key: cord-0430673-tvi9a77t
authors: Li, J.; Hou, L.; Guo, X.; Jin, P.; Wu, S.; Zhu, J.; Pan, H.; Wang, X.; Song, Z.; Wan, J.; Cui, L.; Jin, L.; Liu, J.; Shi, F.; Xu, X.; Chen, Y.; Zhu, T.; Chen, W.; Zhu, F.
title: Heterologous prime-boost immunization with CoronaVac and Convidecia
date: 2021-09-06
journal: nan
DOI: 10.1101/2021.09.03.21263062
sha: 8d5d8fcc166fd6d2fe07305b376d6b179a0bd4c8
doc_id: 430673
cord_uid: tvi9a77t

Background The safety and immunogenicity of heterologous prime-boost COVID-19 vaccine regimens with one shot of a recombinant adenovirus type-5-vectored COVID-19 vaccine Convidecia has not been reported. Methods We conducted a randomized, controlled, observer-blinded trial of heterologous prime-boost immunization with CoronaVac and Convidecia in healthy adults 18-59 years of age. Eligible participants who were primed with one or two doses of CoronaVac were randomly assigned at a 1:1 ratio to receive a booster dose of Convidecia or CoronaVac. Participants were masked to the vaccine received but not to the three-dose or two-dose regimen. The occurrences of adverse reactions within 28 days after the vaccination were documented. The geometric mean titers of neutralizing antibodies against live SARS-CoV-2 virus were measured at 14 and 28 days after the booster vaccination. Results Between May 25 and 26, 2021, a total of 300 participants were enrolled. Participants who received a booster shot with a heterologous dose of Convidecia reported increased frequencies of solicited injection-site reactions than did those received a homogeneous dose of CoronaVac, but frequencies of systemic reactions. The adverse reactions were generally mild to moderate. The heterologous immunization with Convidecia induced higher live viral neutralizing antibodies than did the homogeneous immunization with CoronaVac (197.4[167.7, 232.4] vs. 33.6[28.3, 39.8] and 54.4[37. 9, 78.0] vs. 12.8[9.3, 17.5]) at day 14 in the three- and two-dose regimen cohort, respectively. Conclusions The heterologous prime-boost regimen with Convidecia after the priming with CoronaVac was safe and significantly immunogenic than a homogeneous boost with CoronaVac (ClinicalTrials.gov, number NCT04892459).

The heterologous prime-boost regimen with Convidecia after the priming with CoronaVac was safe and significantly immunogenic than a homogeneous boost with CoronaVac (ClinicalTrials.gov, number NCT04892459).

All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 6, 2021. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 6, 2021. vaccine Convidecia (CanSino). According to the results from phase 3 trials, CoronaVac showed a 50.4% of vaccine efficacy against COVID-19 diseases in Brazil, 7 and one shot of Convidecia had about 65% of efficacy in preventing symptomatic diseases. 8 Both of the vaccines were found to be immunogenic and effective, but there is a concern about the waning of vaccine-elicited neutralizing antibodies might make the vaccine inadequately protective in a longer period. Besides, the SARS-CoV-2 variants, with an increased infectivity and transmissibility, may partially escape from vaccine-elicited neutralizing antibodies, and lead to a further decrease of vaccine protection against COVID-19 diseases.

Although, the justification and necessity of a booster vaccination of COVID-19 vaccine is still disputed, clinical trials with heterologous or homogeneous additional dose after the priming series are performed. Heterologous schedules incorporating COVID-19 vaccines across different platforms showed a superior immunogenicity to heterologous schedules in animal studies. 9 Theoretically, heterologous schedules may promote the maturation of antibody affinity and influence the breadth of immunization by inserting different antigens, types of vectors, delivery routes, doses, or adjuvants at different times. 10 There are dozens of various ongoing heterologous All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 6, 2021. ; https://doi.org/10.1101/2021.09.03.21263062 doi: medRxiv preprint booster studies after the primary series, but most of them focused on the ChAdOx1 nCoV-19, BNT162b2 and mRNA-1273. 11 None was heterologous boost study after priming with inactivated COVID-19 vaccines.

Up to now, in mainland China, more than 2.0 billion doses of COVID-19 vaccines have been administered in population, and over 50% of which were inactivated vaccine CoronaVac. 12 Besides, CoronaVac has been authorized to use in 39 countries or areas and been deployed globally, including Brazil, Malaysia, Mexico, Pakistan, Chile, Egypt, Indonesia, Nepal, Turkey. While, Convidecia has been authorized in eight countries or areas. 13 Here, we reported the safety and immunogenicity of the first heterologous prime-boost immunization with an inactivated SARS-CoV-2 vaccine (CoronaVac) and a recombinant adenovirus type-5-vectored COVID-19 vaccine (Convidecia) in Chinese adults at 18 to 59 years of age.

We conducted a randomized, controlled, observer-blinded trial to access the safety and immunogenicity of heterologous prime-boost immunization with CoronaVac and Convidecia. Healthy participants, male or female, aged between 18 and 59 years, who have received one dose of CoronaVac in the past 1~3 months or two doses of CoronaVac in the past 3~6 months were recruited for screening of eligibility.

Participants with a previous clinical or virologic COVID-19 diagnosis or All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in This was a proof of concept trial, initiated by investigators from Jiangsu Provincial Center of Disease Control and Prevention. The trial protocol was reviewed and approved by the institutional review board of the Jiangsu Provincial Center of Disease Control and Prevention, and no protocol change was made after the initial of the study.

This trial was conducted following the principles of the Declaration of Helsinki and local guidelines.

We recruited participants form one clinic site in Lianshui County, Jiangsu Province.

Eligible participants who competed the prime vaccination of two doses of CoronaVac in the past 3~6 months were randomly assigned at a 1:1 ratio to receive a booster dose of Convidecia (group A, heterologous boost dose) or CoronaVac (group B, homogeneous boost dose). While, participants who were primed with one dose of CoronaVac in the past 1~2 months were randomized in a 1:1 ratio to receive a second dose of Convidecia (group C, heterologous dose) or CoronaVac (group D, homogeneous dose). The vaccination records were verified by investigators through the electronic registration system for COVID-19 vaccine immunization. An interactive Web-based response system was used for randomization, and the All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 6, 2021. ; https://doi.org/10.1101/2021.09.03.21263062 doi: medRxiv preprint randomization lists were generated by an independent statistician using SAS (version 9.4).

We masked participants, investigators, laboratory staff, and outcome assessors to the allocation of treatment groups, but not to the three-dose or two-dose regimen.

Designated unblinded personnel were responsible for the preparation and administration of the vaccination, and were forbidden to reveal the identity of the study vaccines to the participants or other investigators. All the vaccinations were administered intramuscularly.

The primary endpoint for safety objective was the occurrence of adverse reactions within 28 days after the vaccination. Participants were observed at the clinic for 30 minutes after the vaccination for any immediate vaccine-associated reactions, and then were instructed to keep a daily record of any solicited or unsolicited adverse events for the next 14 days. Solicited injection-site events included pain, redness, swelling, induration, itch and cellulitis, while systemic events included fever, malaise, muscle ache, joint pain, fatigue, nausea, headache and so on. Unsolicited adverse events within 28 days reported by the participants were also collected. Severity of adverse events are graded according to the standard guidelines issued by the China State Food and Drug Administration, and the causality with immunization before unmasking. Serious adverse events self-reported by participants were documented throughout the study. All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 6, 2021. Receptor binding domain (RBD)-and N-specific ELISA antibody responses were measured at the same time points, using an indirect ELISA assay. RBD-binding IgG isotype in serum was also determined by ELISA, and the type 1 helper T cells (Th1)-dependent IgG1 vs. type 2 helper T cells (Th2)-dependent IgG4 antibody subclasses were calculated to evaluate the Th1/Th2 profiling. The WHO international standard for anti-SARS-CoV-2 immunoglobulin (NIBSC code 20/136) was used side by side as reference with the serum samples measured in this study for calibration and harmonization of the serological assays. 14 The conversion factors to international standard units were showed in the appendix 1. Fold increase of antibody responses All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 6, 2021. 

The sample size calculation was based on the hypothesis on a boost vaccination following the two-dose of inactivated vaccine regimen, and performed by using Power Analysis and Sample Size (PASS) software. We assumed that the GMT of neutralizing antibodies was about 1:40 at baseline before receiving the booster immunization (i.e. three to six months after receiving two doses of inactivated vaccines). After the boost vaccination, the GMTs were expected to reach 1:80 for those receiving a homogeneous dose of CoronaVac, and 1:160 for those receiving a or a heterogeneous of Convidecia at days 14. Equal standard deviation of GMTs of 4 was estimated for both groups. A sample size of 100 per treatment group would provide at least 90% power to detect a difference in log-transformed postvaccination GMTs at the one-sided 2.5% significance level. In this study, a heterogeneous vaccination following one dose of inactivated vaccine were also explored with 50 All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 6, 2021. ; https://doi.org/10.1101/2021.09.03.21263062 doi: medRxiv preprint persons per group, for which the power was not calculated.

We assessed the number and proportion of participants with adverse reactions post vaccination. The antibodies against SARS-CoV-2 were presented as GMTs, geometric mean fold increases (GMFIs) and the proportion of participants with at least four-fold increase with 95% CIs. The cellular responses were shown as the average number of positive cells per million peripheral blood mononuclear cells (PBMCs). We used the χ² test or Fisher's exact test to analyze categorical data, T test to analyze the log transformed antibody titers, and Wilcoxon rank-sum test for non-normal distributed data. The correlation between concentrations of log-transformed neutralizing antibodies and binding antibody was analyzed using Pearson's correlation.

The primary analysis was performed based on the intervention modified intention-to-treat cohort. Statistical analyses were done by using SAS (version 9.4) or GraphPad Prism 8.0.1. This study is registered with ClinicalTrials.gov, number NCT04892459.

Between May 25 and 26, 2021, we recruited 302 participants for screening. A total of 300 participants were enrolled, of whom 200 primed with two doses of inactivated vaccine CoronaVac, and 100 primed with one dose of CoronaVac were randomized (figure 1). One participant only received one prime dose, but was wrongly classified into the cohort having two doses primed, and then randomized to receive a All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 6, 2021. ; https://doi.org/10.1101/2021.09.03.21263062 doi: medRxiv preprint heterologous boost dose of Convidecia. We reclassified this participant into group C.

Two participants who were randomized to group A but were wrongly administrated with a homogeneous boost dose of CoronaVac, were classified into group B. 299 of these participants received a booster dose on day 0, and completed seven days follow-up to assess safety. We obtained serum samples from 298 participants at day 14, and 293 participants at day 28. The demographic characteristics of participants are shown in table 1. Approximately 11.8~27.1% of the participants who completed two doses in the last 3 to 6 months and 4.0~5.9% of those who received one dose in the last 1 to 2 months, showed positive neutralizing antibody against SARS-CoV-2 in serum at the enrollment before receiving a boost vaccination.

In both two-dose and three-dose regimen cohorts, Convidecia recipients reported more adverse reactions than CoronaVac recipients with p values of <0.001 and 0.019, respectively ( Table 2) . Participants in the two-dose regimen cohort, who received the second dose with a heterologous dose of Convidecia reported significant higher occurrence of solicited injection-site reactions than did those received a homogeneous dose of CoronaVac. While, the systemic reactions were reported at similar frequencies between the two groups. In the three-dose regimen cohort, participants received the third dose with a Convidecia following a heterologous prime-boost immunization had significant more solicited injection-site and systemic reactions than those received a homogeneous dose of CoronaVac (29.2% vs. 2.9%, p<0.001, and 13.5% vs. 2.9%, All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in 

isotype showed that the predominant binding antibody responses were associated with IgG1 after the boost in both heterologous or homogeneous vaccine groups (appendix 3). Very mild responses from IgG3 were found in participants receiving heterologous Convidecia, but not in those receiving homogeneous CoronaVac. Nearly no responses of IgG2 and IgG4 were observed across the treatment groups. At day 14, the mean All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 6, 2021. ; https://doi.org/10.1101/2021.09.03.21263062 doi: medRxiv preprint ( figure 3C, D, E) . Overall, we observed a robust Th1 biased cellular immune response, but low levels of Th2-biased cytokines IL-4, IL-5, and IL-13 in the heterologous vaccination groups, resulting in higher Th1/Th2 cytokine ratios than those in the homogeneous groups ( figure 3F ).

Our results suggest that the heterologous prime-boost regimens with one dose of perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The concerns about the duration of protection against SARS-CoV-2 induced by the licensed two-dose regimen of inactivated COVID-19 vaccines were raised in both the clinical trials and post-licensure studies, which showed that the humoral immunity waned significantly over time, and protection might be lost, particularly when the variants are dominant. [15] [16] [17] [18] In our study, participants were enrolled within 1-2 months after receiving one dose of inactivated COVID-19 vaccine, or within 3-6 months after completing two doses of inactivated COVID-19 vaccine. We found that the pre-boost antibody titer level of these participants at enrollment were very low, which was in line with that previously reported. 19 Recently, a study on a booster dose of CoronaVac vaccine in adults aged 18-59 years at 6-month interval induced approximately 3-fold increase of the neutralizing antibody titers above the peak responses induced by two-dose regimen of CoronaVac. 19 Although homologous prime-boost immunization has typically been effective for the diseases of the Expanded Program of Immunizations, but in our study, heterologous prime-boost are more immunogenic.

This may be related to the different natural immune responses activated by the inactivated vaccine and the viral-vectored delivery system expressing only spike protein, which focus the memory responses on the spike and shifts the responses to the inserts rather than the vectors in the immunodominance hierarchy. [20] [21] [22] Our study provided the first evidences on the safety and immunogenicity of a heterologous regimen with the inactivated vaccine and Ad5 vector-based vaccine against SARS-CoV-2 in human being. Although the 28-day homologous two-dose inactivated vaccine regimen was the least immunogenic of the four regimens in our study, this is a All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 6, 2021. ; https://doi.org/10.1101/2021.09.03.21263062 doi: medRxiv preprint licensed vaccine schedule which has hit above the minimum efficacy of 50%, and reduce over 86% of hospitalization and death in both phase 3 trials and post-license studies. 23 Up to now, at least four studies adopted heterologous prime-boost regimens have been 27 Only one of the studies reported that a higher reactogenicity was found associated with the heterologous prime-boost vaccination, and others did not. 28 The first limitation of this study is that only adults aged between 18-59 years were involved in, but not older adults, particularly those over 75 years of age, who are often immunocompromised or with coexisting conditions, and poorly respond to vaccines.

We are carrying out another study to evaluate the heterologous prime-boost vaccination with CoronaVac and Convidecia in the older population (NCT04952727).

Second, studies on the mechanism of the enhanced immune responses and the detailed B-and T cell activation associated with the heterologous prime-boost were not All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 6, 2021. ; https://doi.org/10.1101/2021.09.03.21263062 doi: medRxiv preprint performed, thus we can only have a speculation about the reasons why this regimen are more immunogenic. Third, we could not access the efficacy of the heterologous prime-boost vaccination regimen against COVID-19 diseases, and the protection of this regimen remain undetermined. But several previous studies found that binding and neutralizing antibodies correlated with COVID-19 risk and were most likely to be able to predict the vaccine efficacy. 29 Besides, the neutralizing antibody titers against delta variant B.1.617.2 was not reported. As the delta variant has become predominant variants of concern in many countries, whether the heterologous prime-boost regimen could potentially offer an additional protection to the delta variant over currently licensed two-dose inactivated vaccine schedule needs to be answered. At last, the relatively small number of participants in this study was insufficient to identify potential increase of risks for some rare but severe adverse reactions, particularly the immune-mediated events.

In conclusion, the heterologous prime-boost regimen with inactivated vaccine CoronaVac and ad5-vectored vaccine Convidecia were safe and highly immunogenic, increased both humoral and cellular immunity responses significantly, which could be useful for a third dose strategies to be administered to persons who have previously received two doses of inactivated vaccines.

The results supporting the findings in this study are available upon request from the corresponding authors.

All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in *2 participants were randomized to group A, but were wrongly administrated with an inactivated vaccine and then classified to group B. 1 participant was only primed one dose, but was wrongly classified into the population with two doses prime vaccination, and randomized to group A to receive one dose of ad5-based vaccine. We reclassified this participant to Group C. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in All rights reserved. No reuse allowed without permission.

perpetuity.

preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in Table 1 . Baseline characteristics of the participants in the modified full-analysis cohort.

Data are n (%) or means ± SD. The analysis was based on the modified full-analysis cohort, with some participants were reclassified into the right groups according to the 

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or GMFI (95% CI). n= the number of participants included the intervention modified intention-to-treat cohort. The P values are the results of comparison between the two treatment groups

Xue Wang, Jingxuan Wan, Junqiang Li, Tao Zhu are employees of CanSino Biologics. All other authors declare no competing interests.All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 6, 2021. ; https://doi.org/10.1101/2021.09.03.21263062 doi: medRxiv preprint