The first vaccine against COVID-19 to reach phase 1 of the clinical trial issafe, well tolerated and capable of generating an immune response against SARS-CoV-2 in humans, according to new research published in the journal The Lancet. Open trial in 108 healthy adults shows promising results after 28 days.
The final results will be evaluated in six months. In any case, more testing is needed to see if the immune response it elicits effectively protects against SARS-CoV-2 infection.
"These results represent an important milestone. The trial shows that a single dose of the new COVID-19 vaccine vectorized by adenovirus type 5 (Ad5-nCoV) produces specific antibodies against the virus and T cells in 14 days, making it a potential candidate for further research. " , explains the person in charge of the work, Wei Chen, of the Beijing Institute of Biotechnology, China.
"However, these results should be interpreted with caution. The challenges in developing a COVD-19 vaccine are unprecedented, and the ability to trigger these immune responses does not necessarily indicate that the vaccine will protect humans from COVID-19. This result shows a promising vision for the development of COVID-19 vaccines, but We are still a long way from making this vaccine available to everyone."Says the scientist. At present, There are more than 100 COVID-19 candidate vaccines in development worldwide.
The new Ad5 vectorized COVID-19 vaccine evaluated in this trial is the first to be tested on humans. It uses a weakened common cold virus (adenovirus, which easily infects human cells but is unable to cause disease) to deliver genetic material that encodes the leading SARS-CoV-2 protein to cells. These cells make the tip protein and travel to the lymph nodes, where the immune system creates antibodies that recognize that tip protein and fight the coronavirus.
The trial assessed the safety and ability to generate a immune response of different doses of the new Ad5-nCoV vaccine in 108 healthy adults between 18 and 60 years old they were not infected with SARS-CoV-2. Volunteers from a Wuhan, China center were enrolled and assigned a single intramuscular injection of the new Ad5 vaccine at a low, medium or high dose.
The researchers tested the volunteers' blood at regular intervals after vaccination to see if the vaccine stimulated both arms of the immune system: the body's "humoral response" (the part of the immune system that produces neutralizing antibodies that can fight infection and it could offer a level of immunity), and the body's cell-mediated arm (which relies on a group of T cells, rather than antibodies, to fight the virus). The ideal vaccine could elicit both antibody and T cell responses to defend against SARS-CoV-2.
The vaccine candidate was well tolerated at all doses, with no serious adverse events reported within 28 days of vaccination.. Most adverse events were mild or moderate, with 83 percent (30/36) of those receiving low and medium doses of the vaccine and 75 percent (27/36) in the high-dose group reporting at least one adverse reaction within 7 days of vaccination.
Two weeks after vaccination, all dose levels of the vaccine triggered some level of immune response in the form of binding antibodies (which can bind to the coronavirus but do not necessarily attack it - low dose group 16/36, 44%; medium dose 18/36, 50%; high dose 22/36, 61%), and some participants had detectable neutralizing antibodies against SARS-CoV-2 (low dose group 10/36, 28%; medium dose 11/36, 31%; high dose 15/36, 42%).
After 28 days, most participants quadrupled the binding antibodies (35/36, 97% in the low-dose group; 34/36 (94%) in the medium-dose group, and 36/36, 100% in the group high dose), and half (18/36) of the participants in the low and medium dose groups and three quarters (27/36) of those in the high dose group showed neutralizing antibodies against SARS-CoV-2 .
The Ad5-nCoV vaccine also stimulated rapid T-cell response in most volunteers, which was greater in those who received the highest and average doses of the vaccine, with levels peaking at 14 days of vaccination (low dose group (30/36; 83.3%), medium dose group (35/36, 97.2%) and high dose group (35/36, 97.2%) at 14 days).
Other analyzes showed that 28 days after vaccination, most recipients showed a positive T-cell response or had detectable neutralizing antibodies against SARS-CoV-2 (low dose group 28/36, 78%; medium dose group 33/36, 92%; high dose group 36/36, 100%).
However, the authors point out that both the antibody and the T cell response could be reduced by the high pre-existing immunity to adenovirus type 5 (the vector / carrier of the common cold virus); in the study, 44 to 56 percent of trial participants had high pre-existing immunity to type 5 adenovirus and had a less positive antibody and T-cell response to the vaccine.
"Our study found that pre-existing immunity to Ad5 could slow down rapid immune responses to SARS-CoV-2 and also reduce the peak level of responses. Furthermore, the high pre-existing immunity to Ad5 could also have a negative effect on the persistence of immune responses elicited by the vaccine."Says Feng-Cai Zhu of the Jiangsu Provincial Center for Disease Control and Prevention in China, who led the study.
The authors note that The main limitations of the trial are the small sample size, the relatively short duration and the lack of a randomized control group.This limits the ability to detect more rare adverse reactions to the vaccine or to provide strong evidence of its ability to generate an immune reaction. More research will be needed before this test vaccine is available to everyone..
A randomized, double-blind, placebo-controlled phase 2 trial of the Ad5-nCoV vaccine has been started in Wuhan to determine if the results can be replicated, and if there are any adverse events up to 6 months after vaccination, in 500 adults. healthy, 250 volunteers who received a medium dose, 125 who received a low dose, and 125 who received a placebo as a control. For the first time, this will include participants over the age of 60, a significant vaccine target population.
More than 10,000 people will participate in a trial for a vaccine
Oxford University announced today that will expand the participation in vaccine tests to more than 10,000 people designed to combat the coronavirus and will include among them individuals over 70 and children aged between 5 and 12 years.
This British university, through the Jenner Institute for Vaccine Research, The first phase of testing began last April with a thousand healthy subjects under the age of 56, who are now joined by more than 10,200 people in the second, including the new age groups.
“There was already a lot of interest from people over 55 to participate in the first phase of the study, but they could not be selected. Now we can include older age groups to continue with the vaccine evaluation."He explained to the chain BBC Sarah Gilbert, Professor of Virology at the Jenner Institute.
In addition to those over the age of 70 and children between the ages of five and 12, experts will also study the effect that various treatments for COVID-19 have on the immune system in subjects between the ages of 56 and 69.
Specific, researchers will supply participants with doses of different experimental vaccines, such as the “ChAdOx1 nCoV-19”, to later compare the differences between one treatment and another between the groups.
Experts at the Jenner Institute estimate that this study could take anywhere from two to six months, depending on how many individuals are exposed to the virus.
(With information from Europa Press and EFE)
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