The companies’ intention is to test the vaccine as a booster for previous sera. The drug will be available in the last quarter of 2021.
Sanofi has just announced positive results from its most advanced Covid-19 vaccine. CoV2 preS dTM is its scientific name and the company indicates that it produces a strong immune response in all groups of adults tested, between 18 and 95 years.
The characteristic of this vaccine is that it uses a different technology from those currently approved against Covid-19. If the ones being used in Spain are based on messenger RNA (Pfizer-BioNTech and Moderna) or on adenovirus vectors (AstraZeneca and Janssen), this uses a recombinant protein and a molecule that stimulates the creation of antibodies by the immune system.
Executive Vice President of Sanofi, Thomas Triumph, has indicated that this vaccine has the potential to “play a role in solving the current public health crisis, since we know that multiple vaccines will be necessary, especially as new variants continue to emerge and the need for effective vaccines and increases. of reinforcement, which can be stored at normal temperatures”.
The results of the trial on which this announcement is based have not yet been published, so until they are published, this is what is known so far about the French company’s vaccine, in collaboration with the British laboratory GSK.
What does this vaccine consist of?
Unlike those currently approved, the Sanofi and GSK vaccine uses a different way of generating neutralizing antibodies, which are the ones that attack the virus. If those of Pfizer-BioNTech and Moderna introduce messenger RNA copies of the virus so that human cells generate the SARS-CoV-2 spike protein (which allows it to infect cells), and those of Janssen and AstraZeneca use a adenovirus to introduce its genetic material, this vaccine is based on a different mechanism.
The scientists copied the genetic sequence of the virus’ spike protein and inserted it into a plasmid, a circular DNA molecule found in bacteria that replicates independently. That is why this vaccine is called recombinant, because combines the genetic sequence of the coronavirus with a different one.
The plasmid is introduced into another type of virus, called a baculovirus, which infects cells grown in the laboratory. These cells then begin to use that genetic information of the virus to produce copies of the protein, which are later collected and purified, introducing it into the company’s vials.
What’s more, this vaccine contains an adjuvant, a different component that alerts the immune system and stimulates it to make more antibodies. This adjuvant, known as AS03, is provided by GSK, while the recombinant protein is from Sanofi.
How many doses are given?
The VAT00002 trial, whose preliminary results were announced by both companies on Monday, is based on the administration of two doses of the vaccine 21 days apart. It began on February 24 and will end in April 2022, since the 722 people participating in it will be followed up for a year.
How effective is the vaccine?
Here’s the thing. According to the companies, the vaccine has generated neutralizing antibody responses in between 95 and 100% of those vaccinated with two doses and in all age groups 18 years and older: from young adults to people over 80 years of age. In addition, the response with a single dose in people who had already passed the disease is defined by Sanofi and GSK as “high”.
Efficacy – understood as the percentage of Covid-19 infections that it prevents compared to placebo – will be determined by the phase III trial, starting in a few weeks. This trial has only measured whether the vaccine generates sufficient neutralizing antibodies to presume that efficacy on days 1 and 36 of vaccination (that is, two weeks after receiving the second dose).
In addition, it has done so in a small sample of people (722), excluding vulnerable individuals such as people undergoing anticoagulant treatment, marrow or solid organ transplants, or patients who have received chemotherapy in the last 90 days.
This phase III trial, which will establish the efficacy of this preparation, will recruit 35,000 people from a wide range of countries (the current one has only been carried out in the US and Honduras), which will be administered two doses of 10 micrograms of the vaccine (until now, doses of between 5 and 15 micrograms had been tested) and its adjuvant AS03, or a placebo, spaced 21 days apart.
Is it effective against new variants?
That is another key point that remains to be known. The VAT00002 assay measures the antibody response of the vaccine, but not its efficacy against infections, so it is not known how it works with different variants. The phase III trial aims to evaluate this efficacy in two formulations against the Wuhan (the original) and South African variants.
There is another way to check whether this vaccine holds promise against new variants, and that is submit serum samples from vaccinated patients to virological cultures of the different variants. In fact, this is the strategy that has been followed to determine if the current vaccines work against the new variants, since, in general, the clinical trials proposed were prior to them or in areas where they were not widespread.
When will this vaccine be available?
Sanofi and GSK hope that their serum can be approved in the last quarter of the year, when adult vaccination will be completed in most developed countries (the planned trial does not include children).
Both companies have indicated that their intention is to carry out studies with this vaccine as a booster dose, regardless of the technology of the first vaccine received by the inoculated person, so the company’s strategy seems to be will be based on complementing pending vaccinations