WUHAN, China — As the worldwide number of COVID-19 cases reaches five million, the search for a vaccine has taken an important step forward. Researchers say the first human trial of a possible vaccine has been found to be safe and may effectively fight the virus.
Scientists in China say 108 healthy adults were given a dose of adenovirus type 5 vectored COVID-19 (Ad5-nCoV) during the trial. The drug uses a weakened strain of the common cold (adenovirus) to deliver genetic material which codes itself to find the protein in SARS-CoV-2 — the virus that causes COVID-19. These coded cells then head to the lymph nodes where the immune system creates antibodies that can recognize the virus and attack it.
“These results represent an important milestone. The trial demonstrates that a single dose of the new adenovirus type 5 vectored COVID-19 (Ad5-nCoV) vaccine produces virus-specific antibodies and T cells in 14 days,” Professor Wei Chen of the Beijing Institute of Biotechnology said in a statement.
Although Ad5 was found to create a rapid immune response in the body, scientists warn there’s no guarantee the drug will effectively fight the coronavirus.
“These results should be interpreted cautiously… 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,” Chen explained.
The test group of 18-60 year-olds was split into three groups of 36 and given either a small, medium, or large dose of Ad5. Researchers found that none of the patients suffered from serious reactions to the vaccine after four weeks. The most common side-effects included mild pain in the injection area, fever, and fatigue. The symptoms typically lasted for less than two days.
The study, published in The Lancet, found that nearly every patient had more binding antibodies after 28 days. The antibodies, which learned to attach to the coronavirus, had increased by four times in 97 percent of the test group. Among the patients given the large dose of Ad5, 75 percent were found to have antibodies that can neutralize SARS-CoV-2 in their systems.
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Patients also saw their T cell response increase rapidly, with nearly 93 percent seeing a rise in the body’s ability to fight off infections.
Researchers cautioned that Ad5 still has some issues. The biggest problem is that humans could be immune to adenovirus type 5. About half of the trial patients were found to have a pre-existing immunity to the cold virus which may have slowed the progress of the vaccine.
“Our study found that pre-existing Ad5 immunity could slow down the rapid immune responses to SARS-CoV-2 and also lower the peaking level of the responses,” said Professor Feng-Cai Zhu from Jiangsu Provincial Center for Disease Control and Prevention.
The final results of the Ad5 injections will be evaluated after six months. Researchers are hoping the patients will show a continued resistance to the coronavirus.
A second trial involving 500 healthy adults is already underway in Wuhan, the alleged starting point of the worldwide pandemic. This trial will also see how the drug affects patients over the age of 60.