NEW DELHI: Nearly three weeks after Russia registered Sputnik V, the world's first Covid-19 vaccine, results from its early-stage clinical trials have been published in 'The Lancet' which show that formulations of a two-part vaccine have a good safety profile with no serious adverse events detected over 42 days.
The trials also confirmed that the vaccine induces antibody responses in all participants within 21 days.
The success of Sputnik V, which is set to enter into a late-stage trial involving 40,000 individuals and ould also be given to high-risk and consenting individuals beginning October, could have implications for India.
Russian government is in talks with India to get the vaccine tried here as part of phase 3 trial and also get Indian manufacturers to mass-produce the vaccine.
Russia had drawn flak internationally for registering the vaccine based on a low powered study whose details were not published for evaluation by the scientific community.
The trial results, meanwhile, show that secondary outcomes or planned outcome measures that are not as important as the primary outcome measure but are still of interest in evaluating the effect of an intervention, the vaccines also produce a T cell response within 28 days.
The new paper reports the findings from two small phase 1 and 2 trials lasting 42 days – one studying a frozen formulation of the vaccine, and another involving a lyophilised (freeze-dried) formulation of the vaccine.
The frozen formulation is envisaged for large-scale use using existing global supply chains for vaccines, while the freeze-dried formulation was developed for hard-to-reach regions as it is more stable and can be stored at 2-8 degrees centigrade.
The two-part vaccine includes two adenovirus vectors –which have been modified to express the SARS-CoV-2 spike protein. The adenoviruses are also weakened so that they cannot replicate in human cells and cannot cause disease (adenovirus usually causes the common cold).
Explaining why they are using two different adenovirus vectors, lead author Dr Denis Logunov, N F Gamaleya National Research Centre for Epidemiology and Microbiology, Russia, said that two different adenovirus vectors have been used in a bid to avoid the immune system becoming immune to the vector.”
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These trials on 76 individuals took place in two hospitals in Russia. The trials were open-label and non-randomized, meaning that participants knew that they were receiving the vaccine and were not assigned by chance to different treatment groups.
The trials involved healthy adults aged 18-60 years, who self-isolated as soon as they were registered for the trial and remained in the hospital for the first 28 days of the trial (from when they were first vaccinated).
The authors have however noted some limitations to their study, including that it had a short follow-up (42 days), it was a small study, some parts of the phase 1 trials included only male volunteers, and there was no placebo or control vaccine.
In addition, they said that despite planning to recruit healthy volunteers aged 18–60 years, in general, their study included fairly young volunteers (in their 20s and 30s, on average).
The researchers also said that more research is needed to evaluate the vaccine in different populations, including older age groups, individuals with underlying medical conditions, and people in at-risk groups.