Two COVID-19 Vaccine Trials Got Suspended Within 40 days

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Posted on: 25 December 2020 by chen shanshan

Two COVID-19 Vaccine Trials Got Suspended Within 40 days

The R&D of a COVID-19 vaccine that has received much attention was once again pressed the pause button.

Johnson & Johnson announced on the 12th that the company decided to suspend clinical trials of the COVID-19 vaccine candidate developed by its subsidiary Janssen Pharmaceuticals due to an "unexplainable disease" of a subject.

Johnson & Johnson issued a statement on the same day that the company will suspend all clinical trials of the vaccine, including phase 3 clinical trials initiated at the end of September. Currently, an independent committee and relevant experts are investigating and evaluating the subject's illness. According to the statement, adverse events such as diseases and accidents are possible situations in any clinical research, especially large-scale ones. All clinical studies conducted by Janssen Pharmaceuticals have preset guidelines to ensure that the study can be suspended once an unexpected serious adverse event related to the vaccine or drug under development is discovered, and decisions of whether to restart the research will be published after the investigation is clear. Since many clinical trials are randomized, double-blind controlled trials, it is often not immediately clear whether the subjects received the experimental treatment or a placebo.

The suspended candidateis a recombinant adenovirus vector vaccine, of which the phase 3 clinical trial launched on September 23, and planned to recruit approximately 60,000 adult volunteers in approximately 215 locations in the United States and other parts of the world. It is the fourth COVID-19 vaccine candidate to undergo phase 3 clinical trials in the United States.

On September 8th, a large-scale phase III study of another COVID-19 vaccine developed jointly by AstraZeneca and Oxford University was put on hold because of a suspected adverse reaction from a patient in the UK, who had transverse myelitis. R& D of the vaccine was suspended for about a week in the UK and has resumed. In the United States, however, the project is still on hold.

Preclinical & Clinical Trials

Long and complicated as it is, vaccine R&D is full of uncertainty at each step. The development cycle is often 5 to 10 years. Under special circumstances, in order to block the outbreak of acute infectious diseases as soon as possible, the approval cycle can be greatly shortened by using basically the same technology, the same cultured cells, the same adjuvants, and the same raw materials as the existing vaccines.

The development of vaccines is roughly divided into two steps: preclinical research and clinical research, among which pre-clinical research is a prerequisite.

Antigen Discovery

Look for protective antigens that can produce protective antibodies or induce cellular immunity. In general, inactivated or attenuated viruses are often used as candidate antigens.

Safety Evaluation

The safety studies mainlyverify the long-term toxicity, acute toxicity, local irritation, and allergies of the vaccinein vivo through animal models.

Potency Assessment

If the vaccine candidate can protect the existing model animals from the disease after the viral attack, and there is no antibody-dependent disease enhancement (ADE) effect, it can be a truly effective vaccine candidate.

Regarding the 3 clinical trials of a vaccine candidate, Phase I tested its safety, and Phase II continues to ensure safety, and more importantly, its effectiveness, which mainly tested whether antibodies can be produced, and the quantity, time, and duration of the antibodies. In the third phase, a large number of people are vaccinated to observe whether there is any substantial protective effect in the epidemic area.

Johnson & Johnson did not disclose the recovery time and referring to AstraZeneca's case, recovery may not be as easy as imagined.On September 12, the Oxford University team revealed that the vaccine, jointly developed with AstraZeneca, resumed clinical trials in the UK, only 4 days after the suspension, whileon September 16, according to Reuters, it resumed trials in Brazil and India, which is only 8 days since the suspension was announced on September 8. However, in the United States, trials of AstraZeneca’s vaccine have not been approved to resume by now.

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