The open-label trial in 108 healthy adults demonstrates promising results after 28 days - the final results will be evaluated in six months.
"These results represent an important milestone. The trial demonstrates that a single dose of the new adenovirus type 5 vectored Covid-19 (Ad5-nCoV) vaccine produces virus-specific antibodies and T cells in 14 days", said study co-author Wei Chen from the Beijing Institute of Biotechnology.
Bypassing clinical trials for a potential SARS-CoV-2 vaccine would be "catastrophic", says Science Advances deputy editor Douglas Green in this Editorial. However, the researchers cautioned that the results should be interpreted carefully. "The ability to trigger these immune responses does not necessarily indicate that the vaccine will protect humans from COVID-19".
Since January, when we began to see the COVID-19 epidemic grow in Wuhan, the scientific and pharmaceutical community has been on a quest to develop a vaccine that will end the pandemic, avert further outbreaks and prevent deaths. This genetic material provides instructions for making the "spike protein" on the surface of SARS-CoV-2. These cells then produce the spike protein, and travel to the lymph nodes where the immune system creates antibodies that will recognize that spike protein and fight off the coronavirus. The volunteers were divided into three groups of 36 and the vaccine was given intramuscularly with a single shot in increasing doses to the three groups - low dose (5 x 1010 viral particles per 0.5 mL vial), middle dose (1 x 1011viral particles per 1 mL vial) and high dose (1 x 1011 viral particles per 1.5 mL vial). Randomized placebo-controlled studies are needed to clarify the risks and benefits of the decades-old drug in the treatment of COVID-19, the researchers said.
They added that an ideal vaccine candidate generates both antibody and T cell responses to defend against SARS-CoV-2.
The researchers found that the Ad5 vaccine candidate was well tolerated at all doses with no serious side effects within 28 days of vaccination.
The researchers tested three doses and said the highest dose seemed to be the most effective. The most common reaction was pain at the injection site, along with redness, swelling, itching and induration.
The antibody titer (the measure used for antibody levels) for both binding and neutralising antibodies was directly proportional to the dose of the vaccine. Some of the participants, the researchers said, also exhibited a form of neutralising antibodies against SARS-CoV-2.
Participants blood levels of neutralizing antibodies reached their peak by the 28th day after they were injected.
The Ad5-nCoV vaccine also stimulated a rapid T cell response in the majority of volunteers, which was greater in those given the higher and middle doses of vaccine, the authors said. It comes after 28 days of observation in more than 100 healthy adults, who showed a notable immune response.
In these people, "their immune systems will essentially rear up and blunt the effect of the vaccine", said Dr. Kirsten Lyke, a vaccinologist at the University of Maryland who is leading another coronavirus vaccine trial.
The following is a brief roundup of some of the latest scientific studies on the novel coronavirus and efforts to find treatments and vaccines for COVID-19, the illness caused by the virus.
The study's authors also noted that their research is limited because of its small sample size and short duration, and it also lacked a control group.