The results of Phase 1/2 studies of the Sputnik Light vaccine have been published in the prestigious medical journal Lancet. In the article, scientists draw conclusions about the safety, immunogenicity and tolerability of the vaccine in volunteers.
The composition of this vaccine is identical to the first component of the classic “Sputnik V” vaccine. The study was funded by the Russian Direct Investment Fund, which is involved in the promotion of the vaccine. The study was conducted in 110 healthy volunteers aged 18 to 59 years at the Eco-Safety Clinical Center in St. Petersburg.
“The results show that the vaccine was well tolerated and induced both humoral and cellular immune responses in both seronegative (previously antibody negative – BBC) and seropositive (with antibodies) healthy adults,” the article says. Scientists monitored neutralizing antibodies (the most important in fighting virus entry into cells) and the number of participants who experienced adverse events, which were tracked throughout the study.
Cellular immunity and changes in neutralizing antibody levels were also measured. Prior to vaccination, all study participants were tested for antibodies to the coronavirus, and those who tested positive (14 people) were placed in one group and those who had no antibodies (96 people) were placed in another group.
The authors of the article concluded that even a single injection is sufficient for previously antibody-negative volunteers to rapidly mount an immune response. Seroconversion (production of specific antibodies in the blood serum) occurred in 100% of cases by day 42. By day 10, a more pronounced immune response was observed in the group of individuals who had previously had antibodies compared to the group with no detectable antibodies, as well as compared to the group of recovering patients. In those who had not previously had antibodies, there was only a slight increase in titers by this day. At all time points (days 10, 28 and 42), average antibody titers were significantly higher in subjects with prior immunity than in those without, the researchers reported.
This confirms previous conclusions by scientists in many countries that one dose of vaccine is likely to be sufficient for effective maintenance of neutralizing antibody titers (revaccination). For example, previously published studies have shown that a second dose of the Pfizer or “Sputnik V” vaccine does not result in a further increase in antibody titers in those who are already immune, and that only one dose of vaccine is required for effective revaccination. A particularly large increase was observed in the pre-immune group on day 28 after vaccination, but there was no statistically significant increase in neutralizing antibody titers by day 42.
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After testing the neutralization of the “alpha” and “beta” strains, the scientists concluded that it decreased by 1.11 and 1.99 times, respectively, compared to the “wild” strain. “Referring to recently published data using sera from people vaccinated with “Sputnik V”, we expect that vaccination with “Sputnik Light” will still be able to neutralize the B.1.617 variant (from which the “delta” variant originates – BBC), but obviously at a reduced titer,” the article says. The mentioned study concluded that the neutralization of the “delta” variant by sera from those vaccinated with “Sputnik V” decreased by a factor of 2.5.
Cellular immune response formed in 96% of those who had no immunity before vaccination by the 10th day after the injection, scientists write. No significant statistical differences were found between groups for this parameter, as there were few people with previous immunity, but cellular immunity was formed in all of them after a single vaccination.
According to the study, there were no serious adverse events following vaccination of volunteers with Sputnik Light. Moderate side effects were observed in 5.5% of cases. The majority of systemic and local side effects reported were mild – 66.4%.
The scientists write that they found no correlation between the number of neutralizing antibodies and age or pre-existing neutralizing antibodies to the Ad26 adenovirus, which is the “carrier” of the SARS-Cov-2 gene fragment in Sputnik Light. It has been suggested that previous immunity to the adenovirus vector may prevent the formation of antibodies against the vaccine.
“Single-component vaccines against SARS-CoV-2 with simple and easy administration compensate for the shortage of vaccines, allowing population immunity to be achieved in a shorter period of time, thereby contributing to the prevention of new waves of Covid-19 worldwide,” the scientists said.
“Our results show that the ‘Sputnik Light’ vaccine is safe and immunogenic in both seronegative and seropositive healthy adults. Therefore, ‘Sputnik Light’ can be considered not only for primary vaccination, but also as an effective tool for re-vaccination or vaccination after previous Covid-19 infection. These data have prompted us to initiate an international, multicenter, randomized, double-blind, placebo-controlled Phase 3 trial to further evaluate the efficacy of the vaccine,” the article states.
Another study of “Sputnik Light” (or the first component of “Sputnik”), conducted in Argentina, was published on September 12 in the journal EClinicalMedicine (published by Lancet). The vaccine was studied in the age group of 60-79 years. Its effectiveness was estimated at 83.7%. Argentinean scientists found that Sputnik Light prevented 78.6% of laboratory-confirmed SARS-CoV-2 infections, 87.6% of hospitalizations and 84.8% of deaths within 21-83 days of vaccination.