China's first Ad5-nCoV COVID-19 vaccine was rolled out on Friday. One of the developers of the single-dose vaccine said that the annual production capacity can reach 500 million doses, which means 500 million people can be vaccinated in a year. Phase-I clinical trials of the vaccine started on March 16, 2020, making it the world's first COVID-19 candidate vaccine that entered clinical trials. The Ad5-nCoV vaccine is a recombinant adenovirus vector vaccine jointly developed by CanSino Biologics and researchers from the Institute of Military Medicine under the Academy of Military Sciences led by Chen Wei. Chen is an infectious disease expert and a researcher at the Institute of Military Medicine under the Academy of Military Sciences. Unlike inactivated vaccines, Ad5-nCoV is effective with a single dose and can bring dual protection ̶ humoral and cellular immunity ̶ at the same time. It is the only single-dose COVID-19 vaccine that has been given a conditional approval to be rolled out in China, state broadcaster China Central Television (CCTV) reported on Friday. People can get desirable protective effect after 14 days of inoculation. The protective effect can last at least six months after a single-dose inoculation and it can increase immune response by 10 to 20 times if the second dose is taken half a year after the first one, Chen told CCTV in an exclusive interview on Friday. "We have data for six months so far to prove the vaccine's efficacy People don't need to take another dose within the first six months after their first inoculation. What if the epidemic is not over after six months? We have also developed the vaccine so that its effect is strengthened even after six months," Chen said. According to data, Chen and other researchers predicted that the vaccine's effect can last two years after two doses. The most important feature of the vaccine is that it can be produced fast and on a large scale, Chen said. The vaccine showed full protection against severe-illness morbidity in Pakistan, Chen said, noting that it can achieve more than 90 percent protection against severe-illness. The vaccine showed 90.98 percent efficacy rate in preventing severe diseases in its interim analysis. And it's effective in preventing 65.7 percent of symptomatic diseases in clinical trials conducted in multiple countries including Pakistan, Faisal Sultan, special assistant to the Pakistani Minister on Health, announced in early February. Chen said no serious adverse reactions associated with the vaccine have been reported in the vaccinated population so far, including those in extreme environments. And no specific adverse events have been reported that are different from those of other vaccines. The Ad5-nCoV vaccine is actually mature and reliable. The vaccine with such technology has already been used for Ebola virus in 2014, Chen said. People aged under 18 and over 60 are not allowed to take the other approved vaccines without conditional approval. However, the Ad5-nCoV vaccine is different. Ad5-nCoV's Phase-II and Phase-III trials all involved elder participants as people aged over 55 or 60 have a higher morbidity of severe illness, Chen said. The oldest volunteer was a man surnamed Xiong whose antibody tested positive after the clinical trial results were revealed, this gave researchers great confidence, Chen noted. She also said they have safety data of clinical trials for people aged 6-18 which are being reviewed by China's National Medical Products Administration. A PhD volunteer took the vaccine on February 29, 2020, the same day as Chen. And she had given birth to a baby one week earlier. "She and her baby are healthy now," Chen said. Since the vaccine can be transported and stored at 2C-8C, Chen hopes that the vaccine won't require cold-chain logistics. She also said they have finished the clinical trials around the world and will soon release the results. In China there are two types of COVID-19 vaccines ̶ inactivated and Ad5-nCoV vaccines. When asked which one people should choose, Chen said those who want to take fewer doses and get faster immune response should choose the Ad5-nCoV. As other variants of the virus have been found in other parts of the world, Chen said they will follow the safety of the vaccine over the long term after the rollout, and they will also track its effectiveness against the new variants. She also stated that they have started to develop a vaccine against the new variants. When asked what the level of China's vaccine research and development is in the world, Chen said, "There is no doubt we are in the first group." "There are few other countries that can reach the level that China has reached," she noted. "We are neither arrogant nor condescending. We also learn more from others in order to produce safer vaccines. We must have confidence in our science and technology," she remarked.