Since the very beginning of coronavirus outbreak in late 2019, the scientists and researchers have been putting their relentless efforts in developing an effective vaccine for the contagious virus.
But developing a vaccine normally takes years as the candidate must go through some specific tests before being injected into human body.
It has been nearly a year since the first coronavirus case was reported in China's Wuhan province in December last.
In the meantime, the world witnessed a significant progress in vaccine development as a total of 42 vaccine candidates developed by different countries entered the phase of clinical trial while 91 candidates are in pre-clinical stage.
According to latest data revealed by the World Health Organization (WHO), eleven of the 42 vaccines are now going through phase-3 of the clinical trial.
In the phase-3 efficacy trial, scientists inject the vaccine to thousands of people and wait to see how many become infected, compared with volunteers who received a placebo. These trials can determine if the vaccine protects against the coronavirus.
In addition, Phase 3 trials are large enough to reveal evidence of relatively rare side effects that might be missed in earlier studies, reports The New York Times.
Meanwhile, China and Russia have already approved vaccines on a limited scale without waiting for the results of Phase 3 trials ignoring concern from the experts.
The 11 leading vaccine candidates
1. The vaccine developed by US Biotechnology Company Moderna has been in phase-3 clinical trial since July 27.
The company began developing the vaccine candidate in January. The final trial is enrolling 30,000 healthy people at about 89 sites around the United States. Canada agreed in September to acquire 20 million doses.
2. The German company BioNTech entered into collaborations with Pfizer, based in New York, and the Chinese drug maker Fosun Pharma to develop a vaccine candidate. On July 27, the companies announced the launch of a Phase 2/3 trial with 30,000 volunteers in the United States and other countries including Argentina, Brazil, and Germany.
In an interim study, the companies reported that after getting the first dose, volunteers experience mostly mild to moderate side effects. On Sept. 12, Pfizer and BioNTech announced that they would seek to expand their U.S. trial to 43,000 participants. The following month, they gained permission to start testing the vaccine on children as young as 12 - the first American trial to do so.
3. Chinese company CanSino Biologics developed a vaccine, in partnership with the Institute of Biology at the country's Academy of Military Medical Sciences.
In May, they published promising results from a Phase 1 safety trial, and in July they reported that their Phase 2 trials demonstrated the vaccine produced a strong immune response.
In an unprecedented move, the Chinese military approved the vaccine on June 25 for a year as a "specially needed drug." Starting in August, CanSino began running Phase 3 trials in a number of countries, including Saudi Arabia, Pakistan and Russia.
4. The Gamaleya Research Institute of Russia in June launched clinical trials of a vaccine they called Gam-Covid-Vac.
On August 11, President Vladimir Putin announced that a Russian health care regulator had approved the vaccine, renamed Sputnik V, before Phase 3 trials had even begun.
The move drew huge criticism from health experts across the globe. Russia later walked back the announcement, saying that the approval was a "conditional registration certificate," which would depend on positive results from Phase 3 trials.
Those trials, initially planned for just 2,000 volunteers, were expanded to 40,000. In addition to Russia, volunteers were recruited in Belarus, the United Arab Emirates, and Venezuela.
5. The vaccine developed by US Company Johnson & Johnson completed phase 1 and 2 trials in July. Later in September, the company launched a phase-3 trial with up to 60,000 participants.
In August, the federal government agreed to pay $1 billion for 100 million doses if the vaccine is approved. The European Union reached a similar deal on Oct. 8 for 200 million doses. The company is aiming for production of at least a billion doses in 2021.
6. The British-Swedish company AstraZeneca and the University of Oxford developed a vaccine based on a chimpanzee adenovirus. A study on monkeys found that the vaccine protected the animals from the disease.
The vaccine began Phase 2/3 trials in England and India (where it's known as Covishield).
7. The vaccine candidate prepared by US company Novavax entered the clinical trials in May.
After getting promising results from preliminary studies in monkeys and humans, Novavax launched a phase-2 trial in South Africa in August.
The following month, Novavax launched a phase-3 trial enrolling up to 10,000 volunteers in the United Kingdom.
8. The Wuhan Institute of Biological Products developed an inactivated virus vaccine, which the state-owned Chinese company Sinopharm put into clinical tests. They launched phase-3 trials in the United Arab Emirates in July, and in Peru and Morocco the following month.
9. Chinese state-owned enterprise Sinopharm also takes step to test a second inactivated virus vaccine developed by the Beijing Institute of Biological Products. After running early clinical trials in China, they launched Phase 3 trials in the United Arab Emirates and Argentina.
On September 14, the UAE gave emergency approval for Sinopharm's vaccine to use on health care workers.
10. Sinovac Biotech, a private Chinese company, is testing another inactivated vaccine called CoronaVac. The company launched a phase-3 trial in Brazil in July, followed by others in Indonesia and Turkey.
In October, authorities in the eastern Chinese city of Jiaxing announced they were giving CoronVac to people in relatively high-risk jobs, including medical workers, port inspectors and public service personnel.
11. A vaccine that was developed in the early 1900s as a protection against tuberculosis is now being tested against the coronavirus by an Australian company. The Murdoch Children's Research Institute of Australia launched the Phase 3 trial called the BRACE to see if the vaccine partly protects against the coronavirus.