Researchers around the world are racing to develop a vaccine against Covid-19, with more than 140 candidate vaccines now tracked by the World Health Organization (WHO). Vaccines normally require years of testing and additional time to produce at scale, but scientists are hoping to develop a coronavirus vaccine within 12 to 18 months. Vaccines mimic the virus – or part of the virus – they protect against, stimulating the immune system to develop antibodies. They must follow higher safety standards than other drugs because they are given to millions of healthy people. How are vaccines tested? In the pre-clinical stage of testing, researchers give the vaccine to animals to see if it triggers an immune response. In phase 1 of clinical testing, the vaccine is given to a small group of people to determine whether it is safe and to learn more about the immune response it provokes. In phase 2, the vaccine is given to hundreds of people so scientists can learn more about its safety and correct dosage. In phase 3, the vaccine is given to thousands of people to confirm its safety – including rare side effects – and effectiveness. These trials involve a control group which is given a placebo. Sinovac Chinese company Sinovac is developing a vaccine based on inactivated Covid-19 particles. The vaccine has shown a promising safety profile in the early stages of testing and is now moving into Phase 3 trials in Brazil. Wuhan Institute of Biological Products/Sinopharm Beijing Institute of Biological Products/Sinopharm University of Oxford/AstraZeneca The University of Oxford vaccine is delivered via a chimpanzee virus, called the vaccine vector. The vector contains the genetic code of the protein spikes found on the coronavirus and triggers a strong immune response in the human body. The vaccine is in a combined phase 2/3 trial in the UK and has recently gone into phase 3 trials in South Africa and Brazil. CanSino Biologics Inc./Beijing Institute of Biotechnology The vaccine developed by Chinese company CanSino Biologics and the Beijing Institute of Biotechnology – a university close to the Chinese military – reportedly showed promising results in phase 2 testing, although no data from the trial has been published. In a world first, the vaccine has now been approved for military use, but it is unclear how broadly it will be distributed. Anhui Zhifei Longcom Biopharmaceutical/ Institute of Microbiology, Chinese Academy of Sciences Moderna/NIAID American biotech company Moderna is developing a vaccine candidate using messenger RNA (or mRNA for short) to trick the body into producing viral proteins itself. No mRNA vaccine has ever been approved for an infectious disease, and Moderna has never brought a product to market. But proponents of the vaccine say it could be easier to mass produce than traditional vaccines. Inovio Pharmaceuticals/ International Vaccine Institute Osaka University/ AnGes/ Takara Bio Genexine Consortium Cadila Healthcare Limited Bharat Biotech Institute of Medical Biology, Chinese Academy of Medical Sciences Novavax Kentucky Bioprocessing, Inc BioNTech/Fosun Pharma/Pfizer Gamaleya Research Institute Clover Biopharmaceuticals Inc./GSK/Dynavax Vaxine Pty Ltd/Medytox University of Queensland/CSL/Seqirus Imperial College London Curevac People"s Liberation Army (PLA) Academy of Military Sciences/Walvax Biotech. Medicago Inc. University of Melbourne/Murdoch Children’s Research Institute The Murdoch Children’s Research Institute in Australia is conducting a phase 3 trial using a nearly 100-year-old tuberculosis vaccine. The vaccine is not thought to protect directly against Covid-19 but might boost the body’s non-specific immune response. Source: WHO. Last updated 23 July