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The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants and the waning of vaccine-elicited neutralizing antibodies suggests that additional coronavirus disease 2019 (COVID-19) vaccine doses may be needed for individuals who initially received CoronaVac. We evaluated the safety and immunogenicity of the recombinant adenovirus type 5 (AD5)-vectored COVID-19 vaccine Convidecia as a heterologous booster versus those of CoronaVac as homologous booster in adults previously vaccinated with CoronaVac in an ongoing, randomized, observer-blinded, parallel-controlled phase 4 trial ( NCT04892459 ). Adults who had received two doses of CoronaVac in the past 3–6 months were vaccinated with Convidecia ( n  = 96) or CoronaVac ( n  = 102). Adults who had received one dose of CoronaVac in the past 1–3 months were also vaccinated with Convidecia ( n  = 51) or CoronaVac ( n  = 50). The co-primary endpoints were the occurrence of adverse reactions within 28 d after vaccination and geometric mean titers (GMTs) of neutralizing antibodies against live wild-type SARS-CoV-2 virus at 14 d after booster vaccination. Adverse reactions after vaccination were significantly more frequent in Convidecia recipients but were generally mild to moderate in all treatment groups. Heterologous boosting with Convidecia elicited significantly increased GMTs of neutralizing antibody against SARS-CoV-2 than homologous boosting with CoronaVac in participants who had previously received one or two doses of CoronaVac. These data suggest that heterologous boosting with Convidecia following initial vaccination with CoronaVac is safe and more immunogenic than homologous boosting. Heterologous vaccination with Convidecia, a recombinant adenovirus type 5-vectored COVID-19 vaccine, after one or two doses of CoronaVac, an inactivated SARS-CoV-2 vaccine, is more reactogenic but elicits significantly higher levels of neutralizing antibodies than homologous vaccination.

An effective vaccine is needed to end the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Here, we assess the preliminary safety, tolerability and immunogenicity data from an ongoing single-center (in Jiangsu province, China), parallel-group, double-blind phase 1 trial of the vaccine candidate BNT162b1 in 144 healthy SARS-CoV-2-naive Chinese participants. These participants are randomized 1:1:1 to receive prime and boost vaccinations of 10 µg or 30 µg BNT162b1 or placebo, given 21 d apart, with equal allocation of younger (aged 18–55 years) and older adults (aged 65–85 years) to each treatment group (ChiCTR2000034825). BNT162b1 encodes the SARS-CoV-2 spike glycoprotein receptor-binding domain (RBD) and is one of several messenger RNA-based vaccine candidates under clinical investigation. Local reactions and systemic events were generally dose dependent, transient and mild to moderate. Fever was the only grade 3 adverse event. BNT162b1 induced robust interferon-γ T cell responses to a peptide pool including the RBD in both younger and older Chinese adults, and geometric mean neutralizing titers reached 2.1-fold (for younger participants) and 1.3-fold (for the older participants) that of a panel of COVID-19 convalescent human sera obtained at least 14 d after positive SARS-CoV-2 polymerase chain reaction test. In summary, BNT162b1 has an acceptable safety profile and produces high levels of humoral and T cell responses in an Asian population. Phase 1 trial results of the messenger RNA vaccine candidate BNT162b1, which encodes the receptor-binding domain of the SARS-CoV-2 spike protein, show safety and elicitation of antibody and T cell responses in both younger and older Chinese adults.

In response to the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic, over 200 vaccine candidates against coronavirus disease 2019 (COVID-2019) are under development and currently moving forward at an unparalleled speed. The availability of surrogate endpoints would help to avoid large-scale filed efficacy trials and facilitate the approval of vaccine candidates, which is crucial to control COVID-19 pandemic. Several phase 3 efficacy trials of COVID-19 vaccine candidates are under way, which provide opportunities for the determination of COVID-19 correlates of protection. In this paper, we review current knowledge for existence of COVID-19 correlates of protection, methods for assessment of immune correlates of protection and issues related to COVID-19 correlates of protection.

Heterologous boost vaccination has been proposed as an option to elicit stronger and broader, or longer-lasting immunity. We assessed the safety and immunogenicity of heterologous immunization with a recombinant adenovirus type-5-vectored Coronavirus Disease 2019 (COVID-19) vaccine (Convidecia, hereafter referred to as CV) and a protein-subunit-based COVID-19 vaccine (ZF2001, hereafter referred to as ZF). We conducted a randomized, observer-blinded, placebo-controlled trial, in which healthy adults aged 18 years or older, who have received 1 dose of Convidecia, with no history of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, were recruited in Jiangsu, China. Sixty participants were randomly assigned (2:1) to receive either 1 dose of ZF2001 or placebo control (trivalent inactivated influenza vaccine (TIV)) administered at 28 days after priming, and received the third injection with ZF2001 at 5 months, referred to as CV/ZF/ZF (D0-D28-M5) and CV/ZF (D0-M5) regimen, respectively. Sixty participants were randomly assigned (2:1) to receive either 1 dose of ZF2001 or TIV administered at 56 days after priming, and received the third injection with ZF2001 at 6 months, referred to as CV/ZF/ZF (D0-D56-M6) and CV/ZF (D0-M6) regimen, respectively. Participants and investigators were masked to the vaccine received but not to the boosting interval. Primary endpoints were the geometric mean titer (GMT) of neutralizing antibodies against wild-type SARS-CoV-2 and 7-day solicited adverse reactions. The primary analysis was done in the intention-to-treat population. Between April 7, 2021 and May 6, 2021, 120 eligible participants were randomly assigned to receive ZF2001/ZF2001 (n = 40) or TIV/ZF2001 (n = 20) 28 days and 5 months post priming, and receive ZF2001/ZF2001 (n = 40) or TIV/ZF2001 (n = 20) 56 days and 6 months post priming. Of them, 7 participants did not receive the third injection with ZF2001. A total of 26 participants (21.7%) reported solicited adverse reactions within 7 days post boost vaccinations, and all the reported adverse reactions were mild, with 13 (32.5%) in CV/ZF/ZF (D0-D28-M5) regimen, 7 (35.0%) in CV/ZF (D0- M5) regimen, 4 (10.0%) in CV/ZF/ZF (D0-D56-M6) regimen, and 2 (10.0%) in CV/ZF (D0-M6) regimen, respectively. At 14 days post first boost, GMTs of neutralizing antibodies in recipients receiving ZF2001 at 28 days and 56 days post priming were 18.7 (95% CI 13.7 to 25.5) and 25.9 (17.0 to 39.3), respectively, with geometric mean ratios of 2.0 (1.2 to 3.5) and 3.4 (1.8 to 6.4) compared to TIV. GMTs at 14 days after second boost of neutralizing antibodies increased to 107.2 (73.7 to 155.8) in CV/ZF/ZF (D0-D28-M5) regimen and 141.2 (83.4 to 238.8) in CV/ZF/ZF (D0-D56-M6) regimen. Two-dose schedules of CV/ZF (D0-M5) and CV/ZF (D0-M6) induced antibody levels comparable with that elicited by 3-dose schedules, with GMTs of 90.5 (45.6, 179.8) and 94.1 (44.0, 200.9), respectively. Study limitations include the absence of vaccine effectiveness in a real-world setting and current lack of immune persistence data. Heterologous boosting with ZF2001 following primary vaccination with Convidecia is more immunogenic than a single dose of Convidecia and is not associated with safety concerns. These results support flexibility in cooperating viral vectored and recombinant protein vaccines. Study on Heterologous Prime-boost of Recombinant COVID-19 Vaccine (Ad5 Vector) and RBD-based Protein Subunit Vaccine; ClinicalTrial.gov NCT04833101.

Determining the duration of immunity induced by booster doses of CoronaVac is crucial for informing recommendations for booster regimens and adjusting immunization strategies. In two single-centre, double-blind, randomised, placebo-controlled phase 2 clinical trials, immunogenicity and safety of four immunization regimens are assessed in adults aged 18 to 59 years and one immunization regimen in adults aged 60 years and older, respectively. Serious adverse events occurring within 6 months after booster doses are recorded as pre-specified secondary endpoints, geometric mean titres (GMTs) of neutralising antibodies one year after the 3-dose schedule immunization and 6 months after the booster doses are assessed as pre-specified exploratory endpoints, GMT fold-decreases in neutralization titres are assessed as post-hoc analyses. Neutralising antibody titres decline approximately 4-fold and 2.5-fold from day 28 to day 180 after third doses in adults aged 18–59 years of age and in adults aged 60 years and older, respectively. No safety concerns are identified during the follow-up period. There are increases in the magnitude and duration of humoral response with homologous booster doses of CoronaVac given 8 months after a primary two-dose immunization series, which could prolong protection and contribute to building our wall of population immunity. Trial number: NCT04352608 and NCT04383574. Following a booster dose of CoronaVac in two single-centre phase 2 clinical trials, the authors show that neutralising antibody titres decline approximately 4-fold and 2.5-fold from day 28 to day 180 in adults aged 18-59 years and in adults aged 60 years and older, respectively.

We conducted a multicenter, partially randomized, platform trial to assess the effectiveness of a booster dose of an aerosolized or intramuscular adenovirus type 5 vectored COVID-19 vaccine (Ad5-nCoV) in Chinese adults (NCT05855408). Between May 23, 2023, and August 28, 2023, 4089 eligible participants were equally randomized to receive either a booster dose of aerosolized Ad5-nCoV via oral inhalation at 0.1 mL (IH Ad5-nCoV, n = 2039) or an intramuscular injection of Ad5-nCoV at 0.5 mL (IM Ad5-nCoV, n = 2050). Additionally, 2008 participants who declined the booster but consented to participate in COVID-19 surveillance were enrolled in the control group. All participants were monitored for symptomatic COVID-19 over a six-month surveillance period for the primary outcome. From 14 days after the vaccination, 14 (15/1000 person-years), 19 (20/1000 person-years), and 34 (37/1000 person-years) COVID-19 cases were confirmed in the IH Ad5-nCoV group, the IM Ad5-nCoV group, and the control group, respectively, which resulted in an adjusted effectiveness of 52.3% (95% CI 10.4 to 74.6) for IH Ad5-nCoV and 37.2% (95% CI -11.2 to 64.5) for IM Ad5-nCoV. The IH Ad5-nCoV booster was associated with a lower incidence of symptomatic COVID-19, but there is no solid evidence that IH Ad5-nCoV was more effective than IM Ad5-nCoV. In this partially randomized clinical trial, the authors find that an orally inhaled Ad5-nCoV booster is associated with a lower incidence of symptomatic COVID-19 during the following 6 months compared with controls who haven’t received a booster. Intramuscular administered Ad5-CoV booster is associated with reduced COVID-19 incidence as well.

Objectives: To determine whether a Sabin strain inactivated poliovirus booster (sIPV) given concomitantly (same day, different sites) with MMRV or inactivated hepatitis A vaccine (HepA) is non-inferior in immunogenicity and comparable in safety to separate administration at the 18-month visit. Methods: Open-label, randomized Phase IV trial in healthy children (18~22 months), allocated 2:2:2:1:1 to sIPV&MMRV, sIPV&HepA, sIPV-only, MMRV-only, or HepA-only. Primary endpoints were Day-30 seroconversion rates (SCRs) for poliovirus types 1–3 (sIPV arms) and for HepA (HepA arms). Results: Of 892 screened, 889 were randomized; baseline characteristics were balanced. By Day 30, seroprotection was 100% for PV types 1–3 in all sIPV-containing arms. SCRs were high and similar across concomitant vs. separate administration; all pairwise SCR differences met non-inferiority (−10% margin). Adjusted post-vaccination GMTs were comparable across serotypes. For HepA, Day-30 SPoR was 99.3% vs. 100.0%, and adjusted GMC was 412.2 vs. 465.9 (p = 0.2224). For MMRV, Day-30 SPoR was 100% in both groups with similar adjusted GMCs. Within 30 days, overall adverse reactions were 14.5%/17.4%/16.3%/7.3%/10.8% (sIPV&MMRV/sIPV&HepA/sIPV-only/MMRV-only/HepA-only), mostly mild to moderate; no vaccine-related SAEs (NCT06442449). Conclusions: Same-day sIPV co-administration with MMRV or HepA was non-inferior and well tolerated, supporting programmatic adoption.

Background: The previous study assessed the immune durability of the Sabin strain inactivated poliovirus vaccine (sIPV) at four years of age; an update on its long-term persistence is warranted. Methods: This Phase IV, open-label, parallel-controlled observational study, required by China’s National Medical Products Administration (NMPA), involves 6.5-year-old children who received four doses of sIPV or Salk IPV (wIPV) at 2, 3, 4, and 18 months during the Phase III trial. Participants are recruited in a 2:1 ratio and contribute blood samples for polio-neutralizing antibody (nAb) assays to determine non-inferiority of immune persistence. Results: The study enrolled 483 participants aged 6.5 years in the 5-year Immune Persistence Set (IPS2), with 318 in the sIPV group and 165 in the wIPV group. Additionally, 387 participants (255 sIPV, 132 wIPV) with samples at six-time points were included in the Full Sequence Immune Persistence Set (IPS3). In IPS2, seropositivity rates (SPRs) for nAbs against serotypes 1–3 were over 99% in sIPV and 98% in wIPV. At 6.5 years, geometric mean titers (GMTs) were significantly higher in the sIPV group 543.96, 179.59 and 362.72 compared to the wIPV group 190.75, 81.05 and 203.95 for serotypes 1, 2 and 3, respectively. Participants in IPS3 demonstrated comparable SPRs and GMTs to IPS2, with values of 566.01 vs. 187.41 for serotype I, 177.55 vs. 78.01 for serotype II, and 365.47 vs. 190.31 for serotype III in the sIPV and wIPV groups, respectively. From one-month post-booster to 6.5 years, nAb GMTs showed declines: 19.35-fold for serotype I, 28.12-fold for serotype II, and 32.45-fold for serotype III in the sIPV group, and 23.42-fold, 23.83-fold, and 34.54-fold in the wIPV group, respectively. Non-inferiority of nAb SPRs and GMTs for sIPV compared to wIPV among participants aged 6.5 years was confirmed for all serotypes in IPS2 and IPS3. Conclusions: The sIPV maintains good immunological persistence five years after four doses of vaccination, with nAb GMT exceeding the seroprotecting threshold, suggesting that booster doses might be currently unwarranted.

Vaccination with prophylactic human papillomavirus (HPV) vaccines is one of the most effective measures to prevent cervical cancer and other related diseases. Here we aimed to evaluate the immunogenicity and safety of an -produced 9-valent human papillomavirus (9vHPV) vaccine. We did a single-center, randomized, observer-blinded, positive controlled phase 2 clinical trial in healthy women aged 20-45 years. All eligible participants were randomly assigned (1:1:1) to receive 270 ug 9vHPV, 360 ug 9vHPV, or the control vaccine (Gardasil) with a 0-2-6-month schedule. Serum samples were collected at day 0 and month 7 to assess IgG and neutralizing antibodies (nAbs). For HPV 6/HPV 11/HPV 16/HPV 18, non-inferiority was identified for the lower limit of the 95% CI of the geometric mean titer (GMT) ratio at a margin of 0.5 and a seroconversion rate (SCR) difference at a margin of -5%. For HPV 31/HPV 33/HPV 45/HPV 52/HPV 58, superiority was demonstrated if the lower limit of the 95% CI for GMT ratio is greater than 1. A total of 780 participants aged 20-45 years were enrolled, among whom 770 completed the three-dose immunization schedule. The incidences of ARs within 7 days in the 270 μg, 360 μg, and positive control groups were 38.85%, 41.92%, and 22.69%, respectively ( < 0.001). The GMTs of nAbs and IgG antibodies for nine HPV types in both 270 ug and 360 ug groups showed an obvious rise at month 7. For HPV 31/HPV 33/HPV 45/HPV 52/HPV 58, the GMTs of nAbs in both 270 μg and 360 μg groups were higher than those in the positive control group, with the 95% CI lower bounds of GMT ratios all greater than 1. Compared to the positive control group, HPV 6 and HPV 18 achieved non-inferiority criteria for GMT in both dose groups. However, the GMT ratio of HPV 16 in the 270 μg group was 0.46 (0.38-0.55), and HPV 16 and HPV 11 in the 360 μg group were 0.48 (0.40-0.58) and 0.53 (0.46-0.60), respectively. The SCRs of nAbs for HPV 6/HPV 11/HPV 16/HPV 18 in the three groups were 100%, with the 95% CI lower bound for SCR differences ranging from -2.55% to -1.64%. The candidate 9vHPV vaccine was well tolerated and immunogenic, supporting further evaluation for efficacy and safety in larger populations. https://clinicaltrials.gov, identifier NCT05694728.

Background A two-dose primary regimen of INO-4800 DNA vaccine demonstrated only modest immunogenicity in the previous phase 2 clinical trial. This booster study aimed to evaluate the immunogenicity and safety of a booster dose of INO-4800 in adults previously received two-dose regimen of INO-4800. Methods Healthy adults who received two doses of INO-4800 (1.0 mg or 2.0 mg) at least 12 months ago in a previous phase 2 trial were eligible for this booster study, conducted in Danyang, Jiangsu Province, China. Eligible participants were stratified by primary vaccination dose (1.0 mg or 2.0 mg) and age group (18–59 years or ≥ 60 years), and subsequently randomized in a 1:1 ratio to receive a third dose of INO-4800 or placebo at the same dosage as previously administered. The primary immunogenicity endpoint was the geometric mean concentrations (GMCs) of spike-binding antibodies on day 14 post-booster. The primary safety endpoint was the occurrence of adverse reactions within 14 days. Results Between December 20 and 23, 2021, 200 eligible participants were enrolled. 100 eligible participants who received two doses of 2.0 mg INO-4800 were randomly assigned (1:1) to receive a third dose of 2.0 mg INO-4800 ( n  = 50) or 2.0 mg placebo ( n  = 50). Another 100 eligible participants who received two doses of 1.0 mg INO-4800 were randomly assigned (1:1) to receive a third dose of 1.0 mg INO-4800 ( n  = 50) or 1.0 mg placebo ( n  = 50). On day 14 post-booster, the GMCs of spike-binding antibodies were significantly higher in 2.0 mg INO-4800 group ( 260.1 BAU/mL) compared to placebo group (2.8 BAU/mL, p  < 0.001), and in 1.0 mg INO-4800 group (104.2 BAU/mL) compared to placebo group (2.5 BAU/mL, p  < 0.001). The most common local reactions were injection site redness, occurring at rate of 16.0% in the INO-4800 groups.All adverse reactions were mild to moderate in severity and occurred within 14 days post-booster. No vaccine related serious adverse events were reported. Conclusions The booster regimen of one dose INO-4800 is safe and modestly immunogenic in individuals who previously received a two- dose regimen of INO-4800, with the 2.0 mg INO-4800 demonstrating superior immunogenicity compared to the 1.0 mg INO-4800. Trial registration www.chictr.org.cn , identifier is ChiCTR2100054324.(December 13 2021).