There are over 70 vaccines under scrutiny. And some are already showing good potential: among them the Ad5-nCov vaccine, tested in China on 108 volunteers, which was well tolerated and stimulated the production of neutralizing antibodies against Sars-Cov-2. But still caution is needed
The rush to a vaccine against the new coronavirus by many research groups around the world – they are already there more than 70 vaccines candidates – it’s almost a race against time or rather against Sars-Cov-2, in order to try to stop the Covid-19 pandemic as soon as possible. Every day we take a few steps forward and positive news about vaccines arrives from various groups. Today is the turn of a developed vaccine in China, in Wuhan – in acronym Ad5-nCov – that has passed phase 1 of the trial, proving to be well tolerated and also to stimulate the production of specific antibodies against Sars-Cov-2 and a good immune response of T cells. But this still does not indicate that it is effective in preventing Covid-19. The study, conducted by various institutes, including Hubei and the Jiangsu Province Centers for Disease Control and Prevention, is published on The Lancet.
Immunity humoral is cell phone
The researchers ran blood tests at regular intervals to find out if the vaccine is safe and if it managed to stimulate it either immunity humoral be cellular immunity. The humoral immune response is based on the activity of B lymphocytes and is mediated by the body’s production of specific antibodies against the virus in B lymphocytes. The other immune response, the cellular one, the defense mechanism against the virus is different because they are the same cells of the immune system – in particular T lymphocytes – and not the antibodies produced to fight the virus and destroy the infected cells. Ideally, a vaccine should stimulate both of these immune responses and not just the humoral one.
The vaccine in question is called Ad5-nCov given that the researchers used a adenovirus (type 5 – hence the abbreviation Ad5), weakened, a common cold-causing virus, used as a carrier to transport the genetic material of the new Sars-Cov-2 coronavirus.
The study evaluated the safety and the ability to produce an immune response that can block the virus. The researchers in Wuhan got involved 108 healthy volunteers, aged between 18 and 60, who did not have Covid-19 infection. The volunteers, divided into 3 groups, received the new low, medium and high dose Ad5 vaccine via intramuscular injection.
The results, from safety to potential
28 days after administration there has been no serious adverse reaction, although most participants experienced at least one mild or moderate undesirable effect within the first week of vaccination. The most common reactions are pain around the injection site, temperature, tiredness, headache and pain in the muscles. Only one participant reported high fever, marked fatigue, breathlessness and muscle pain, symptoms which however returned within 48 hours.
As for the immune response, the authors explained that after 14 days from administration in a single dose the experimental vaccine produced specific antibodies against Sars-Cov-2 and also good cellular response. “This makes him a potential candidate for further investigation”he stressed Wei Chen, from the Institute of Biotechnology in Beijing, who coordinated the study. “However, these results must be interpreted with caution“, adds the author, who recalls that being able to stimulate a good immune response it does not necessarily imply that the vaccine protects against the new coronavirus. In any case, the vaccine has passed phase 1 of the clinical trial, which has technical times – there are 3 phases, the first one serves to demonstrate the safety and tolerability of the drug and involves a still rather small sample of participants.
Other vaccines, where we are
Speaking of the clinical trial (on human volunteers), currently, on May 27, 2020 on the page Clinicaltrials.gov three clinical studies are active. Among these three, one is the one we talked about today, which has passed phase 1. The second, recently started, is its continuation, or experimentation in phase 2 of Ad5-nCov out of 508 healthy volunteers. Then there is a third clinical study (phase 1 and 2), conducted in the United Kingdom on 1,090 participants, is evaluating the vaccine ChAdOx1, also based on a adenovirus weakened that carries genetic material of Sars-Cov-2. The Oxford authors some time ago announced that it could have arrived, in the first few doses, already in autumn 2020, but still there is no certainty that this can happen.
But there is also no shortage promising results on animals, in preclinical research, which comes even before the clinical one: the news of a Chinese team that has identified powerful neutralizing antibodies. Among these, one, currently tested on macaques, has managed to inhibit the infection. The result was published on Nature. But it is not the only research with good results on animals: two studies on Science, for example, have shown the development of neutralizing antibodies against the virus and that i primates were not subject to a second infection.
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