The race for developing the first COVID-19 vaccine may be over, but the race to develop the best vaccine is far from finished.

Currently, nine different vaccines are in circulation and being administered around the world. Each of the vaccines is made up of different properties and has different characteristics, including their efficacy, safety, cost or method of use.

According to scientific experts, history suggests that the first vaccine produced does not automatically make it the best, as it may not meet all the requirements.

In fact, having numerous varying vaccines in development increases the chances of having more than one successful vaccine that is proven to be safe and effective for the intended population, and the best to use.

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So, what are the ideal properties or characteristics of a vaccine?

The World Health Organization's chief scientist, Soumya Swaminathan, lists the benchmarks for the perfect vaccine as:

- A 50 percent minimum efficacy rate, ideally above 70 percent.

- Safe for different groups of people, including pregnant women.

- Ideally given in a single dose.

- Provide long term protection for several years.

- Stored at room temperature or in the fridge.

- Easy to scale and manufacture.

- Affordable

- Non-injectable, for example, a nasal vaccine or other modes of administration.

No single vaccine currently being administered ticks all the benchmarks listed by the WHO, but a few of them, including the Pfizer/BioNTech jab, which was approved for use by the European Union, have more than one of these ideal properties.

However, new vaccines currently at various stages at development could provide the answer, and could build on including all the ideal properties for the vaccine.

The WHO's Soumya Swaminathan said "I think the latest... we had something like 65 vaccine candidates in clinical phases of testing, 15 of them were in the late stage, phase three, and another 170 or so in pre-clinical development." 

Experts explain the reason that so many vaccines need to be developed is because all of them contain properties that are a little different. 

"The first vaccine to go out, the Pfizer vaccine, which showed a very high efficacy in the clinical trials – it's a new platform technology, the mRNA vaccine – the drawback is that it requires an ultra cold chain. It requires very low temperatures, minus 70, minus 80 degrees Celsius to be stored. That's a problem in many countries," Swaminathan explained.

"So there are other vaccines in development which may be affected with a single dose. There's one in development that's a nasal vaccine. It may be possible to give it through inhalation. 

"And so there are vaccines in development which could actually be scaled up at a much more affordable cost. So there may be many vaccines that have advantages over the first generation," she added.