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

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.

Interchangeability of different COVID-19 vaccine platforms as booster doses: A phase 3 study mimicking real-world practice

BACKGROUND

The COVID-19 pandemic is over but the highly immunized or naturally exposed global population still requires booster vaccinations against newly emerging SARS-CoV-2 variants. We assessed safety and immunogenicity of booster doses of COVID-19 vaccines based on three different platforms in a setting that mimics the current routine practice in Brazil.

METHODS

In this phase 3 study from 14 February 2023 to 12 June 2023 we enrolled previously immunized adults to receive an additional booster dose of one of three vaccines. Immunogenicity against ancestor SARS-CoV-2 and Omicron BF.7, BQ.1.1.3, and XBB.1.5.6 sub-lineages was measured as ELISA IgG or virus neutralizing (VNT) antibodies and safety/reactogenicity assessed using diary cards.

RESULTS

Volunteers with a history of full primary COVID-19 immunization striated to three cohorts according to their previous booster vaccination history-0 (n = 26), 1 (n = 140) or 2 (n = 606) booster vaccinations-were randomized 2:1:1 to receive either recombinant protein (SCB-2019, Clover), adenovirus-vector (ChAdOx1-S, AstraZeneca/Fiocruz), or mRNA (BNT162b2, Pfizer/Wyeth). Baseline antibody titers were higher in individuals who had received one or two boosters and titers against both ancestor and Omicron sub-lineages increased in all groups regardless of the number of previous booster doses or the vaccine used. Day 28 geometric mean titers (GMTs) and geometric mean-fold rises (GMFR) against all variants were higher after BNT162b than SCB-2019 or ChAdOx1-S, but BNT162b groups displayed more rapid antibody waning at Day 84. Within cohorts each vaccine elicited similar GMFR against the different SARS-CoV-2 strains. All vaccines were well tolerated with similar solicited reactogenicity profiles.

CONCLUSIONS

Protein, adenovirus-vector or mRNA vaccine boosters were equally well tolerated and immunogenic against ancestor SARS-CoV-2 and Omicron sub-lineages in fully primed adults with 0-2 prior boosters. BNT162b induced the highest immune responses but also the most rapid waning of antibodies 3 months after vaccination.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier NCT05812586.

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.

Immunogenicity and safety of SARS-CoV-2 recombinant protein subunit vaccine (IndoVac) adjuvanted with alum and CpG 1018 in Indonesian adults: A phase 3, randomized, active-controlled, multicenter trial

BACKGROUND

Bio Farma has developed a recombinant protein subunit vaccine (IndoVac) that is indicated for active immunization in population of all ages. This article reported the results of the phase 3 immunogenicity and safety study in Indonesian adults aged 18 years and above.

METHODS

We conducted a randomized, active-controlled, multicenter, prospective intervention study to evaluate the immunogenicity and safety of IndoVac in adults aged 18 years and above. Participants who were SARS-CoV-2 vaccine-naïve received two doses of either IndoVac or control (Covovax) with 28 days interval between doses and were followed up until 12 months after complete vaccination.

RESULTS

A total of 4050 participants were enrolled from June to August 2022 and received at least one dose of vaccine. The geometric mean ratio (GMR) of neutralizing antibody at 14 days after the second dose was 1.01 (95 % confidence interval (CI) 0.89-1.16), which met the WHO non-inferiority criteria for immunobridging (95 % CI lower bound > 0.67). The antibody levels were maintained through 12 months after the second dose. The incidence rate of adverse events (AEs) were 27.95 % in IndoVac group and 32.15 % in Covovax group with mostly mild intensity (27.70 %). The most reported solicited AEs were pain (14.69 %) followed by myalgia (7.48 %) and fatigue (6.77 %). Unsolicited AEs varied, with each of the incidence rate under 5 %. There were no serious AEs assessed as possibly, probably, or likely related to vaccine.

CONCLUSIONS

IndoVac in adults showed favourable safety profile and elicited non-inferior immune response to Covovax. (ClinicalTrials.gov: NCT05433285, Indonesian Clinical Research Registry: INA-R5752S9).

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.

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.