The race for a vaccine against the new coronavirus by many research groups around the world – there are already more than 70 candidate vaccines – is almost a race against time or better 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 vaccine developed in China, in Wuhan – in the initials Ad5-nCov – which has passed the 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 in The Lancet.
Humoral and cellular immunity
The researchers carried out blood tests at regular intervals to see if the vaccine is safe and if it succeeds managed to stimulate both the immunity humoral or 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 as the immune system – especially 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 since the researchers used an adenovirus (type 5 – hence the abbreviation Ad5), a weakened, common cold-causing virus, used as a vector to transport the genetic material of the new coronavirus Sars -Cov-2 .
The study assessed the safety and ability to produce an immune response that can block the virus. Researchers in Wuhan 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
There was no serious adverse reaction 28 days after administration , although most participants had at least one mild or moderate unwanted effect within the first week of vaccination. The most common reactions are pain around the injection site, fever , fatigue, 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.
Regarding the immune response, the authors explained that after 14 days of administration in a single dose, the experimental vaccine produced specific antibodies against Sars-Cov-2 and also a good cellular response . “This makes him a potential candidate for further investigation,” said Wei Chen , of the Beijing Institute of Biotechnology, 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 does not necessarily implythat 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 are we?
Speaking of the clinical trial (on human volunteers), at the date of May 27, 2020, three clinical trials are active on the Clinicaltrials.gov page . Among these three, one is the one we talked about today, which has passed phase 1. The second , which has just started, is its continuation, that is the experimentation in phase 2 of Ad5-nCov on 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 ChAdOx1 vaccine , also based on an adenovirusweakened 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 there is still no certainty that this can happen.
But there are also promising results on animals , in preclinical research, which comes even before the clinical one: news has just arrived from a Chinese team that has identified powerful neutralizing antibodies . Among these, one, which has so far been tested on macaques, has managed to inhibit the infection. The result was published in Nature . But it’s not the only research with good results on animals: two studies in Science , for example, showed the development of neutralizing antibodies against the virus and that primates were not subject to a second infection .