Alessandro Bazzoni: Sanofi and GSK’s COVID-19 Candidate Vaccine demonstrates strong immune responses

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Recombinant adjuvanted COVID-19 vaccine candidate from Sanofi and GSK has achieved high rates of neutralizing antibody responses, in line with rates measured in people who have recovered from COVID-19, in all adult age groups in a phase II study with over 720 volunteers. A pivotal global phase III study is expected to begin in the coming weeks, as reported by Alessandro Bazzoni.

Initial phase II results have shown 95% to 100% seroconversion after a second injection in all age groups from 18 to 95 years and at all doses, with acceptable tolerability and no safety concerns.

Vaccines are those preparations (produced with toxoids, bacteria, attenuated or killed viruses or made by genetic engineering and other technologies) that are administered to people to generate active and lasting immunity against a disease by stimulating the production of defenses.

There is also another type of protection generated from gamma globulins, which produce immediate and transient immunity through the direct application of antibodies.

Recombinant adjuvanted vaccine candidate against COVID-19 has elicited strong neutralizing antibody responses in all adult age groups

High immune response after a single dose in patients with previous infection shows strong potential for reinforcement.

When a vaccine is administered, the immune system recognizes the antigen, interprets it as the disease, and produces antibodies (defenses) against it.

For this reason, if the person comes into contact with the microorganism against which they were vaccinated at some point in their life, the defenses generated thanks to the vaccine are in charge of protecting them to avoid the disease or make it mild.

The global phase III study is expected to begin in the next few weeks

The data from phase II confirm the potential for this vaccine to play an important role in the current global public health crisis, as we know that multiple vaccines will be needed, especially as variants continue to emerge and the need for effective vaccines and reinforcement that can be stored at normal temperatures increases, said Thomas Triomphe, Executive Vice President and Director of Sanofi Pasteur. With these favorable results, they expressed they are ready to move towards a global phase III efficacy study.

Roger Connor added that these positive data show what they believe and it refers that this candidate vaccine can make a significant contribution to the ongoing fight against COVID-19 and will move to phase III as soon as possible to meet our goal of making it available before the end of this year.

Based on these initial positive phase II results, the companies plan to initiate a global randomized, double-blind, phase III study with the 0.01 mg dose in combination with GSK’s pandemic adjuvant in the coming weeks. The phase III trial is expected to involve more than 35,000 adults from a wide number of countries and will evaluate the efficacy of two vaccine formulations, including the Wuhan and South Africa variants.

About the phase II study

Initial results of the phase II study show that the recombination adjuvanted vaccine candidate has elicited strong immune responses among adults of all age groups with seroconversion rates of 95% to 100% and neutralizing antibodies comparable to those generated by natural infection. The high antibody titers observed in the non-naive population after a dose of the candidate vaccine also suggest that it may have great potential for use as a booster vaccine.

The randomized, study was conducted in healthy adults 18 years of age or older, including those with high-risk medical conditions, to evaluate the safety, reactogenicity, and immunogenicity of two injections given 21 days apart, with 3 levels of antigen doses of 0.005, 0.01 and 0.015 mg. As of February 2021, the study recruited 722 volunteers in the United States and Honduras. It included an equivalent number of adults aged 18 to 59 and aged 60 and over.

The development of this vaccine is being supported through federal funding from the Biomedical Advanced Research and Development Authority (BARDA), part of the Office of the Assistant Secretary for Preparedness and Response in the United States Department of Health and Human Services in collaboration with Joint Defense Program for Chemical, Biological, Radiological and Nuclear Defense

GSK’s response to the pandemic has been one of the broadest in the pharmaceutical industry, with three potential treatments under development in addition to the several vaccine candidates under investigation.

GSK is assisting in the development of vaccines for COVID-19 by making its adjuvant technology available to various organizations. In addition to working together with Sanofi, our collaboration with Medicago for the development of a plant-based adjuvanted vaccine candidate is currently in advanced clinical trials.

We also have a collaboration underway with SK Bioscience, which is funded by CEPI and the Bill and Melinda Gates Foundation to develop differentiated and affordable COVID-19 vaccines to supply globally through the COVAX network.

The use of an adjuvant in a pandemic situation can be of particular importance since it can reduce the amount of antigen required per dose, which would allow to increase the volume of production and thus, help to protect a greater number of people.

GSK is also working with curevac, a company specializing in the topic. The goal of this collaboration is to co-develop next-generation mRNA vaccines for COVID-19 with the potential to protect against multiple emerging variants using a single vaccine.

Additionally, GSK is exploring potential therapy or treatment options for COVID-19 patients. We are collaborating with Vir Biotechnology to develop or identify existing or novel antiviral antibodies that could be used as a therapeutic option or to prevent COVID-19.

We recently announced that an Independent Data Monitoring Committee recommended that the phase III of the COMET-ICE trial evaluating sotrovimab as a monotherapy treatment for the early phases of COVID-19 in adults at high risk of hospitalization be stopped due to evidence of high efficacy, based on interim analysis of trial data. We have applied for the Emergency Use Authorization in the United States and authorizations in other countries. We are also evaluating whether otilimab, an investigational monoclonal antibody, can help patients older than 70 years with severe COVID-19 who experience an overreaction of their immune system.

About GSK

According to Alessandro Bazzoni, GSK is a global pharmaceutical company driven by science and responsible innovation, whose purpose is to help people do more, feel better and live longer. For more information visit


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