COVID-19 vaccine is safe and triggers immune response in human trial

COVID-19 vaccine is safe and triggers immune response in human trial

Written by Dibash Kumar Das, Ph.D. on July 23, 2020 — Fact checked by Jessica Beake, Ph.D.

According to a new study, a Chinese phase II clinical trial of a COVID-19 vaccine candidate has shown that it is safe and induces an immune response.

Share on PinterestThe results of a phase II clinical trial show that a new COVID-19 vaccine is safe and able to trigger an immune response.

With over 15 million confirmed cases of the new coronavirus, SARS-CoV-2, and more than 624,000 COVID-19 deaths globally, scientists around the world are competing against time to fast-track the development of new treatments to combat the disease.

Globally, scientists are developing about 250 candidate vaccines against SARS-CoV-2 infection. Of these, to date, at least 17 are under evaluation in clinical trials.

Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus hub for more advice on prevention and treatment.

Vaccine development

The authors of the recent study aimed to evaluate the safety and efficacy of a vaccine candidate called adenovirus type-5-vectored COVID-19 vaccine (Ad5-vectored COVID-19 vaccine).

They also wanted to determine the most appropriate dose for a phase III trial in the coming months. They published their results in The Lancet.

The Beijing Institute of Biotechnology in Beijing, China, and CanSino Biologics developed the Ad5-vectored COVID-19 vaccine. It uses a weakened human common cold virus (adenovirus) that produces an immune system response, including antibodies, to fight off the coronavirus.

Danny Altmann, Professor of Immunology at Imperial College London in the United Kingdom, who was not involved in the study, told the Science Media Centre in London:

“The Beijing approach is based on the backbone of a conventional human, common cold virus to which some people have preexisting antibodies, and they, therefore, make a lower response in some people to the vaccine because people have preexisting antibodies to their vector, so may clear it before it has a chance to work properly.”

For the randomized controlled study, which took place in Wuhan, China, the researchers recruited and screened participants for eligibility in April 2020. In total, 508 participants (50% male) were eligible. The average age of the participants was 39.7, with 61% of them aged 18–44, 26% aged 45–54, and 13% aged 55 or older.

Of the 508 participants, 253 received a high dose of the vaccine, 129 received a low dose, and 126 received a placebo. The researchers observed the participants for 30 minutes after the injection to check for immediate adverse reactions and then followed them for any injection site or systemic adverse reactions within 14 and 28 days of the injection.

Additionally, the scientists took blood samples immediately before the treatment and at days 14 and 28 afterward to measure antibody responses.


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