Chinese researchers report on the first human trial of a candidate vaccine for COVID-19.
COVID-19 vaccine urgently required for long-term pandemic solution
SARS-CoV-2, the virus causing the COVID-19 pandemic, has spread rapidly around the world since the first infections were reported at the end of 2019. The WHO situation report at the beginning of May 2020 estimated that the virus had infected over 4.7 million people across 215 countries and had caused over 316,000 deaths.
Current measures to treat infected patients and control the spread of the virus have placed a huge burden on healthcare systems and economies around the world. An effective COVID-19 vaccine is urgently needed as a long-term solution to controlling the pandemic. There are over 100 candidate vaccines in rapid development, and around eight of these have started clinical trials in humans. A research team in China recently reported initial results from the first human trial of a potential COVID-19 vaccine in The Lancet.
First human trial of COVID-19 vaccine shows it produces an immune response
Researchers from the Beijing Institute of Biotechnology developed a COVID-19 vaccine using a weakened common cold virus (adenovirus) engineered to carry genetic material coding for parts of the SARS-CoV-2 virus. Known as the Ad5 vectored COVID-19 (Ad5-nCoV) vaccine, it can infect human cells, but is incapable of causing disease. The vaccine is designed to stimulate the body’s immune system to fight off the SARS-CoV-2 virus.
This initial clinical trial in humans, conducted in Wuhan, China, assessed the Ad5-nCoV vaccine’s safety and ability to generate an immune response at different doses. A total of 108 healthy adult volunteers, aged between 18 and 60 years, were randomly allocated to receive low, medium or high doses of the vaccine. Following injection of the vaccine, the researchers tested participants’ blood at regular intervals to measure specific antibodies and specific T cells (a group of immune cells that fight infections) to the SARS-CoV-2 virus. They also monitored any side effects of the vaccine.
The vaccine was well-tolerated at all three doses, with no serious side effects noted within 28 days of vaccination. The most common side effects were mild pain at the injection site, fever, fatigue and headache, all of which resolved.
Within two weeks of vaccination, all dose levels triggered some immune response in the form of binding antibodies (that can bind to the virus but may not attack it) or neutralizing antibodies for SARS-CoV-2. By 28 days, most participants had a four-fold increase in binding antibodies for SARS-CoV-2. Half of the low- and medium-dose participants and three-quarters of the high-dose participants had neutralizing antibodies against SARS-CoV-2. The Ad5-nCoV vaccine also stimulated a rapid T cell response in the majority of volunteers, greater in the middle and high dose groups, peaking at 14 days after vaccination.
Larger trial of the Ad5-nCoV vaccine underway
The researchers are encouraged by these initial findings. A larger, placebo-controlled clinical trial of the Ad5-nCoV vaccine in 500 volunteers is now underway in Wuhan. The new trial aims to determine if the initial trial results can be replicated and if there are any adverse events up to six months after vaccination. It will also include some participants over the age of 60 years, an important target population for the vaccine.
However, Professor Wei Chen (Beijing Institute of Biotechnology), one of the lead researchers, added a note of caution, “The challenges in the development of a COVID-19 vaccine are unprecedented, and the ability to trigger these immune responses does not necessarily indicate that the vaccine will protect humans from COVID-19. This result shows a promising vision for the development of COVID-19 vaccines, but we are still a long way from this vaccine being available to all.”
Written by Julie McShane, MA MB BS
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1. Zhu FC, Li YH, Guan XH, et al. Safety, tolerability, and immunogenicity of a recombinant adenovirus type-5 vectored COVID-19 vaccine: a dose-escalation, open-label, non-randomized, first-in-human trial. The Lancet, Published online: May 22, 2020. https://doi.org/10.1016/S0140-6736(20)31208-3.
2. The Lancet, News release, May 22, 2020. “The Lancet: First human trial of COVID-19 vaccine finds it is safe and induces rapid immune response.” https://www.eurekalert.org/pub_releases/2020-05/tl-tlf052220.php
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