Published on : 17/11/2020 – 18:24
Moderna, Pfizer, AstraZeneca … In recent months, several laboratories have been racing to develop the first vaccine against Covid-19. If the results announced in November are encouraging, each candidate vaccine has its specificities – method, dosage, storage … France 24 takes stock.
In the space of a few days, several laboratories have loudly proclaimed the effectiveness of their vaccine against Covid-19. The German-American BioNTech / Pfizer Alliance unsheathed the first by claiming in early November that his product was 90% effective. Two days later, the Russians from the Gamaleïa Institute outbid by announcing a 92% efficiency, followed by the American company Modern with a spectacular figure rising to 94.5%.
In this planetary competition, with enormous financial stakes, each laboratory tries to occupy the media field with its vaccine in order to collect the maximum number of pre-orders. However, it is important to remember that these are currently only partial results of phase 3 trials, involving a small number of volunteers. These data, which were communicated through the press, have yet to be published in detail in a scientific journal. And several questions still remain unanswered: How long is the immunity provided by these vaccines? Is the effectiveness also proven on the most fragile subjects? Should we fear serious side effects?
Among the 48 vaccine candidates identified in November by the World Health Organization (WHO), France 24 was interested in those which are at the most advanced stage, phase 3 – during which the effectiveness of the vaccine is measured on tens of thousands of volunteers spread over several continents. This is the case for candidates from Modern, the German-American alliance BioNTech / Pfizer and the Russian research institute Gamaleïa (called Sputnik V). The European project led by the University of Oxford with the Briton AstraZeneca and that of the Chinese laboratory Sinopharm are also at stage 3, but have not yet delivered their results. The others are still in phase 1 (which aims above all to assess the safety of the product) or in phase 2 (where the question of efficacy is already being explored).
“The results announced by Pfizer and Moderna look extremely interesting”, estimated the geneticist Axel Khan Monday, November 16 on France 24. The laboratories have relied on different methods, some already proven, others unprecedented. Moderna and Pfizer / BioNTech have thus bet on a new technique based on “DNA” or “RNA” vaccines, experimental products using pieces of modified genetic material. Concretely, we inject the messenger RNA molecule, which tells cells what to make. With this method, it is not necessary to cultivate a pathogen in the laboratory, it is the organism that does the work. Consequence: these vaccines are faster to develop. But the serum, wrapped in a protective lipid capsule, must be stored at very low temperature, because the RNA is fragile: -70 ° C for BioNTech, against -20 ° C for Moderna.
Another specificity: two doses are necessary to be effective (three weeks apart at Moderna, four at Pfizer), which will complicate logistics and production.
Other manufacturers (like the Chinese Sinopharm) have preferred to rely on more traditional methods which use a “killed” virus. These are the so-called “inactivated” vaccines, as for polio or influenza, or “attenuated” (for measles or yellow fever). The product is then injected into the body to trigger the immune system, which will produce specific antibodies.
Other vaccines, known as “viral vector” vaccines, are more innovative: we take as a support another virus that we transform and adapt to fight Covid-19. This is the technique chosen by the University of Oxford but also by the Russians, who use adenoviruses (a family of very common viruses).
Once phase 3 of trials is conclusive, and then approval to enter the market, comes the stage of large-scale vaccination. This requires companies to have the ability to produce many doses of vaccine – especially if two are needed for a person to be immune. Moderna has committed to distribute 20 million doses by the end of 2020 in the United States, and between 500 million and 1 billion doses worldwide in 2021. The pre-order book is also well filled for Pfizer / BioNTech, which planned to deliver up to 50 million doses by the end of the year and up to 1.3 billion doses next year.
On the Russian side, the production of a large-scale vaccine seems more complicated. At the beginning of November, Moscow proposed to Paris that “the Russian organizations concerned and the Institut Pasteur” cooperate to be able to quickly deliver a sufficient number of doses. No confirmation has yet been given.
Once the doses have been produced, they must be able to be injected. This is quite a logistical challenge for the laboratories that will have to ship their vaccines. Especially those with developed messenger RNA. Indeed, this type of vaccine needs to be stored at low temperature. The announcement of storage at -80 ° C for the Pfizer / BioNTech product has cooled many countries, even if the French government has for its part already reserved 90 million doses. The Minister of Health, Olivier Véran, has also announced the order for 50 super-freezers to be able to keep them.
For its part, Moderna leaves with an advantage since its vaccine can be stored at -20 ° C for six months in the refrigerator (between 2 ° C and 8 ° C) for 30 days and at room temperature for 12 hours. But the Europeans have not, for now, bought any dose.
The Covid-19 pandemic killed at least 1,328,000 people worldwide as of November 17. More than 55 million cases of infection have been officially diagnosed.