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Tuesday, October 19, 2021

Explained: Reading Russian Covid-19 vaccine trial results

Russia coronavirus (Covid-19) vaccine trial results: What are the results, and how significant are the findings?

Written by Anuradha Mascarenhas | Pune |
Updated: September 7, 2020 8:53:08 am
The vaccine is the first in the world to be authorised for general use. (Photo: AP)

The much-criticised Russian vaccine for novel coronavirus was found to be safe and also triggered a “strong” immune response, according to results of phase-1 and phase-2 clinical trials published in The Lancet.

The vaccine is the first in the world to be authorised for general use. It was approved by the Russian government on August 11, without phase-3 trials, triggering global criticism. Phase-1 and phase-2 trials were completed in less than two months and, it now emerges, were done on only 76 people.

What is the Russian Covid-19 vaccine?

The vaccine, developed by Moscow’s Gamaleya Institute, uses two adenoviruses to inject the genetic material of the novel coronavirus into humans in order to trigger an immune response. Adenoviruses, which cause a range of respiratory diseases in human beings, are used as carriers to deliver several existing drugs and vaccines for other diseases as well, after being stripped of their ability to replicate.

What were the trials for which results have been reported?

The vaccine developers carried out two separate studies, both involving phase-1 and phase-2, at two hospitals in Moscow. The 76 participants included 38 at either location.

Two variants of the vaccine were used, using different adenoviruses. In phase-1 of each study, nine people were injected with one formulation, and nine with the other. In phase-2 of both studies, 20 participants were given shots of both formulations.

Lead author Denis Logunov of Gamaleya Institute explained why two formulations were used. “To form a powerful immune response against SARS-CoV-2, it is important that a booster vaccination is provided. However, booster vaccinations that use the same adenovirus vector might not produce an effective response because the immune system may recognise and attack the vector (carrier). This would block the vaccine from entering people’s cells and teaching the body to recognise and attack SARS-Cov2. For our vaccine, we use two different adenovirus vectors in a bid to avoid the immune system from become immune to the vector,” Logunov said.

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What were the results?

The published findings say “both vaccine formulations were safe and well tolerated”. The participants did complain of some side effects but these were not serious. “The most common adverse events were pain at injection site (58 per cent of participants), hyperthermia (or high temperature in 50 per cent of participants), headache (42 per cent), asthenia (or lack of energy, 28 per cent), and muscle and joint pain (24 per cent). Most adverse events were mild and no serious adverse events were detected,” the study says.

In addition, all participants were found to have produced antibodies to coronavirus, which shows that the vaccine was able to trigger an immune response.

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How significant are these findings?

The results show that the vaccine is at least safe to be used and does not harm the person. However, the relatively small number of volunteers who participated, and the short duration of follow-up (42 days) might not satisfy all the experts.

In the absence of phase-3 trials, questions over the effectiveness of the vaccine remain. In phase-3, a vaccine candidate is tried on several hundred volunteers in real-life situations, outside of laboratory conditions, to assess whether the immune response generated is able to effectively fight the disease. The participants are usually followed for several months to study the impact of the vaccine on their ability to thwart the disease.

Following the criticism, Russia had said it would conduct phase-3 trials as well, and that the August 11 authorisation was only “conditional”. Phase-3 trials are planned to start soon in several countries. The developers had earlier planned to test the vaccine on 2,000 volunteers in phase-3, but later said they would enrol 40,000.

How are other major vaccine candidates progressing?

There are three other leading vaccine candidates, developed by Pfizer, Oxford University in collaboration with AstraZeneca, and Moderna. All three are currently undergoing phase-3 trials.

At least two Chinese vaccines too have been approved without phase-3 trials, and these two also plan to start the final stage trials soon. Besides, close to 30 other vaccine candidates are currently in phase-1 and phase-2 trials.

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