Results of the First Human Clinical Trial of a VACCINE Developed against the Novel Coronavirus Published

COVID-19 disease caused by the novel coronavirus called SARS-CoV-2 has become a pandemic, and vaccination is presented as the most effective way to control this outbreak. More than 100 "preventive" vaccines against SARS-CoV-2 are under development worldwide. Some have moved into human trials (clinical studies). On 22 May 2020, the respected medical journal Lancet published the results of the first phase-I clinical trial of a modern genetic vaccine developed against SARS-CoV-2. The study, involving 108 healthy people, found that the vaccine successfully induced antibodies against the virus in humans.

The Ad5 vector COVID19 vaccine, tested in humans, is the first vaccine with published trial results. This vaccine uses a weakened cold virus (an adenovirus that readily infects human cells but cannot cause disease) to deliver genetic material encoding the SARS-CoV-2 spike protein into cells. These cells then produce the spike protein and travel to lymph nodes. Here, the immune system recognizes the spike proteins and produces antibodies to fight the coronavirus (see the infographic at the end of the article for how the vaccine works).

The clinical trial examined the safety of different doses of the vaccine and whether they generated an immune response in 108 healthy adults. Participants received a single intramuscular dose at low, medium or high levels. Their blood samples were examined at set intervals, and immune system activity was assessed.

According to the Coronavirus Vaccine Phase-I Clinical Trial Results:

• Within 14 days, a single dose of the novel adenovirus type 5 vector COVID-19 (Ad5-nCoV) vaccine was shown to induce antibodies against SARS-CoV- 2 and T cell production.
• No side effects were observed during the 28 days after vaccination; 83% (30/36) of those receiving the low and medium doses and 75% (27/36) of those in the high-dose group reported at least one side effect within 7 days of vaccination.
• The most common side effects were mild pain at the injection site in 54 percent, fever in 46 percent, fatigue in 44 percent, headache in 39 percent and muscle pain in 17 percent of participants.
• One person receiving the high dose experienced high fever, fatigue, difficulty breathing and muscle pain. However, these side effects lasted less than 48 hours.
• Within 2 weeks after vaccination, all dose levels elicited an immune response in the form of binding antibodies (which can bind to the coronavirus but do not necessarily attack it). Neutralizing antibodies against SARS-CoV-2 were detected in 44 percent of those receiving the low dose, 50 percent of those receiving the medium dose and 61 percent of those receiving the high dose. After 28 days, a 4-fold increase in binding antibodies was observed in most participants (97% in the low-dose group; 94% in the medium-dose group and 100% in the high-dose group).
• The Ad5-nCoV vaccine generated a rapid T cell response in participants. The T cell response peaked at 14 days. A rapid T cell response at 14 days was observed in 83 percent of low-dose recipients, 97 percent of medium-dose recipients and 97 percent of high-dose recipients.
• Analyses performed 28 days after vaccination reported that most participants had a positive T cell response or detectable virus-specific antibodies. This was observed in 78 percent of low-dose recipients, 92 percent of medium-dose recipients and 100 percent of high-dose recipients.

What Does This Development Mean for Us?

• The phase-I clinical trial results of a vaccine developed against SARS-CoV-2 have been published for the first time. A period of 6 months is needed to obtain detailed results.
• Vaccines capable of inducing both antibody and T cell responses are described as the most ideal vaccines. The Ad5-nCoV2 vaccine successfully induced antibody and T cell responses.
• Analyses showed that 56% of participants had previously developed immunity to adenovirus type 5; in other words, they had previously experienced a cold infection caused by adenovirus. These participants showed lower antibody and immune responses after vaccination. This finding suggests that people with pre-existing immunity to adenovirus type 5 may not show a rapid immune response after vaccination.
• Using different doses in the study will also accelerate the studies, particularly those in phase-II.
• However, the study has several limitations, particularly the small number of participants, short-term analyses and lack of a randomized control group (with randomly recruited subjects). This makes it especially difficult to detect rare side effects.
• It must be emphasized that vaccines can be used in humans only after undergoing very detailed safety testing. Every vaccine developed against SARS-ÇoV-2 undergoes safety and efficacy testing in accordance with previously established guidelines.
• A randomized, double-blind, placebo-controlled phase-II trial of the Ad5 nCOv vaccine has begun in Wuhan, China, with 500 healthy participants. The vaccine's safety at different doses will be studied over 6 months.

The infographic poster below summarizes, first, how we develop immunity against the coronavirus without a vaccine (active immunization), then how we develop immunity through a vaccine (passive immunization), and the methods being tested to develop coronavirus vaccines:

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