Safety and immunogenicity of BBV152 (COVAXIN) SARS-CoV-2 Vaccine: Part 3- Study Results

This article will briefly describe the results of the study.

Results:

Of 897 individuals screened between 13 July 2020 and 30 July 2020, 375 were enrolled. Of those excluded, 133 were excluded as they were positive for SARS-CoV-2 by by serology or nucleic acid test and 153 were excluded on account of abnormal laboratory values.

Among the enrolled participants 100 were randomly assigned to the three vaccine groups, while 75 were assigned to the control group (Algel only).

Participants were similar across groups with respect to age, sex, Body Mass Index (BMI), and vital signs.

The local reactions reported by study participants are shown in Table 1.

Table 1. Local reactions to COVAXIN

The systemic reactions reported by study participants are shown in Table 2.

Table 2. Systemic reactions to COVAXIN

There were no serious adverse events causally related to the vaccine.

IgG tires (Geometric Mean titres [GMTs]) to all epitopes (spike protein, receptor-binding domain, and nucleocapsid protein) increased rapidly after administration of both doses. IgG titres (GMTs) were similar in the 3µg with Algel-IMDG and 6µg with Algel-IMDG groups. The mean isotyping ratios (IgG1/IgG4) were greater than 1 for all vaccinated groups, indicating a T-helper 1 bias.

Seroconversion

Table 3. Seroconversion after receiving COVAXIN

The overall incidence of solicited local and systemic adverse events was 14-21% in all vaccine-treated groups and similar to other inactivated SARS-CoV-2 vaccine candidates.

The study assessed an accelerated vaccination schedule (vaccination 2 weeks apart) and not routine schedule (vaccination 4 weeks apart). The 4-week schedule for BBV152 (3µg with Algel-IMDG, and 6µg with Algel-IMDG) is being assessed in a phase 2 trial in 380 volunteers.

Whole-virion inactivated vaccines adjuvanted with Algel (alum) may lead to T-helper 2 cell responses that lead to antibody-dependent enhancement or enhanced respiratory disease. To circumvent this concern of antibody-dependent enhancement, BBV152 is adjuvanted with Algel and a TLR7/8 agonist that results in immune responses that are biased to T-helper 1 cells.

Since some of the control group recipients seroconverted, post-vaccination titres may be slightly inflated (some vaccine recipients may have had natural exposure to SARS-CoV-2). No symptomatic COVID-19 cases were reported in the control group.

The authors do not report any data on persistence of vaccine-induced antibody responses or long-term safety outcomes. The results do not permit efficacy assessments either. Most of the study participants were men and from the same ethnic group. Therefore, generalisation of study results to other populations is not possible. The storage conditions (2-8 C) for the vaccine are compatible with existing cold-chain systems for immunization.

Further efficacy trials are needed to assess effectiveness and duration of protection.

Useful Links:

Link to the Lancet article:

https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30942-7/fulltext

Link to independent commentary on the above article (also published in The Lancet):

https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30988-9/fulltext

Link to fact sheet on COVAXIN issued by Bharat Biotech:

https://www.bharatbiotech.com/images/covaxin/covaxin-fact-sheet.pdf

Links to previous articles in this series:

https://communitymedicine4all.com/2021/01/24/safety-and-immunogenicity-of-bbv152-covaxin-sars-cov-2-vaccine-part-1-vaccine-basics/

https://communitymedicine4all.com/2021/01/27/safety-and-immunogenicity-of-bbv152-covaxin-sars-cov-2-vaccine-part-2-study-methods/

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