A coronavirus vaccine candidate developed in Russia prompted an immune response and didn’t cause serious adverse reactions in early trials, according to new data released today (Sept. 4).
This data was released weeks after Russia announced that it had approved its vaccine for the general population (but had actually only approved it for a small group of people), Live Science reported, drawing criticism from public health experts who said there was not enough data to prove the vaccine was safe and effective.
Early results from the “Sputnik V” phase 1/phase 2 clinical trials were published today in the journal The Lancet. Between June 18 and Aug. 3, the researchers enrolled 76 healthy participants between 18 and 60 years old to be given the candidate vaccine, developed by the Gamaleya Research Institute of Epidemiology and Microbiology, in one of two Russian hospitals.
The researchers tested two different forms of the vaccine, made from weakened adenoviruses armed with genes that code for the coronavirus’ spike protein — which the virus uses to invade human cells. This type of vaccine is called a vector-based vaccine because it uses a weakened virus (a vector) to deliver genetic information from the pathogen to the body to spur the immune response, according to a Live Science vaccine roundup. Several other candidate vaccines, such as those developed by Johnson & Johnson, the University of Oxford/AstraZeneca, and CanSino Biologics are also made from weakened adenoviruses.
The trial did not include a control group, or a comparison group of people who received a placebo shot instead of the active vaccine, a limitation that the authors noted in the study. A control group is usually a key component of clinical trials to help ensure that the effects seen are solely due to the vaccine itself, and not due to an outside factor.
In total, 18 volunteers received one formulation, another 18 received the other and 40 people received both. “Both vaccine formulations were safe and well tolerated,” the researchers wrote in the paper. The most common side effects were mild: pain at the injection site, an increase in body temperature, headache, asthenia (physical weakness or lack of energy), and muscle and joint pain. These mild effects were similar to those elicited by other adenovirus vaccines and there were no serious adverse effects, the researchers wrote. The participants were monitored for 28 days (and after 42 days for phase 2 participants) and will be followed-up up to 180 days, according to the research.
The vaccine generated an immune response in all participants, prompting the immune systems to produce neutralizing antibodies (molecules that can latch onto the virus and block it from infecting cells) and other immune cells, such as T cells, against the coronavirus.
The researchers noted in the paper that neutralizing antibody levels were lower than those reported for the University of Oxford vaccine and other vaccines, such as Moderna’s based on messenger RNA (mRNA) technology. But the level of neutralizing antibodies was comparable with the amount of neutralizing antibodies that the body develops naturally in patients who recover from COVID-19.
Similar to the studies before it, these results are “encouraging but small,” Naor Bar-Zeev, an associate professor at Johns Hopkins Bloomberg School of Public Health and Dr. Tom Inglesby, the director of the Center for Health Security at the Bloomberg School of Public Health, wrote in an accompanying commentary also published Sept. 4 in The Lancet. “The immunogenicity bodes well, although nothing can be inferred on immunogenicity in older age groups, and clinical efficacy for any COVID-19 vaccine has not yet been shown.”
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In other words, there’s no way to know whether the same immune response would happen in older adults, and we don’t yet know if the vaccine actually prevents infection.
Showing that a COVID-19 vaccine is safe will be “crucial” in order for the public to trust the vaccine and be willing to get it, they wrote. “Safety outcomes up to now are reassuring, but studies to date are too small to address less common or rare serious adverse events,” the researchers wrote.
On Aug. 26, researchers at the Gamaleya Research Institute of Epidemiology and Microbiology received approval to conduct a phase 3 trial, which tests the drug in a large group of people and is the only way to show a vaccine is both safe and effective. The trial is expected to enroll 40,000 people and include a placebo, according to clinicaltrials.gov.
Originally published on Live Science.
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