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A phase II clinical trial of a COVID-19 vaccine candidate, conducted in China, has found it is safe and causes an immune reaction, a study published in The Lancet says.
Researchers, for example those from the Center for Disease Control and Prevention, said the trial sought to assess the safety and immunogenicity of this vaccine candidate.
They said the results provide information from a wider group of participants than their earlier phase I trial, such as a small sub-group of participants aged over 55 years and older.
However, the researchers cautioned that no participants at the current trial were exposed to this novel coronavirus, SARS-CoV-2, after vaccination. So they said it isn’t possible for the present study to determine whether the vaccine candidate effectively protects against SARS-CoV-2 disease.
From the trial, the researchers used a diminished human common cold virus (adenovirus, which infects cells easily but is incapable of causing illness ) to provide the hereditary material that codes for the novel coronavirus spike protein into the cells.
The scientists stated these cells then generated the coronavirus spike protein, and go to the body’s lymph nodes where the immune system creates antibodies.
They said these antibodies then reevaluate the spike protein and also fight off the coronavirus.
“The Beijing approach is based on the backbone of a traditional human, common-cold virus to which many people have pre-existing antibodies and they therefore make a lesser response in some people to the vaccine because people have preexisting antibodies to their vector, so may clear it before it has a opportunity to work correctly,” explained Danny Altmann, Professor of Immunology at Imperial College London in the united kingdom, who is unrelated to the research team.
According to the scientists, 508 participants participate in the trial of this new vaccine candidate.
Of these, they said 253 individuals received a higher dose of this vaccine, 129 received a very low dose, and 126 received a dummy treatment, a placebo.
The analysis noted that about two thirds of those participants were 18-44 years old, a quarter were aged 45-54 decades, and 13 percent were 55 years or older.
The participants were monitored for immediate adverse reactions for 30 minutes following injection, and have been followed closely for any injection-site reactions in 14- and 28-days post-vaccination, the study noted.
It stated serious adverse events reported by participants during the whole study period were also documented, and blood samples have been taken from them before therapy, and 14- and 28-days post-vaccination to measure antibody responses.
The findings demonstrated that 95 percent (241/253) of those participants in the high dose group, and 91 percent (118/129) of these in the low dose group demonstrated either T cell or antibody immune reactions daily 28 post-vaccination.
According to the researchers, the vaccine triggered a neutralising antibody response in 59 per cent (148/253) and 47 percent (61/129) of the participants, and transmitting antibody reaction in 96 per cent (244/253) and 97 percent (125/129) of participants, in the low and high dose groups, respectively, by day 28.
The analysis mentioned that the percentage of participants that had some adverse reactions such as fever, exhaustion and injection-site pain were considerably higher in vaccine recipients, compared to those who were given the placebo.
They stated the most common serious reaction was fever.
The investigators cautioned that pre-existing immunity to the human adenovirus that was used as the vector (the Ad5 vector) with this particular vaccine, and increasing age could partially hamper the specific immune responses to vaccination, especially for its antibody responses.
“Since older individuals face a higher risk of severe illness and even death connected with COVID-19 infection, they’re an important target population for a COVID-19 vaccine. It’s possible that an extra dose may be needed in order to cause a stronger immune response in the elderly population, but additional study is underway to evaluate this,” said study co-author Wei Chen in the Beijing Institute of Biotechnology at China.
Since the trial participants were not exposed to this coronavirus subsequent to vaccination, the scientists stated it is not possible for the present research to find out the effectiveness of the candidate vaccine.
They said it’s also not possible to say from the present research if there are any risks linked to the antibody induced by vaccination when exposed to the novel coronavirus.
