the upper arm at a single clinical site in Kunming, China. Participants, investigators, and immunogenicity laboratory were masked to group assignment. The primary immunogenicity outcomes were geometric mean titres (GMTs) of neutralising antibodies against live SARS-CoV-2 (wild-type, delta and omicron) virus at day 0 (before vaccination), day 7, day 14 and day 28 after vaccination, as analysed in a modified intention-to-treat (mITT) population (all participants who completed their booster doses and had at least one post-dose immunogenicity data). Secondary outcomes include T cell responses against the wild-type and omicron SARS-CoV-2 Spike protein. The primary safety outcome was incidence of adverse events within 14 days after the booster vaccination. This trial is registered with ChiCTR.org.cn, ChiCTR2200057758.

FINDINGS

Between January 1, 2022, and February 28, 2022, 235 eligible participants were enrolled and vaccinated, and the primary analysis included 234 participants. At baseline, neutralising antibodies against wild-type virus, the delta, or omicron variants were low or undetectable in all groups. After the booster vaccination, GMTs of neutralising antibodies ranged from 75.4 (95% confidence interval [CI] 61.4-92.5) in CoronaVac to 950.1 (95% CI 785.4-1149.3) in RQ3013 against live wild-type SARS-CoV-2, and from 8.1 (95% CI: 6.1-10.7) in CoronaVac to 247.0 (95% CI 194.1-314.3) in RQ3013 against the omicron variant at day 14. Immunogenicities of all heterologous regimens were superior to that of homologous regimen in neutralisation against all tested SARS-CoV-2 strains, with RQ3013 showing the highest geometric mean ratios (GMRs) of 12.6, 14.7, and 31.3 against the wild-type, the delta variant and the omicron variant compared to CoronaVac at day 14 post-vaccination, respectively. Durability analysis at day 90 showed that >90% of participants in RQ3013 and ZR202-CoV were seropositive for the omicron variant while ZR202-CoV with adjuvants containing CpG showed a slightly better durability than RQ3013. T cell responses specific to the omicron variant were similar to that of the wild-type, with RQ3013 showing the highest boosting effect. Any solicited injection site or systemic adverse events reported within 14 days after vaccination were most commonly observed in RQ3013 (47/47, 100%), followed by ZR202-CoV (46/47, 97.9%) and ChAdTS-S (43/48, 89.6%), and then CoronaVac (37/46, 80.4%) and placebo (21/47, 44.7%). More than 90% of the adverse events were grade 1 (mild) or 2 (moderate) with a typical resolution time of 3 days. No grade 4 adverse events or serious adverse events were reported by study vaccines.

INTERPRETATION

Although all study vaccines boosted neutralising antibodies with no safety concerns, RQ3013 showed much stronger cross-neutralisation and cellular responses, adding more effective vaccine candidates against the omicron variant.

FUNDING

Yunnan Provincial Science and Technology Department China (202102AA100051 and 202003AC100010), the Double First-class University funding to Yunnan University, National Natural Science Foundation of China (81960116, 82060368 and 82170711), Yunnan Natural Science Foundation (202001AT070085), High-level Health Technical Personnel Project of Yunnan Province (H-2018102) and Spring City Plan: The High-level Talent Promotion and Training Project of Kunming.

Extensive neutralization against SARS-CoV-2 variants elicited by Omicron-specific subunit vaccine as a heterologous booster

To overcome the increased risk of SARS-CoV-2 reinfection or post-vaccination infection caused by the Omicron variant, Omicron-specific vaccines were considered a potential strategy. We reported the increased magnitude and breadth of antibody response against VOCs elicited by post-vaccination Delta and Omicron infection, compared to WT infection without vaccination. Then, in mouse models, three doses of Omicron-RBD immunization elicited comparable neutralizing antibody (NAb) titers with three doses of WT-RBD immunization, but the neutralizing activity was not cross-active. By contrast, a heterologous Omicron-RBD booster following two doses of WT-RBD immunization increased the NAb titers against Omicron by 9-folds than the homologous WT-RBD booster. Moreover, it retains neutralization against both WT and current VOCs. Results suggest that Omicron-specific subunit booster shows its advantages in the immune protection from both WT and current VOCs and that SARS-CoV-2 vaccines including two or more virus lineages might improve the NAb response.

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Post-vaccination SARS-CoV-2 infection can elicit higher and boarder immune response

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A heterologous booster with the Omicron-RBD protein elicits a 9-fold increased NAb

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Heterologous boosting with Omicron enhance the potency and breadth of immune response

Cost-Effectiveness of COVID-19 Sequential Vaccination Strategies in Inactivated Vaccinated Individuals in China

To effectively prevent and control the COVID-19 pandemic, countries have adopted a booster vaccination strategy. This study aimed to estimate the cost-effectiveness of sequential booster COVID-19 vaccination compared to two-dose inactivated vaccination in China from a societal perspective. A Markov model was developed to estimate the cost-effectiveness of sequential vaccination, including two doses of an inactivated vaccine followed by a booster shot of an inactivated vaccine, adenovirus vectored vaccine, protein subunit vaccine, or mRNA vaccine. The incremental effects of a booster shot with an inactivated vaccine, protein subunit vaccine, adenovirus vectored vaccine, and mRNA vaccine were 0.0075, 0.0110, 0.0208, and 0.0249 QALYs and saved costs of US$163.96, US$261.73, US$583.21, and US$724.49, respectively. Under the Omicron virus pandemic, the sequential vaccination among adults and the elderly (aged 60-69, 70-79, over 80) was consistently cost-saving, and a booster shot of the mRNA vaccine was more cost-saving. The results indicate that the sequential vaccination strategy is cost-effective in addressing the COVID-19 pandemic, and improving vaccination coverage among the elderly is of great importance in avoiding severe cases and deaths.

Safety and Immunogenicity of a Heterologous Booster of Protein Subunit Vaccine MVC-COV1901 after Two Doses of Adenoviral Vector Vaccine AZD1222

We report the safety and immunogenicity results in participants administrated with a booster dose of protein subunit vaccine MVC-COV1901 at 12 (Group A) or 24 (Group B) weeks after two doses of AZD1222 (ChAdOx1 nCoV-19). The administration of the MVC-COV1901 vaccine as a booster dose in both groups was generally safe. There were no serious adverse events related to the intervention as adverse events reported were "mild" or "moderate" in nature. In subjects fully vaccinated with two doses of AZD1222, waning antibody immunity was apparent within six months of the second dose of AZD1222. At one month after the MVC-COV1901 booster dose, those who were vaccinated within 12 weeks after the last AZD1222 dose (Group A) had anti-SARS-CoV-2 spike IgG antibody titers and neutralizing antibody titers which were 14- and 6.5-fold increased, respectively, when compared to the titer levels on the day of the booster dose. On the other hand, fold-increase a month post-booster in people who had a booster 24 weeks after the last AZD1222 dose (Group B) were 19.5 and 14.0 times for anti-SARS-CoV-2 spike IgG antibody titers and neutralizing antibody titers, respectively. Among those who were vaccinated within 12 weeks after the last AZD1222 dose, we also observed 5.2- and 5.6-fold increases in neutralizing titer levels against ancestral strain and Omicron variant pseudovirus after the booster dose, respectively. These results support the use of MVC-COV1901 as a heterologous booster for individuals vaccinated with AZD1222. Furthermore, regardless of the dosing schedule, the combination of AZD1222 primary series and MVC-COV1901 booster can be cost-effective and suitably applied to low- and middle-income countries (LMIC).

Heterologous booster with inhaled Adenovirus vector COVID-19 vaccine generated more neutralizing antibodies against different SARS-CoV-2 variants

The rapid widespread Omicron subvariant BA.5 of SARS-CoV-2 has become a potential imminent pandemic threat, but available vaccines lack high efficacy against this subvariant. Thus, it is urgent to find highly protective vaccination strategies within available SARS-CoV-2 vaccines. Here, by using a SARS-CoV-2 pseudovirus neutralization assay, we demonstrated that the aerosol inhalation of adenoviral vector COVID-19 vaccine after two dose of inactivated vaccine (I-I-Ad5) led to higher levels of neutralizing antibodies against D614G strain (2041.00[95% CI, 1243.00-3351.00] vs 249.00[149.10-415.70]), Omicron BA.2 (467.10[231.00-944.40] vs 72.21[39.31-132.70]), BA.2.12.1(348.5[180.3-673.4] vs 53.17[31.29-90.37]), BA.2.13 (410.40[190.70-883.3] vs 48.48[27.87-84.32]), and BA.5 (442.40 vs 56.08[35.14-89.51]) than three inactivated vaccine doses (I-I-I). Additionally, the level of neutralizing antibodies against BA.5 induced by I-I-Ad5 was 2.41-fold higher than those boosted by a third dose of RBD subunit vaccine (I-I-S) (p = 0.1308). The conventional virus neutralizing assay confirmed that I-I-Ad5 induced higher titer of neutralizing antibodies than I-I-I (116.80[84.51-161.5] vs 4.40[4.00-4.83]). In addition, I-I-Ad5 induced higher, but later, anti-RBD IgG and IgA in plasma than I-I-I. Our study verified that mucosal immunization with aerosol inhalation of adenoviral vector COVID-19 vaccine may be an effective strategy to control the probable wave of BA.5 pandemic in addition to two inactivated vaccines.

Lower vaccine-acquired immunity in the elderly population following two-dose BNT162b2 vaccination is alleviated by a third vaccine dose

Understanding the impact of age on vaccinations is essential for the design and delivery of vaccines against SARS-CoV-2. Here, we present findings from a comprehensive analysis of multiple compartments of the memory immune response in 312 individuals vaccinated with the BNT162b2 SARS-CoV-2 mRNA vaccine. Two vaccine doses induce high antibody and T cell responses in most individuals. However, antibody recognition of the Spike protein of the Delta and Omicron variants is less efficient than that of the ancestral Wuhan strain. Age-stratified analyses identify a group of low antibody responders where individuals ≥60 years are overrepresented. Waning of the antibody and cellular responses is observed in 30% of the vaccinees after 6 months. However, age does not influence the waning of these responses. Taken together, while individuals ≥60 years old take longer to acquire vaccine-induced immunity, they develop more sustained acquired immunity at 6 months post-vaccination. A third dose strongly boosts the low antibody responses in the older individuals against the ancestral Wuhan strain, Delta and Omicron variants.

Impact of COVID-19 pandemic on the epidemiology of STDs in China: based on the GM (1,1) model

Background

COVID-19 and Sexually Transmitted Diseases (STDs) are two very important diseases. However, relevant researches about how COVID-19 pandemic has impacted on the epidemiological trend of STDs are limited in China. This study aimed to analyze the impact of COVID-19 on STDs in China and proposed relevant recommendations to be used in bettering health.

Methods

The incidence of HIV infection, syphilis and gonorrhea in China from 2008 to 2020 were collected. Grey Model (1,1) were established to predict the incidence of STDs with the incidence data of these three STDs from 2013 to 2018 considering the impact of policies in China, respectively. We then calculated the predictive incidence of each STD in 2019, 2020 and 2021 by the established Model. And we estimated the extent of the impact of COVID-19 on the epidemiological changes of STDs by analyzing the difference between the absolute percentage error (APE) of the predictive incidence and actual rate in 2019 and 2020.

Results

The incidence of HIV infection and syphilis showed a trend of increase from 2008 to 2019 in China, but that for gonorrhea was fluctuant. Of note, the incidence of these three STDs decreased significantly in 2020 compared with that in 2019. The APE of HIV infection, syphilis and gonorrhea in 2020 (20.54%, 15.45% and 60.88%) were about 7 times, 4 times and 2 times of that in 2019 (2.94%, 4.07% and 30.41%). The incidence of HIV infection, syphilis and gonorrhea would be 5.77/100,000, 39.64/100,000 and 13.19/100,000 in 2021 based on our model.

Conclusions

The epidemiological trend of STDs in China was significant influenced by COVID-19 pandemic. It is important to balance the control of COVID-19 and timely management of STDs during the COVID-19 epidemic to prevent or reduce the poor outcome among COVID-19 patients with STDs. New management strategies on STDs, such as leveraging social media, online medical care, rapid self-testing, timely diagnosis and treatment guarantee and balance of medical resources for STDs management should be adapted in the context of the long-term effects of COVID-19.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07496-y.