Safety and efficacy of COVID-19 prime-boost vaccinations: Homologous BBIBP-CorV versus heterologous BNT162b2 boosters in BBIBP-CorV-primed individuals

Vaccination Strategies: Mixing Paths Versus Matching Tracks

Vaccination strategies play a pivotal role in achieving broad and robust immune protection. With the advent of new technologies and challenges posed by emerging infectious diseases such as SARS-CoV-2, evaluating the efficacy of homologous (matching tracks) and heterologous (mixing paths) vaccination regimens is critical. This article explores mechanistic insights and empirical evidence on the benefits and limitations of these approaches.

Humoral and cellular immune durability of different COVID-19 vaccine platforms following homologous/heterologous boosters: one-year post vaccination

Introduction

The durability of Hybrid immunity induced by natural infection and/or COVID-19 vaccines and evidence supporting further booster vaccination are crucial factors for pandemic response, yet remain poorly understood.

Methods

We measured the durability of immune response and neutralizing capacity of antibodies following Homologous/Heterologous vaccination by mRNA-based vaccines (Pfizer-BioNTech BNT162b2) or (Moderna mRNA-1273) and viral vector-based vaccines (ChAdox1 nCoV-19-Oxford-AstraZeneca) in infected and non-infected patients. We also evaluated the long-lasting specific humoral IgG levels and T-cell immunity of the Memory CD8 cells.

Results

We found that heterologous prime boosters led to significantly higher IgG antibody levels)9.09(than homologous boosters)5.236) one year after vaccination. We measured SARS-CoV-2 anti-S IgG antibodies and then assessed their neutralizing capacity to inhibit the receptor-binding domain (RBD) of the SARS-CoV-2 wild-type strain and omicron B.1.1.529/BA.2 variants from binding to the ACE2 receptors. The heterologous regiment demonstrated superior ACE2-binding inhibition and consistently had higher mean ACE2-receptor binding inhibition across all dose regimens without the need for further doses. The CD8+ T cells producing IFN-γ to various COVID-19 vaccine dose regimens were evaluated. We found that robust T cell mediated immune responses were preserved and largely induced by a heterogeneous vaccination eliciting a significantly higher CD8+ T cells IFN-γ response in 100% of vaccinees regardless of previous natural infection. Indeed, the difference between infected and naïve groups was less pronounced suggesting a reduced infection-related response.

Discussion

Across three layers of evidence, this study showed that heterologous vaccination provides longer-lasting immunity than homologous doses, regardless of prior natural infection.

Effect of Homologous and Heterologous Booster in COVID-19 Vaccination

Background: COVID-19 became a global health crisis in early 2020, and the way out of the crisis was the rapid development of vaccines by Sinopharm, Pfizer, and Sputnik, among others, which played a crucial role in controlling the pandemic. Therefore, this study aims to investigate the long-term immune response by measuring the levels of anti-S1 IgG antibodies induced by homologous and heterologous vaccination regimens. Methods: We investigated the titer of the anti-S1 IgG antibody produced for the viral surface antigen 3, 6 months after the second dose, before the third dose, and 1, 3, and 6 months after the third dose. Results: Anti-S1 IgG antibody levels significantly increased three/six months after the second dose and following the booster in individuals without prior COVID-19 infection who received all three homologous vaccine doses. The group that initially responded poorly to Sinopharm showed a significant and sustained increase after receiving the Pfizer booster. Additionally, prior SARS-CoV-2 infection between primary and booster vaccination boosted anti-S1 antibody titers in all individuals, regardless of the vaccine used. The highest vaccine efficacy was observed during the primary vaccination period and declined over time, especially during the omicron-dominant period. Conclusions: The results suggest that while homologous and heterologous booster doses can significantly enhance anti-S1 IgG antibody levels, prior SARS-CoV-2 infection and the type of vaccine administered influence the duration and magnitude of the immune response.

Immunogenicity and real-world effectiveness of COVID-19 vaccines in Lebanon: Insights from primary and booster schemes, variants, infections, and hospitalization

In this study, we conducted a case-control investigation to assess the immunogenicity and effectiveness of primary and first booster homologous and heterologous COVID-19 vaccination regimens against infection and hospitalization, targeting variants circulating in Lebanon during 2021-2022. The study population comprised active Lebanese military personnel between February 2021 and September 2022. Vaccine effectiveness (VE) against laboratory-confirmed SARS-CoV-2 infection and associated hospitalization was retrospectively determined during different variant-predominant periods using a case-control study design. Vaccines developed by Sinopharm, Pfizer, and AstraZeneca as well as Sputnik V were analyzed. Prospective assessment of humoral immune response, which was measured based on the SARS-CoV-2 antispike receptor binding domain IgG titer, was performed post vaccination at various time points, focusing on Sinopharm and Pfizer vaccines. Statistical analyses were performed using IBM SPSS and GraphPad Prism. COVID-19 VE remained consistently high before the emergence of the Omicron variant, with lower estimates during the Delta wave than those during the Alpha wave for primary vaccination schemes. However, vaccines continued to offer significant protection against infection. VE estimates consistently decreased for the Omicron variant across post-vaccination timeframes and schemes. VE against hospitalization declined over time and was influenced by the variant. No breakthrough infections progressed to critical or fatal COVID-19. Immunogenicity analysis revealed that the homologous Pfizer regimen elicited a stronger humoral response than Sinopharm, while a heterologous Sinopharm/Pfizer regimen yielded comparable results to the Pfizer regimen. Over time, both Sinopharm's and Pfizer's primary vaccination schemes exhibited decreased humoral immunity titers, with Pfizer being a more effective booster than Sinopharm. This study, focusing on healthy young adults, provides insights into VE during different pandemic waves. Continuous research and monitoring are essential for understanding vaccine-mediated immune responses under evolving circumstances.

Heterologous booster vaccination enhances antibody responses to SARS-CoV-2 by improving Tfh function and increasing B-cell clonotype SHM frequency

Heterologous prime-boost has broken the protective immune response bottleneck of the COVID-19 vaccines. however, the underlying mechanisms have not been fully elucidated. Here, we investigated antibody responses and explored the response of germinal center (GC) to priming with inactivated vaccines and boosting with heterologous adenoviral-vectored vaccines or homologous inactivated vaccines in mice. Antibody responses were dramatically enhanced by both boosting regimens. Heterologous immunization induced more robust GC activation, characterized by increased Tfh cell populations and enhanced helper function. Additionally, increased B-cell activation and antibody production were observed in a heterologous regimen. Libra-seq was used to compare the differences of S1-, S2- and NTD-specific B cells between homologous and heterologous vaccination, respectively. S2-specific CD19+ B cells presented increased somatic hypermutations (SHMs), which were mainly enriched in plasma cells. Moreover, a heterologous booster dose promoted the clonal expansion of B cells specific to S2 and NTD regions. In conclusion, the functional role of Tfh and B cells following SARS-CoV-2 heterologous vaccination may be important for modulating antibody responses. These findings provide new insights for the development of SARS-CoV-2 vaccines that induce more robust antibody response.

Safety and immunogenicity of COReNAPCIN, a SARS-CoV-2 mRNA vaccine, as a fourth heterologous booster in healthy Iranian adults: A double-blind, randomized, placebo-controlled, phase 1 clinical trial with a six-month follow-up

The recurrent COVID-19 infection, despite global vaccination, highlights the need for booster doses. A heterologous booster has been suggested to enhance immunity and protection against emerging variants of concern of the SARS-CoV-2 virus. In this report, we aimed to assess the safety, and immunogenicity of COReNAPCIN, as a fourth booster dose after three doses of inactivated vaccines.

METHODS

The study was conducted as a double-blind, randomized, placebo-controlled phase 1 clinical trial of the mRNA-based vaccine candidate, COReNAPCIN. The vaccine was injected as a heterologous booster in healthy Iranian adults aged 18-50 who had previously received three doses of inactivated SARS-CoV-2 vaccines. In the study, 30 participants were randomly assigned to receive either COReNAPCIN in two different doses (25 µg and 50 µg) or placebo. The vaccine candidate contained mRNA encoding the complete sequence of the pre-fusion stabilized Spike protein of SARS-CoV-2, formulated within lipid nanoparticles. The primary endpoint was safety and the secondary objective was humoral immunogenicity until 6 months post-vaccination. The cellular immunogenicity was pursued as an exploratory outcome.

RESULTS

COReNAPCIN was well tolerated in vaccinated individuals in both doses with no life-threatening or other serious adverse events. The most noticeable solicited adverse events were pain at the site of injection, fatigue and myalgia. Regarding the immunogenicity, despite the seroprevalence of SARS-CoV-2 antibodies due to the vaccination history for all and previous SARS-CoV-2 infection for some participants, the recipients of 25 and 50 µg COReNAPCIN, two weeks post-vaccination, showed 6·6 and 8·1 fold increase in the level of anti-RBD, and 11·5 and 21·7 fold increase in the level of anti-spike antibody, respectively. The geometric mean virus neutralizing titers reached 10.2 fold in the 25 µg group and 8.4 fold in 50 µg group of pre-boost levels. After 6 months, the measured anti-spike antibody concentration still maintains a geometric mean fold rise of 2.8 and 6.3, comparing the baseline levels in 25 and 50 µg groups, respectively. Additionally, the significant increase in the spike-specific IFN-ϒ T-cell response upon vaccination underscores the activation of cellular immunity.

CONCLUSION

COReNAPCIN booster showed favorable safety, tolerability, and immunogenicity profile, supporting its further clinical development (Trial registration: IRCT20230131057293N1).

Safety and immunogenicity of heterologous boosting with a bivalent SARS-CoV-2 mRNA vaccine (XBB.1.5/BQ.1) in Chinese participants aged 18 years or more: A randomised, double-blinded, active-controlled phase 1 trial

Continuous emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants urges the development of new vaccines. We assessed the safety and immunogenicity of SYS6006.32, a bivalent vaccine (XBB.1.5/BQ.1), in healthy adults who had received SARS-CoV-2 primary vaccination. In a randomised, double-blinded, active-controlled trial, 200 participants were randomised to receive one dose of SYS6006.32 (N = 100) or a prototype-based, monovalent control vaccine SYS6006 (N = 100). Adverse events (AEs) were collected through the study. Immunogenicity was assessed by live-virus neutralising antibody (Nab) and pseudovirus Nab. 61 (61.0 %) and 60 (60.0 %) participants reported AE in the SYS6006.32 and SYS6006 groups, respectively. Most AEs were grade 1 or 2. Pain and fever were the most common injection-site and systemic AEs, respectively. No serious AEs were observed. SYS6006.32 heterologous boosting induced robust Nab responses against BA.5, XBB.1.5 and EG.5 with live-virus Nab geometric mean titres (GMTs) increased by 17.1-, 34.0-, and 48.0-fold, and pseudovirus Nab GMTs increased by 12.2-, 32.0-, and 35.1-fold, respectively, 14 days after vaccination. SYS6006.32 demonstrated a superior immunogenicity to SYS6006. SYS6006.32 also induced robust pseudovirus Nab responses against XBB.1.16, XBB.2.3, and BA.2.86, with GMTs 3- to 6-fold higher than those induced by SYS6006. In conclusion, SYS6006.32 showed good safety profile and superior immunogenicity to the monovalent vaccine SYS6006.

Immunogenicity of Two Doses of BNT162b2 mRNA COVID-19 Vaccine with a ChAdOx1-S Booster Dose among Navy Personnel in Mexico

Booster doses of the SARS-CoV-2 vaccine have been recommended to improve and prolong immunity, address waning immunity over time, and contribute to the control of the COVID-19 pandemic. A heterologous booster vaccine strategy may offer advantages over a homologous approach. To compare the immunogenicity of two doses of BNT162b2 mRNA COVID-19 vaccine with a ChAdOx1-S booster dose, immunoglobulin G (IgG) anti-spike (anti-S) and anti-nucleocapsid (anti-N) antibody titers (Ab) were compared over 1 year and post-booster vaccination. Results showed that, at 3- to 9-month assessments in vaccinated subjects, an-ti-N Ab were undetectable in participants with no history of COVID-19. In contrast, anti-S Ab measurements were lower than those with COVID-19, and a decrease was observed during the 9 months of observation. After booster vaccination, no differences were found in anti-S between participants who reported a history of COVID-19 and those who did not. Anti-S levels were higher after booster vaccination measurement vs. at 9 months in participants with COVID-19 and without COVID-19, i.e., independent of an infection history. Vaccine administration elicited a response of higher anti-S IgG levels in those infected before vaccination, although levels decreased during the first nine months. IgG anti-N titers were higher in participants with a history of declared infection and who were asymptomatic. The ChAdOx1-S booster increased anti-S Ab levels in participants regardless of whether they had been infected or not to a significantly higher value than with the first two vaccines. These findings underscore the importance of booster vaccination in eliciting a robust and sustained immune response against COVID-19, regardless of the prior infection status.

SARS-CoV-2 specific antibody response after an mRNA vaccine as the third dose: Homologous versus heterologous boost

The aim of this study was to evaluate immunogenicity and longevity of the humoral immune response within six months after the homologous (BNT162b2/BNT162b2) or heterologous (BBIBP-CorV/BNT162b2) third dose, and to assess breakthrough infections among vaccinees during the Omicron wave in Serbia. Serum samples were analyzed at four timepoints: five months after the primary series; three weeks, three months, and six months after the boost. IgG antibodies against the receptor-binding domain of the spike protein were detected using enzyme-linked fluorescence assay. Both homologous (n = 55) and heterologous group (n = 36) showed a highly significant increase in antibody concentrations (p < 0.001) three weeks after the boost. A moderate inverse correlation between the age of recipients and the antibody levels at three weeks post-boost was observed in the homologous group (p = 0.02, r = -0.37), while the same correlation was not significant for heterologous group (p = 0.55, r = -0.15). Heterologous group had significantly higher antibody concentrations than homologous group at three weeks (Median 851.4(IQR 766.6-894.1); 784.3(676.9-847.4); p = 0.03) and three months post-boost (766.6(534.8-798.9); 496.8(361.6-664.0); p < 0.001). However, a significant decline in antibody response over time was noted for both strategies. The overall incidence of breakthrough cases was estimated at 36.36% (20/55) for homologous, and 16.67% (6/36) for heterologous group, but none of them required hospitalization. Although observed incidence in the homologous group was more than double when compared to the heterologous group, this difference was not statistically significant, most likely due to the small sample size. In conclusion, waning immunity after inactivated vaccine can be recovered by BNT162b2 heterologous boost regardless of the age of recipients, and both boost strategies induced potent humoral immune response and protection against severe COVID-19 during the Omicron wave. However, as the observed incidence of breakthrough infections was higher in the homologous group, although non-significant, this finding could indicate an advantage of heterologous approach.

Long-term immunogenicity and safety of heterologous boosting with a SARS-CoV-2 mRNA vaccine (SYS6006) in Chinese participants who had received two or three doses of inactivated vaccine

The emerging new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) needs booster vaccination. We evaluated the long-term safety and immunogenicity of heterologous boosting with a SARS-CoV-2 messenger RNA vaccine SYS6006. A total of 1000 participants aged 18 years or more who had received two (Group A) or three (Group B) doses of SARS-CoV-2 inactivated vaccine were enrolled and vaccinated with one dose of SYS6006 which was designed based on the prototype spike protein and introduced mutation sites. Adverse events (AEs) through 30 days and serious AEs during the study were collected. Live-virus and pseudovirus neutralizing antibody (Nab), binding antibody (immunoglobulin G [IgG]) and cellular immunity were tested through 180 days. Solicited all, injection-site and systemic AEs were reported by 618 (61.8%), 498 (49.8%), and 386 (38.6%) participants, respectively. Most AEs were grade 1. The two groups had similar safety profile. No vaccination-related SAEs were reported. Robust wild-type (WT) live-virus Nab response was elicited with peak geometric mean titers (GMTs) of 3769.5 (Group A) and 5994.7 (Group B) on day 14, corresponding to 1602.5- and 290.8-fold increase versus baseline, respectively. The BA.5 live-virus Nab GMTs were 87.7 (Group A) and 93.2 (Group B) on day 14. All participants seroconverted for WT live-virus Nab. Robust pseudovirus Nab and IgG responses to wild type and BA.5 were also elicited. ELISpot assay showed robust cellular immune response, which was not obviously affected by virus variation. In conclusion, SYS6006 heterologous boosting demonstrated long-term good safety and immunogenicity in participants who had received two or three doses of SARS-CoV-2 inactivated vaccine.

Vaccine Effectiveness against SARS-CoV-2 Infection during the Circulation of Alpha, Delta, or Omicron Variants: A Retrospective Cohort Study in a Tertiary Hospital in Serbia

The COVID-19 pandemic prompted rapid vaccine development and deployment worldwide. Despite widespread vaccination efforts, understanding the effectiveness of vaccines in hospitalized patients remains a critical concern. This retrospective cohort study, conducted at a tertiary healthcare centre in Serbia, tracked patients hospitalized during different waves of COVID-19 variants-Alpha, Delta, and Omicron. Data collection included demographics, comorbidities, symptoms, and vaccination status. Among 3593 patients, those with prior exposure to COVID-19 cases or hospital treatment showed higher positivity rates. Symptom prevalence varied across waves, with coughs persisting. Patients without chronic diseases were more frequent among those testing negative. Vaccine effectiveness varied, with Sinopharm demonstrating a 45.6% effectiveness initially and Pfizer-BioNTech showing an effectiveness of up to 74.8% within 0-84 days after the second dose. Mixed-dose strategies, notably Sinopharm as a primary dose followed by a Pfizer-BioNTech booster, suggested increased protection. Despite substantial vaccination availability, a significant portion of hospitalized patients remained unvaccinated. This study underscores the dynamic nature of vaccine effectiveness and advocates for booster strategies to address evolving challenges in combating COVID-19, particularly in hospitalized patients.

Effect of homologous or heterologous vaccine booster over two initial doses of inactivated COVID-19 vaccine

INTRODUCTION

Inactivated vaccines were delivered to low- and middle-income countries during the early pandemics of COVID-19. Currently, more than 10 inactivated COVID-19 vaccines have been developed. Most inactivated vaccines contain an inactivated whole-cell index SARS-CoV-2 strain that is adjuvant. Whole virions inactivated with aluminum hydroxide vaccines were among the most commonly used. However, with the emerging of COVID-19 variants and waning of the immunity of two doses of after 3 months, WHO and many local governments have recommended the booster-dose program especially with heterologous platform vaccine.

AREA COVERED

This review was conducted through a literature search of the MEDLINE database to identify articles published from 2020 to 2023 covered the inactivated COVID-19 vaccines primary series with homologous and heterologous booster focusing on safety, immunogenicity, efficacy, and effectiveness.

EXPERT OPINION

The inactivated vaccines, especially whole virion inactivated in aluminum hydroxide appeared to be safe and had good priming effects. Immune responses generated after one dose of heterologous boost were high and able to preventing severity of disease and symptomatic infection. A new approach to inactivated vaccine has been developed using inactivating recombinant vector virus-NDV-HXP-S vaccine.

Safety and immunogenicity of primary vaccination with a SARS-CoV-2 mRNA vaccine (SYS6006) in Chinese participants aged 18 years or more: Two randomized, observer-blinded, placebo-controlled and dose-escalation phase 1 clinical trials

Vaccination plays a key role in preventing morbidity and mortality caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We aimed to evaluate the safety and immunogenicity of a SARS-CoV-2 messenger ribonucleic acid (mRNA) vaccine SYS6006. In the two randomized, observer-blinded, placebo-controlled phase 1 trials, 40 adult participants aged 18-59 years and 40 elderly participants aged 60 years or more were randomized to receive two doses of SYS6006 or placebo (saline). Adverse events (AEs) were collected through 30 days post the second vaccination. Immunogenicity was assessed by live-virus neutralizing antibody (Nab), spike protein (S1) binding antibody (S1-IgG), and cellular immunity. The result showed that 7/15, 9/15 and 4/10 adult participants, and 9/15, 8/15 and 4/10 elderly participants reported at least one AE in the 20-µg, 30-µg and placebo groups, respectively. Most AEs were grade 1. Injection-site pain was the most common AE. Two adults and one elder reported fever. No vaccination-related serious AE was reported. SYS6006 elicited wild-type Nab response with a peak geometric mean titer of 232.1 and 130.6 (adults), and 48.7 and 66.7 (elders), in the 20-µg and 30-µg groups, respectively. SYS6006 induced moderate-to-robust Nab response against Delta, and slight Nab response against Omicron BA.2 and BA.5. Robust IgG response against wild type and BA.2 was observed. Cellular immune response was induced. In conclusion, two-dose primary vaccination with SYS6006 demonstrated good safety and immunogenicity during a follow-up period of 51 days in immunologically naive population aged 18 years or more. (Trial registry: Chictr.org.cn ChiCTR2200059103 and ChiCTR2200059104).

Heterologous prime-boost with mRNA-1273 stimulates persistent neutralising antibodies in BBIBP-CorV-vaccinated individuals

BBIBP-CorV inactivated vaccine is one of the most prevalent vaccines globally, but immune responses are far less studied than novel COVID-19 vaccine platforms. Longitudinal studies on BBIBP-CorV with homologous and heterologous booster doses are limited. This study follows a subset of participants from a national study comparing the immunogenicity of COVID-19 vaccines and levels of SARS-CoV-2 neutralising antibody (NAb). Homologous and heterologous booster dose significantly increased NAb levels in BBIBP-CorV-vaccinated individuals. Similar NAb levels were observed 1 month following BNT162b2 or mRNA-1273 booster. Interestingly, NAb persisted following mRNA-1273 booster (n = 95), but waned significantly at 6 and 9 months following BNT162b2 booster (n = 50; P > 0.001). The persistence of NAb was also observed following breakthrough infection. This study provides evidence that not all mRNA vaccines are equal in the longer term and should provide valuable information for policy makers planning booster programmes for BBIBP-CorV vaccinated populations.

Safety and immunogenicity of multivalent SARS-CoV-2 protein vaccines: a randomized phase 3 trial

Background

COVID-19 vaccines that offer broad-spectrum protection are needed. We aimed to evaluate the safety and immunogenicity of multivalent vaccines, SCTV01E and SCTV01C, and compare them with an inactivated vaccine.

Methods

In the phase 3 trial (ClinicalTrials.gov: NCT05323461), adult participants previously vaccinated with Sinopharm's inactivated SARS-CoV-2 vaccine (BBBIP-CorV) were assigned to receive one booster dose of BBBIP-CorV, 20 μg SCTV01C, or 30 μg SCTV01E. The primary endpoint was to evaluate the geometric mean titers (GMT) of neutralizing antibody (nAb) against the Delta and Omicron BA.1 variants on day 28 after injection. Additional endpoints included GMTs of nAb against Delta (B.1.617.2) and Omicron BA.1 variants on day 180, GMTs against BA.5 on day 28, as well as solicited adverse events (AEs) within seven days, unsolicited AEs within 28 days, and serious AEs, AEs of special interest within 180 days after vaccination.

Findings

Between May 30, 2022 and October 28, 2022, a total of 1351 participants were randomized to BBBIP-CorV, SCTV01C, or SCTV01E in a 1:1:1 ratio, with immunogenicity assessments performed on the first 300 participants. For BBBIP-CorV, SCTV01C, and SCTV01E groups, the day 28 GMTs of neutralizing antibody against Omicron BA.1 were a 2.38-, 19.37-, and 28.06-fold increase from baseline; the GMTs against Omicron BA.5 were 2.07-, 15.89- and 21.11-fold increases; the GMTs against Delta variants were 1.97-, 12.76-, and 15.88-fold increases, respectively. The day 28 geometric mean ratio (GMR) of SCTV01C/BBIBP-CorV for Omicron BA.1 was 6.49 (95% CI: 4.75, 8.88), while the GMR of SCTV01E/BBIBP-CorV was 9.56 (95% CI: 6.85, 13.33). For the Delta variant, the day 28 GMR of SCTV01C/BBIBP-CorV was 6.26 (95% CI: 4.78, 8.19), and the day 28 GMR of SCTV01E/BBIBP-CorV was 7.26 (95% CI: 5.51, 9.56). On Day 180, the GMTs against Omicron BA.1 were 2.80-, 9.51-, and 15.56-fold increase from baseline, while those against Delta were 1.58-, 5.49-, and 6.63-fold for BBBIP-CorV, SCTV01C, and SCTV01E groups, respectively. Subgroup analyses showed that SCTV01C and SCTV01E induced uniformly high GMTs against both BA.1 and BA.5, demonstrating its superiority over BBIBP-CorV, regardless of baseline GMT levels. Safety and reactogenicity were similar among the three vaccines. Most AEs were Grade 1 or 2. There were 15 ≥Grade 3 AEs: 6 in the BBIBP-CorV group, 4 in the SCTV01C group and 5 in the SCTV01E group. No SAE was reported and one grade 1 AESI (Bell's palsy) was observed in SCTV01C group.

Interpretation

A booster dose of the tetravalent vaccine SCTV01E consistently induced high neutralizing antibody responses against Omicron BA.1, BA.5, and Delta variants, demonstrating superiority over inactivated vaccine. There is evidence to suggest that SCTV01E may have GMT superiority over bivalent vaccine SCTV01C against Delta, BA.1 and BA.5 variants.

Funding

This study was sponsored by Sinocelltech Ltd., and funded by the Beijing Science and Technology Planning Project [Z221100007922012] and the National Key Research and Development Program of China [2022YFC0870600].

Safety, immunogenicity, and efficacy of an mRNA COVID-19 vaccine (RQ3013) given as the fourth booster following three doses of inactivated vaccines: a double-blinded, randomised, controlled, phase 3b trial

Background

Heterologous vaccine schedules have been recommended to provide superior immunity and protection against emergent SARS-CoV-2 variants of concern. We aimed to evaluate the safety, immunogenicity, and efficacy of an mRNA COVID-19 vaccine RQ3013 compared with adenoviral vectored vaccine Ad5-nCoV and protein subunit vaccine ZF2001 as the fourth dose in adults primed with three doses of inactivated vaccines in China.

Methods

We conducted a double-blinded, randomised, controlled, phase 3b trial among healthy Chinese adults at Lancang County, Yunnan, China. Adults who had received three doses of inactivated COVID-19 vaccines at least 6 months prior were randomly allocated (3:1:1) to receive heterologous boosters with RQ3013, Ad5-nCoV, or ZF2001. We assessed safety within 28 days post boost and the serum geometric mean titres (GMTs) of neutralising antibodies (NAbs) against the live SARS-CoV-2 omicron variant BA.5 on day 14 post-boost. We used Poisson regression to assess the vaccine efficacy against the first episode of virologically confirmed symptomatic COVID-19 occurring at least 7 days post boost. Subgroup analyses categorized by age and sex were also performed for safety and immunogenicity outcomes. This trial has been registered with the Chinese Clinical Trial Registry (ChiCTR2200065281) and is now complete.

Findings

Between December 12 and December 18, 2022, a total of 1382 adults were screened, and 1250 were enrolled and randomly assigned to receive one dose of RQ3013 (n = 750), Ad5-nCoV (n = 250), or ZF2001 (n = 250). Although solicited adverse reactions within 28 days post boost were more frequent in the RQ3013 group (175 [23.3%]) compared to the control groups (24 [9.6%] in both the Ad5-nCOV and ZF2001 groups, P < 0.05), incidences of Grade 3 events were low (9 [0.7%]) and comparable across three groups (P > 0.05). On day 14 post-boost, RQ3013 (GMT 69.14, 95% CI 47.90-99.81) elicited 4.8-fold and 5.6-fold higher concentrations of NAbs against BA.5 than did Ad5-nCoV (14.37, 7.78-26.56) and ZF2001 (12.21, 5.13-29.06), respectively. On day 28 post-boost, RQ3013 demonstrated a relative efficacy of 62.2% (95% CI 13.7-83.1, P = 0.02) compared to Ad5-nCoV, and of 69.0% (33.5-85.7, P = 0.002) compared to ZF2001.

Interpretation

The administrations of all the three heterologous boosters were well tolerated. The heterologous prime-boost regimen with RQ3013 elicited superior immune responses and demonstrated better protection against symptomatic SARS-CoV-2 infections compared with Ad5-nCoV or ZF2001, supporting the use of RQ3013 as a booster vaccination in adults.

Funding

Yunnan Province Science and Technology Department (grant no.202302AA310047).

Humoral response after a BNT162b2 heterologous third dose of COVID-19 vaccine following two doses of BBIBP-CorV among healthcare personnel in Peru

Background

The inactivated virus vaccine, BBIBP-CorV, was principally distributed across low- and middle-income countries as primary vaccination strategy to prevent poor COVID-19 outcomes. Limited information is available regarding its effect on heterologous boosting. We aim to evaluate the immunogenicity and reactogenicity of a third booster dose of BNT162b2 following a double BBIBP-CorV regime.

Methods

We conducted a cross-sectional study among healthcare providers from several healthcare facilities of the Seguro Social de Salud del Perú - ESSALUD. We included participants two-dose BBIBP-CorV vaccinated who presented a three-dose vaccination card at least 21 days passed since the vaccinees received their third dose and were willing to provide written informed consent. Antibodies were determined using LIAISON® SARS-CoV-2 TrimericS IgG (DiaSorin Inc., Stillwater, USA). Factors potentially associated with immunogenicity, and adverse events, were considered. We used a multivariable fractional polynomial modeling approach to estimate the association between anti-SARS-CoV-2 IgG antibodies' geometric mean (GM) ratios and related predictors.

Results

We included 595 subjects receiving a third dose with a median (IQR) age of 46 [37], [54], from which 40% reported previous SARS-CoV-2 infection. The overall geometric mean (IQR) of anti-SARS-CoV-2 IgG antibodies was 8,410 (5,115 - 13,000) BAU/mL. Prior SARS-CoV-2 history and full/part-time in-person working modality were significantly associated with greater GM. Conversely, time from boosting to IgG measure was associated with lower GM levels. We found 81% of reactogenicity in the study population; younger age and being a nurse were associated with a lower incidence of adverse events.

Conclusions

Among healthcare providers, a booster dose of BNT162b2 following a full BBIBP-CorV regime provided high humoral immune protection. Thus, SARS-CoV-2 previous exposure and working in person displayed as determinants that increase anti-SARS-CoV-2 IgG antibodies.

OVX033, a nucleocapsid-based vaccine candidate, provides broad-spectrum protection against SARS-CoV-2 variants in a hamster challenge model

Spike-based COVID-19 vaccines induce potent neutralizing antibodies but their efficacy against SARS-CoV-2 variants decreases. OVX033 is a recombinant protein composed of the full-length nucleocapsid (N) protein of SARS-CoV-2 genetically fused to oligoDOM^®, a self-assembling domain which improves antigen immunogenicity. OVX033 including N as an antigenic target is proposed as new vaccine candidate providing broad-spectrum protection against sarbecoviruses. OVX033 demonstrated its ability to trigger cross-reactive T cell responses and cross-protection against three variants of SARS-CoV-2 (B.1 Europe, Delta B.1.617.2, and Omicron B.1.1.529) in a hamster challenge model, as evidenced by lower weight loss, lower lung viral loads, and reduced lung histopathological lesions.