Russian vaccine trial shows no adverse events and elicits antibody response

Preliminary results from Russian coronavirus vaccine trials suggest the candidates led to no serious adverse events and also elicit an antibody response.

Russian vaccine trials show no adverse events and provide antibodies

Results from two early-phase non-randomised vaccine trials in a total of 76 people indicate that two formulations of a two-part vaccine have a good safety profile with no serious adverse events detected over 42 days.

The findings, published in the Lancet, also found the candidates induced an antibody response in all participants within 21 days.

Secondary outcomes from the trial suggest the vaccines also produce a T-cell response within 28 days.

The paper reports findings from two small phase 1/2 trials lasting 42 days.

One looked at a frozen formulation of the vaccine, and another involving a lyophilised (freeze-dried) formulation.

It is envisaged that the frozen formulation will be for large-scale use, using existing global supply chains for vaccines.

The freeze-dried formulation was developed for hard-to-reach regions as it is more stable and can be stored at 2-8C, the researchers say.

The two-part vaccine includes two adenovirus vectors which have been modified to express the SARS-CoV-2 spike protein.

These types of vaccines are based on weakened versions of adenoviruses which are a group of viruses that typically infect membranes of the eyes, respiratory tract, urinary tract, intestines and nervous system, and include the common cold.

Lead author Dr Denis Logunov, of the N F Gamaleya National Research Centre for Epidemiology and Microbiology in Russia, said: "When adenovirus vaccines enter people's cells, they deliver the SARS-CoV-2 spike protein genetic code, which causes cells to produce the spike protein.

"This helps teach the immune system to recognise and attack the SARS-CoV-2 virus.

"To form a powerful immune response against SARS-CoV-2, it is important that a booster vaccination is provided."

The trials took place in two hospitals in Russia and were open-label and non-randomised - meaning participants knew they were receiving the vaccine and were not assigned by chance to different treatment groups.

The trials involved healthy adults aged 18-60, who self-isolated as soon as they were registered for the trial and remained in hospital for the first 28 days of the trial.

A frozen vaccine (Gam-Covid-Vac - known as Sputnik V) was trialled in the Burdenko Hospital in Moscow, and involved both civilian and military volunteers.

The freeze-dried vaccine (Gam-Covid-Vac-Lyo) trial took place at Sechenov University in the Russian capital, and all volunteers were civilians.

In phase 1 of each trial, participants received one component of the two-part vaccine on day zero.

In phase 2, which started no earlier than five days after the phase 1 trial, participants received the full two-part vaccine - they were given a prime vaccination with the rAd26-S component on day 0, followed by a booster vaccination with rAd5-S component on day 21.

There were 20 participants each in the frozen and freeze-dried vaccine groups.

In order to compare post-vaccination immunity with natural immunity, the authors obtained convalescent plasma from 4,817 people who had recovered from mild or moderate Covid-19.

According to the study, both vaccine formulations were safe over the 42-day study period and well tolerated.

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