Updated: September 4, 2020 10:20:59 pm
The secondary results of the trial suggest that the vaccines also produce a T-cell response within 28 days, the researchers said.
The COVID-19 vaccine, Sputnik V, approved by Russia last month, has been shown to elicit an antibody response without serious adverse events in small human trials, according to preliminary results published in The Lancet on Friday.
Results from early phase non-randomized vaccine trials in a total of 76 people show that two vaccine formulations have a good safety profile detected over 42 days and induce antibody responses in all participants within 21 days.
The secondary results of the trial suggest that the vaccines also produce a T-cell response within 28 days, the researchers said.
The findings are based on two small-phase trials lasting 42 days: one studying a frozen formulation of the vaccine and another involving a lyophilized (lyophilized) formulation of the vaccine, they said.
The frozen formulation is intended for large-scale use in existing global supply chains for vaccines, while the lyophilized formulation was developed for hard-to-reach regions as it is more stable and can be stored at 2-8 degrees Celsius. the researchers said.
The two-part vaccine includes recombinant human adenovirus type 26 (rAd26-S) and recombinant human adenovirus type 5 (rAd5-S), which have been modified to express the spike protein of SARS-CoV-2.
Adenoviruses, which generally cause the common cold, are also weakened so that they cannot replicate in human cells and cannot cause disease, according to the researchers.
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These vaccines aim to stimulate both arms of the immune system, the antibody and T-cell responses, so that they attack the virus as it circulates in the body and also the cells infected by SARS-CoV-2.
“When adenovirus vaccines enter people’s cells, they deliver the genetic code for the SARS-CoV-2 spike protein, which causes cells to produce the spike protein,” said study lead author Denis Logunov. , from the National Research Center of Epidemiology and Microbiology of Gamaleya, Russia.
“This helps teach the immune system to recognize and attack the SARS-CoV-2 virus. To form a powerful immune response against SARS-CoV-2, it is important that a booster vaccine is provided, ”Logunov said.
However, Logunov said, booster vaccines using the same adenovirus vector might not produce an effective response.
He said this is because the immune system can recognize and attack the vector, adding that this would block the vaccine from entering people’s cells and teach the body to recognize and attack SARS-CoV-2.
“For our vaccine, we use two different adenovirus vectors in an attempt to prevent the immune system from becoming immune to the vector,” Logunov added.
The trials were conducted in two Russian hospitals, they were open-label and non-randomized, meaning that the participants knew they were receiving the vaccine and were not randomly assigned to different treatment groups.
The trials involved healthy adults between the ages of 18 and 60, who self-isolated as soon as they were registered and remained in hospital for the first 28 days of the trial after they were first vaccinated.
In phase 1 of each trial, participants received a two-part vaccine component: four groups of nine participants received either the frozen or lyophilized rAd26-S or rAd5-S component.
In phase 2, which began no earlier than five days after the phase 1 trial began, participants received the full two-part vaccine: they received a prime vaccine with the rAd26-S component on day 0, followed by a booster shot with rAd5- Component S on day 21.
There were 20 participants each in the frozen and lyophilized vaccine groups, the Lancet study noted.
To compare post-vaccination immunity to the natural immunity formed by infection with SARS-CoV-2, the authors obtained convalescent plasma from 4,817 people who had recovered from mild or moderate COVID-19, they said.
Both vaccine formulations were safe over the 42-day study period and well tolerated, according to the study.
The most common adverse events were injection site pain, hyperthermia, headache, asthenia (weakness or lack of energy), and muscle and joint pain.
The authors note that these adverse effects are also seen with other vaccines, particularly those based on recombinant viral vectors.
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