HomeLifestyleHealth & FitnessCanSino's single-dose vaccine Convidecia is 91.7% effective against severe COVID-19: Lancet reviewed

CanSino’s single-dose vaccine Convidecia is 91.7% effective against severe COVID-19: Lancet reviewed

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Phase 3 trial results show 57% efficacy against infection and 91% efficacy against severe disease for the Ad5-nCoV COVID-19 vaccine, marketed as Convidecia

  • No vaccine-related serious adverse events were reported, and most adverse events, including injection-site pain, headache, drowsiness, and generalized muscle aches, were mild to moderate.
  • Research is ongoing to determine the vaccine’s long-term safety and effectiveness as well as its effectiveness against delta, omicron and other variants of concern. Additional research into the potential need for a booster dose is also underway. 

According to a phase 3 randomised controlled trial published in The Lancet, one dose of Ad5-nCoV (Convidecia), a COVID-19 vaccine produced in China, is 57.5% effective against symptomatic COVID-19 and 91.7% effective against severe COVID-19 disease beginning 28 days after immunization.

Ad5-nCoV is safe, according to the paper, with no major vaccination-related adverse events or deaths reported among trial participants, and the vaccine elicits a strong antibody response.

Ad5-nCoV is a single-dose viral vector vaccine developed by CanSino Biologics, Inc. and the Beijing Institute of Biotechnology that can be refrigerated between 2°C and 8°C. In several countries, including Argentina, Chile, Mexico, and Pakistan, the vaccine has been certified for emergency use. In Russia, which was also a participant in this clinical trial, a regulatory evaluation is currently underway.

“Our study suggests that one dose of Ad5-nCoV is highly effective against severe disease— potentially helping to ease the tremendous strain COVID-19 has put on health systems around the world by keeping people from becoming seriously ill or requiring hospitalisation. In addition, because the vaccine is effective against severe disease after one injection, it could help provide improved access to vaccination, especially in low- and middle-income countries, where it can be more challenging to reach people with a two-dose primary vaccination course,” said study lead author Dr Scott Halperin, Dalhousie University, Canada.

The trial began on September 22, 2020, and by January 15, 2021, it had enrolled 36,982 participants aged 18 and above, of whom 36,727 had been randomized to receive either a vaccine or a placebo injection across 66 enrolment sites at study centers in Argentina, Chile, Mexico, Pakistan, and Russia.

On January 15, 2021, when the protocol threshold of 150 laboratory-confirmed (RT-PCR positive) symptomatic COVID-19 at 28 days post-injection was met, the researchers conducted an efficacy analysis, with 21,250 trial participants in the primary efficacy cohort. Researchers found 105 positive COVID-19 cases out of 10,590 placebo participants and 45 positive COVID-19 cases out of 10,660 vaccine participants, resulting in a 57.5 % efficacy at 28 days postvaccination.

At 28 days after vaccination, efficacy against the severe disease was 91.7 %, with severe disease defined as a minimum of one of the following clinical symptoms at rest: respiratory failure, evidence of shock, major acute renal, hepatic, or neurologic impairment, or admission to an ICU. COVID-19-related deaths were not reported among vaccination recipients.

Phase 1 and 2 studies showed that Ad5-nCoV was well tolerated and produced enough antibodies that could fight off the virus and neutralize it.

It is important to note that most of the adverse effects were low to moderate in severity and occurred within 7 days of injection. Thrombosis or thrombocytopenia were not reported in any of the research participants.

The authors point out that the efficacy research was done on samples obtained on or before January 15, 2021, therefore it doesn’t cover more recent variants of concern like the delta and omicron variants.

“More research is needed to determine Ad5-nCoV’s effectiveness and durability over a longer period of time as well as its effectiveness against variants of concern, including omicron, which is rapidly overtaking delta as the dominant strain worldwide,” added Dr Joanne Langley, Dalhousie University, Canada.

Additional secondary outcomes, such as efficacy against asymptomatic infection and efficacy against PCR-negative, seroconversion-positive patients, will be examined, according to the authors.

More research is being done to see how effective a single-dose Ad5-nCoV regimen is compared to a two-dose Ad5-nCoV regimen.

Additional study limitations are mentioned by the authors. Despite the fact that the study was conducted in five countries, the majority of study participants included in this analysis came from Pakistan (16,950 participants) and Mexico (13,559 participants), owing to the fact that the trial began in Pakistan on September 22, 2020, and Mexico on November 6, 2020. The study excluded people with pre-existing medical issues, pregnant women, and children. Women and people over the age of 65 were also underrepresented. Despite the fact that researchers used active case seeking methods such as weekly phone calls and text messages, signs and symptoms were self-reported (though confirmed through in-person study visits), therefore not all positive cases may have been included. More study is being done to see how long Ad5-nCoV can last and how effective it is against other types of problems.

Source: 10.1016/S0140-6736(21)02753-7

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