Two Covid-19 vaccine candidates have been shown to be safe for humans and have produced strong immune reactions among patients involved in two separate clinical trials, doctors said Monday.
The first trial among more than 1,000 adults in Britain found that the vaccine induced “strong immune responses of antibodies and T cells” against the new coronavirus.
A separate trial in China involving more than 500 people showed that the majority had developed a widespread antibody immune response.
The studies, published in the medical journal The Lancet, are an important step on the road to a Covid-19 vaccine that is effective and safe for widespread use.
See: Coronavirus: How long does it take before we have a vaccine?
The study authors said they found few adverse side effects from vaccine candidates. However, they cautioned that more research was needed, especially among older adults, who are at a disproportionate risk of dying from Covid-19.
Co-author Sarah Gilbert of the University of Oxford said the results “are promising.”
“If our vaccine is effective, it is a promising option since this type of vaccine can be manufactured on a large scale.”
The pandemic has seen an unprecedented mobilization of funds and research to rush through a vaccine that can protect billions of people worldwide.
Both studies were phase 2 trials, evaluating whether the vaccine elicits an immune response and whether patients can tolerate it well.
For their test, the Oxford team used a genetically modified strain of the common cold virus that infects chimpanzees.
They manipulated the virus to train cells to recognize the viral peak protein, helping to teach the immune system to recognize Covid-19.
In addition to developing antibodies in their blood, patients who received the vaccine were found to develop a robust T-cell response, which helped their bodies identify and neutralize the virus.
“The immune system has two ways to find and attack pathogens: antibody responses and T cells,” said Andrew Pollard, a member of the Oxford team.
“This vaccine is intended to induce both, so it can attack the virus when it is circulating in the body, as well as attack infected cells.”
The Oxford team found that among the approximately 500 patients who received the vaccine, their immune response peaked around 14 days and decreased slightly on day 56, the end of the study period.
The other 500 patients received the meningitis vaccine as a placebo.
More than one dose?
The second trial, led by China’s Jiangsu Provincial Center for Disease Control and Prevention, used a modified weakened human cold virus to deliver genetic material that teaches cells to recognize the new coronavirus.
Two groups of patients received a high or low dose of the vaccine.
More than 90 percent of people in both groups showed antibody or T-cell immune responses between 14 and 28 days after the vaccine.
Side effects in both trials were moderate, but the authors of the Chinese study said they needed to assess the vaccine’s safety in older patients.
“Older people … are an important target population for a Covid-19 vaccine,” said Wei Chen of the Beijing Institute of Biotechnology.
“An additional dose may be needed to induce a stronger immune response in the elderly population.”
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