Three Covid-19 clinical trials show promising preliminary results, increase hope for effective vaccines
A Phase 3 program is still needed to assess the ability of the vaccine to protect people from Covid-19, say experts
Three potential Covid-19 vaccines cleared an important hurdle in the vaccine development process. According to the preliminary results released on July 20, all of them appeared safe and induced an immune response. Though experts labeled these results promising, they caution that only phase 3 trials will offer answers on whether any of these vaccine candidates protect people from Covid-19.
One of the vaccine groups was the American giant Pfizer and the German-based BioNTech,.They published their results in a preprint format and is now being tested for accuracy. The development comes after the US-based Moderna released positive data last week. The vaccine maker is set to begin phase 3 trials next week.
For their phase 1/2 trial, the Pfizer-BioNTech team tested their potential vaccine on 60 healthy volunteers in Germany aged between 18 and 55 years. The aim was to check for an immune response -- antibodies and T cells -- along with safety before proceeding to phase 3, which test for the vaccine's efficacy. Antibodies are proteins that fight an invader and neutralize it while T cells kill infected human cells. The latter also holds a memory of the virus, helping the body fight a second infection. The team also tested their candidate in the US as well.
The vaccine named BNT162b1 is an mRNA based vaccine. It manipulates the body to make proteins that mimic the new coronavirus. These proteins, in turn, train the body by generating a protective immune response. Researches involved in the study recorded minor side-effects in the vaccinated volunteers. However, some of them developed flu-like symptoms and injection site-reactions, which resolved spontaneously.
"The preliminary data indicate that our mRNA-based vaccine was able to stimulate antibody as well as T-cell responses at remarkably low dose levels. We believe both may play an important role in achieving effective clearance of a pathogen such as SARS-CoV-2,” Dr. Özlem Türeci, CMO and Co-founder of BioNTech, said in a statement.
The team hopes to begin a global Phase 2b/3 safety and efficacy trial in late July. That trial may involve up to 30,000 healthy participants. The group has signed a deal to supply 30 million doses of their vaccine to the UK.
Meanwhile, a Chinese vaccine company named CanSino also released positive results. Their vaccine contains another virus that is modified to carry the genetic material of the new coronavirus. The candidate named Ad5-nCOV, which was tested on over 500 healthy individuals, is published in Lancet. The results show that the vaccine induces both antibodies and T cells.
None of the participants reported adverse side-effects. "In this study, most reactions reported post-vaccination were mild or moderate. Although the proportions of participants who had adverse reactions such as fever, fatigue, and injection site pain were significantly higher in vaccine recipients than those in placebo recipients, adverse reactions within 28 days were generally not severe, and resolved within a short period of time," the researchers wrote in their study.
The third group, Oxford and its pharma partner AstraZeneca, also published their findings in Lancet. The vaccine is a modified version of a chimpanzee virus, which contains parts of the new coronavirus. The researchers recruited 1077 healthy participants between the ages of 18 and 55 for study.
The vaccine generated T cells and antibodies targeting the new coronavirus. It caused some side-effects, including pain, feeling feverish, chills, muscle ache, headache, and malaise. Paracetamol helped resolved these signs, the researchers added.
In an editorial, two vaccine researchers from Johns Hopkins University, Naor Bar-Zeev, and William Moss commented on the Oxford and the Chinese study. They said: “The results of both studies augur well for phase 3 trials, where the vaccines must be tested on much larger populations of participants to assess their efficacy and safety.
"These encouraging results support further evaluation of this candidate vaccine in our ongoing large scale Phase III program, that is still needed to assess the ability of the vaccine to protect people from Covid-19, "Professor Sarah Gilbert, Professor of Vaccinology, at the University of Oxford Jenner Institute and co-author of the study said in a statement.