A closer look at the COVID-19 vaccine front-runners


As the COVID-19 pandemic continues to wreak havoc on public health and the global economy, the search for a vaccine has taken on an intensity never seen before in the history of medical research.

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After 5 months of global deaths, border restrictions and economic shut downs, many countries have begun implementing tentative plans to ease lockdown measures. While this is viewed positively by many, there remains much unease for fear of reversing the progress made so far in reducing the spread of the virus, with the US’s top infectious diseases expert Anthony Fauci (NIAID) recently encouraging caution, warning that the coronavirus pandemic is far from over, despite the easing of restrictions.

It is because of this that a COVID-19 vaccine is widely regarded as the panacea for a fast track to normal life. There are currently over 120 vaccine candidates in development, with ten already in clinical trials. Researchers engaging in this race, or more appropriately termed, marathon, face a unique set of challenges as they try to achieve this goal.

While it will be some time before we know whether any of these vaccines are effective in the long run, initial trial results have been promising, and the front-runners are emerging. Here they are:

Oxford University, AstraZeneca

The University of Oxford (UK) was well-placed to begin developing a SARS-CoV-2 vaccine, having already worked on vaccines for MERS and SARS.

Oxford’s vaccine, AZD1222, otherwise known as ChAdOx1 nCoV-19, uses a weakened adenovirus as a vector infused with the DNA sequence for the coronavirus spike protein.

A large Phase I clinical trial began in late April. More than 1000 participants have already been dosed and follow up is currently ongoing. In order to determine how well the vaccine induces immune responses in older adults, the team are now initiating Phase II studies enrolling up to 10,260 volunteers.

Following landmark agreements with the Coalition for Epidemic Preparedness Innovations (CEPI), Gavi the Vaccine Alliance and the Serum Institute of India, the university and industry partnership have secured funding that will allow them to manufacture and distribute their vaccine globally, should it be successful.


Another company to have made a head start is Sinovac (Beijing, China), which was previously developing a vaccine against SARS. Their CoronaVac was developed using a more traditional method, consisting of a chemically inactivated version of SARS-CoV-2.

The company has already demonstrated that their candidate can protect monkeys from infection during Phase II trials, adding that it’s 99% confident that the vaccine will work against COVID-19. They are now planning Phase III trials while building a commercial production plant to manufacture up to 100 million doses of the vaccine per year.


Moderna (MA, USA) is another runner selected as part of the US government’s Operation Warp Speed, and their mRNA-1273 vaccine has certainly lived up to expectations so far, having rocketed from a computer design in mid-January to a clinical trial only 3 months later.

This candidate is an mRNA vaccine, which comprises a nanoparticle containing genetic instructions for the coronavirus spike protein.

Not much has been given away yet in terms of results, but a Phase III study is set to commence in July. There remains speculation that while the vaccine may be quick and easy to produce, no mRNA vaccine has yet been proven to prevent disease, let alone on a global scale.

CanSino, Beijing Institute of Biotechnology

Besides Oxford, one other viral vector vaccine has made it to human trials. This candidate comes from CanSino Biologics (Tianjin, China), and like Moderna, it has been quick off the mark, as the first to reach Phase I clinical trials back in April.

The initial results have demonstrated that the vaccine is safe at lower doses and that it did indeed generate an immune response in the 108 participants, though it’s not yet certain whether the vaccine’s effects would be protective against SARS-CoV-2 infection.

Phase II testing is already underway in order to determine whether these results can be replicated over a longer period and with a larger sample size.

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Inovio Pharmaceuticals 

Inovio’s (PA, USA) INO-4800 is a DNA vaccine encoding the coronavirus spike protein, which coaxes cells to produce coronavirus proteins, thereby triggering an immune response. In order to deliver the DNA to the cells, Inovio uses a method termed electroporation, in which a brief electrical pulse opens small holes in the cells.

A 40-patient Phase I trial is currently underway, with results expected later on this month. Plans are also in place to initiate a Phase II/III efficacy trial within the next couple of months, pending regulatory approval.

The main hurdle to clear, should the vaccine prove successful, will be manufacturing, as the company has only committed so far to produce 1 million doses by the end of the year.

BioNTech, Pfizer

Another company selected as part of Operation Warp Speed, Pfizer (NY, USA) and their German partner BioNTech (Mainz, Germany) started developing their candidates in March. Like Moderna, they are pushing the swift yet unproven mRNA technique, but have this time developed multiple candidates, each of them representing a different combination of mRNA and a target antigen.

Pfizer and BioNTech have since begun Phase I and Phase II clinical trials in Germany and the US, with further tests to follow. Although the vaccine is still under trial, the company is already preparing plans to manufacture millions of doses starting this year, with Pfizer’s CEO stating that he hopes to have a vaccine available for use by the end of October.


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