COVID-19 vaccines are yet to successfully finish the race

There has been significant development in COVID-19 vaccine discovery since the emergence of the current SARS outbreak. ChAdOx1 nCoV-19 vaccine has successfully completed its phase I/II trial and has demonstrated its immunogenicity and safety in about 1000 human volunteers from five centers in the UK. ChAd Ox1 nCoV-19 vaccine is a joint venture of Oxford University, British pharmaceutical giant AstraZeneca, and IQVIA, a contract research organization. The results of the single-blind, randomized controlled trial which was recently published in The Lancet [July 20, 2020] have delivered a ray of hope during this ominous state of affairs. Despite this encouraging results, we do not yet fully know about immunity to the novel virus. It seems that both antibody and T cell immunity are important, and this vaccine triggers both responses. However, the clinical usefulness of the vaccine will only become evident after the completion of larger human trials that are happening now.

The results of a phase 2 trial on a recombinant adenovirus type-5-vectored COVID-19 vaccine has also been published recently in The Lancet [July 20, 2020]. This study was randomized, double-blind, and placebo-controlled that included 508 healthy volunteers from a single center in China. The vaccine was showed to trigger immune response after 28 days in more than 96% of those who received either low-dose or high-dose intramuscular injection in the arm. Adverse reactions were common with both doses of vaccine, however, reactions were only mild and transient. Fatigue, fever, and headache were common.

Although these vaccines proved their immunogenicity, it is not known how strong the immune response needs to be to protect against SARS-CoV-2; therefore some of the vaccines being developed may not work at the end of the day.

There are several other vaccines that are behind these two vaccines. At the time of writing this article, 142 vaccines have been discovered and are being under investigation at different stages of pre-clinical development. Another sizeable number of vaccines (n=24) are under clinical development. To be inch-perfect, two vaccines are undergoing phase 3 trials, another 3 vaccines are under phase 2, another 10 vaccines are undergoing combined phase I/II trials and nine other vaccines are in their early clinical development (phase 1).

Several biotechnology companies, pharmaceutical companies and academic institutions are in the race to bring their vaccine candidate to clinical use. These companies and institutions are focusing on different approaches in vaccine development. Major types of vaccine currently under development include viral vaccine vector, DNA vaccine, RNA vaccine, live-attenuated vaccine, and protein-based vaccine.

Bharat Biotech has developed an indigenous whole-virion, inactivated vaccine (Covaxin) for COVID-19 which is in its phase I/II clinical trials. However, it is expected to take more than a year to complete clinical trials with this vaccine candidate.

Cadila Healthcare Limited, an Indian Pharmaceutical company has developed a DNA plasmid vaccine (ZyCov-D) to prevent this infection. This vaccine also is in its early clinical development stage.

Codagenix, Inc., a biotechnology company has collaborated with the Serum Institute of India, Ltd. in developing a vaccine against the novel virus. The company used viral deoptimization to synthesize this rationally designed live-attenuated vaccine. However, the vaccine is only in its pre-clinical stage.

Griffith, one of the Australia’s reputed research universities has partnered with the vaccine manufacturer, Indian Immunologicals to develop a vaccine. This partnership has also utilized codon deoptimization technology to develop the live-attenuated vaccine which is in its pre-clinical stage currently. 

It is not yet known when an effective vaccine would become available in pharmacy shelves, although WHO hopes that one will be available by October 2020.

 References:

1. Folegatti PM, Ewer KJ, Aley PK, Angus B, Becker S, Belij-Rammerstorfer S, et al. Safety and immunogenicity of the ChAdOx1 nCoV-19 vaccine against SARS-CoV-2: a preliminary report of a phase 1/2, single-blind, randomised controlled trial. The Lancet [Internet]. 2020 Jul 20 [cited 2020 Jul 21];0(0).

2. Zhu F-C, Guan X-H, Li Y-H, Huang J-Y, Jiang T, Hou L-H, et al. Immunogenicity and safety of a recombinant adenovirus type-5-vectored COVID-19 vaccine in healthy adults aged 18 years or older: a randomised, double-blind, placebo-controlled, phase 2 trial. The Lancet [Internet]. 2020 Jul 20 [cited 2020 Jul 24];0(0).

3. Draft landscape of COVID-19 candidate vaccines [Internet]. [cited 2020 Jul 24].