First Human Trial Of Possible COVID-19 Vaccine Triggers Rapid Immune Response, Few Side-Effects

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.

Rapid Response

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.

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.

Vaccine Roadblocks

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.

An experimental vaccine against the coronavirus showed encouraging results in very early testing, triggering hoped-for immune responses in eight healthy, middle-aged volunteers, its maker announced May 18.

Study volunteers given either a low or medium dose of the vaccine by Cambridge, Massachusetts-based Moderna Inc. had antibodies similar to those seen in people who have recovered from COVID-19.

In the next phase of the study, led by the U.S. National Institutes of Health, researchers will try to determine which dose is best for a definitive experiment that they aim to start in July.

In all, 45 people have received one or two shots of the vaccine, which was being tested at three different doses. The kind of detailed antibody results needed to assess responses are only available on eight volunteers so far.

The vaccine seems safe, the company said, but much more extensive testing is needed to see if it remains so. A high dose version is being dropped after spurring some short-term side effects.

The results have not been published and are only from the first of three stages of testing that vaccines and drugs normally undergo. U.S. government officials have launched a project called “Operation Warp Speed” to develop a vaccine and hopefully have 300 million doses by January.

Worldwide, about a dozen vaccine candidates are in the first stages of testing or nearing it. Health officials have said that if all goes well, studies of a potential vaccine might wrap up by very late this year or early next year.

More than 4.7 million infections and 315,000 deaths from the coronavirus have been confirmed worldwide since it emerged in China late last year. There are no specific approved treatments, although several are being used on an emergency basis after showing some promise in preliminary testing.