The Covid epidemic led to the validation of the first messenger RNA vaccines in France (Pfizer, Moderna). The principle of the RNA vaccine is not to inject the virus so that the body develops antibodies against it but molecules of RNA or DNA of this virus which codes for the formation of a protein. Explanations.
[Mise à jour le 24 janvier 2022 à 13h07] More than 123 million injections of Covid vaccines have taken place in France as of January 7, 2022 according to the National Medicines Agency (ANSM) of which more than 97 million with the Comirnaty vaccine from Pfizer. With the vaccine Moderna’s Spikevax also to messenger RNA, it is the most administered in the country against the coronavirus. The arrival of this new type of vaccine, with messenger RNA, has caused concern and fear oflong term side effects. A French pharmacoepidemiology study conducted by Epi-Lighthouse on 46.5 million adults and published on January 18 reassures about the risk of a serious cardiovascular event (excluding myocarditis and pericarditis) with mRNA vaccines (Comirnaty and Spikevax) in people aged 18 to 74 in France. The authors observed cases ofadults aged 18 to 74, vaccinated or not, admitted to hospital in France between December 27, 2020 (date of availability of the first vaccines against Covid-19) and July 20, 2021 (deadline for data availability at the time of the study) for acute myocardial infarction, ischemic or hemorrhagic stroke, or pulmonary embolism. They conclude that “mRNA vaccines against Covid-19 do not increase the risk of myocardial infarction, stroke or pulmonary embolism in people aged 18 to 74”. On the other hand, the adenovirus vaccines (Vaxzevria from AstraZeneca and Janssen from Johnson&Johnson) appear associated with a “slight” increased risk of heart attack myocardium and embolism pulmonary, within two weeks of injection. According to the authors’ estimates, theincrease would reach around 30% for the risks of pulmonary embolism and acute myocardial infarction during the second week following the first dose of AstraZeneca. For the risk of myocardial infarction following the vaccine Janssen “the estimate is more uncertain due to a low total number of cases”. These results corroborate those of other studies international, in particular in Israel, the United States and the United Kingdom. They have been submitted for publication in an international peer-reviewed journal.
What is the simple definition of a messenger RNA vaccine?
The principle of the RNA vaccine is not to inject the virus so that the body develops antibodies against it but molecules of RNA or DNA from this virus which codes for the formation of a protein (Spike in the context of the coronavirus). “The messenger RNA vaccine is a vaccine that consists of use virus gene which codes for the formation of the surface protein (Spike). The receptive cells which will receive this messenger RNA will make virus protein. This protein will be found on the surface of the cells and the immune cells will consider that the cells provided with these antigens are similar to viruses. These cells have become foreign to our body because they have the S protein on their surface, which is in principle on the surface of the virus. Immune cells destroy these cells that carry the S antigen. This vaccination leads our cells to produce antigen themselves in large quantities.“ explains Dr. Stéphane Gayet, infectious disease specialist and hygienist. A messenger RNA vaccine is “a very recent and particularly innovative vaccine technique performed with molecular biology techniques”. mRNA stands for “messenger (m) ribonucleic acid (RNA)”. Messenger RNA is a molecule that mediates between DNA and the proteins it codes for. “Messenger RNA is the most limited code in the genome.” says Dr. Gayet. These vaccines are also technologically revolutionary. Those are nanovaccines. The specially prepared viral messenger RNA is encapsulated in lipid nanoparticles to be delivered intact inside the recipient cells. “If the RNA came into contact with these cells alone, it would be quickly destroyed because it is perceived as very dangerous by the immune system and would give violent reactions. lipid-based chemical capsules cross cell membrane well and deliver messenger RNA to cells“ explains the infectious disease specialist.
What are the differences with other vaccines?
A classic vaccine is a “antigenic preparation intended to induce the development of specific active immunization” defines Dr. Gayet. This immunization can be obtained by injecting an attenuated viral particle (“live” attenuated vaccines) or inactivated (inactivated vaccines) or part of the viral envelope (envelope protein antigen) in order to cause a first encounter between the main viral antigen and immune cells. The lymphocytes identify the antigen and memorize this information. During the second encounter, the antigen having been memorized, there is a secondary reaction which quickly and effectively fights the antigen and avoids the disease. “Immunization takes time because the antigens must be recognized by the lymphocytes” emphasizes Dr. Gayet. Messenger RNA vaccines are not antigenic preparations. They do not use any directly pathogenic element. “These are genetic vaccines, not made from antigens but from genetic code” inform the infectiologist. “The stage of recognition by the immune system is faster and easier. The immune response is spontaneously sufficient: no need for an immune adjuvant.”
The BioNTech/Pfizer vaccine against Covid must be stored at -80°C.
What is the list of messenger RNA vaccines for Covid?
Two vaccines against Covid based on messenger RNA are administered in France: the vaccine Comirnaty of Pfizer and the vaccine Moderna’s Spikevax. Also allowed are viral vector vaccines from AstraZeneca (Vaxzevria) and Johnson&Johnson (Janssen). After injection, the messenger RNA of these vaccines will produce the viral envelope protein S in the body, which will in turn trigger the immunological reaction and protection against a subsequent infection caused by Sars-Cov-2. . The body will therefore manufacture its own vaccine itself. (in the classic sense of the term) from the injection of part of the genetic code of the virus. These vaccines are easier to produce than conventional vaccines, which partly explains their rapid development. “Conventional vaccines are made up of viral particles or parts of the viral particle. You have to have cells make these viral particles, which takes a very long time, then check that it is the right virus that is produced and that it does not is not dangerous. With the messenger RNA vaccine, there is no longer any need for cell cultures. We know how to make messenger RNA quickly.” explains Dr Stéphane Gayet.
What side effects?
One of the advantages of these vaccines is that they do not need immune adjuvants to be effective, unlike inactivated virus vaccines (like the flu vaccine for example). “It’s always interesting toavoid bringing foreign molecules to our organism” says Dr. Gayet. If you are worried about RNA injection, remember that messenger RNA stays in the body transiently and it cannot integrate into the human genome. “Messenger RNA cannot incorporate into or modify our genes” reassures Dr. Gayet, because of the absence of the enzyme which makes it possible to pass from transcribing RNA into DNA. A French pharmacoepidemiology study conducted by Epi-Lighthouse on 46.5 million adults and published on January 18 reassures about the risk of a serious cardiovascular event (excluding myocarditis and pericarditis) with mRNA vaccines (Comirnaty and Spikevax) in people aged 18 to 74 in France. The authors observed cases ofadults aged 18 to 74, vaccinated or not, admitted to hospital in France between December 27, 2020 (date of availability of the first vaccines against Covid-19) and July 20, 2021 (deadline for data availability at the time of the study) for acute myocardial infarction, ischemic or hemorrhagic stroke, or pulmonary embolism. They conclude that “mRNA vaccines against Covid-19 do not increase the risk of myocardial infarction, stroke or pulmonary embolism in people aged 18 to 74”. On the other hand, the adenovirus vaccines (Vaxzevria from AstraZeneca and Janssen from Johnson&Johnson) appear associated with a “slight” increased risk of heart attack myocardium and embolism pulmonary, within two weeks of injection. According to the authors’ estimates, theincrease would reach around 30% for the risks of pulmonary embolism and acute myocardial infarction during the second week following the first dose of AstraZeneca. For the risk of myocardial infarction following the vaccine Janssen “the estimate is more uncertain due to a low total number of cases”. These results corroborate those of other studies international, in particular in Israel, the United States and the United Kingdom. They have been submitted for publication in an international peer-reviewed journal.
What are the contraindications of RNA vaccines?
A list of contraindications hindering vaccination against covid-19 has been drawn up by the National Agency for the Safety of Medicines (ANSM) and the High Authority for Health (HAS). This list does not make big differences between RNA or viral vector Covid vaccines like AstraZeneca or Janssen. In particular, there is a history of documented allergy (allergist opinion) to one of the components of the vaccine, in particular polyethylene glycols and the risk of cross-allergy to polysorbates; an anaphylactic reaction at least grade 2 (damage to at least 2 organs) to a first injection of a vaccine against COVID posed after allergological expertise; or myocarditis or PIMS in children.
Can RNA vaccines prevent cancer?
RNA vaccines could help fight cancer on the same model as RNA vaccines against viruses. “It’s here immune therapy. The goal is to stimulate the formation of antibodies” indicates the infectiologist. The objective is to induce a specific and lasting immune response against tumor cells with antitumor vaccination approaches based on tumor markers which constitute the target antigens (Ag). The RNA vaccine is one such approach. It would have the advantage of being applicable to all cancers, all cancer cells of the same cancer generally having (monoclonal cancers) the same genome. This involves injecting lipid nanoparticles containing messenger RNA coding for the tumor antigen expressed on the surface of cancer cells. (1)
Thank you to Dr Stéphane Gayet, infectious disease specialist and hygienist.
Sources:
Assessment of the risk of myocardial infarction, stroke and pulmonary embolism following the various anti-COVID-19 vaccines in adults under 75 years of age in France. Jérémie Botton, Marie-Joëlle Jabagi, Marion Bertrand, Bérangère Baricault, Jérôme Drouin, Stéphane Le Vu, Alain Weill, Paddy Farrington, Mahmoud Zureik, Rosemary Dray-Spira. January 18, 2022
The RNA vaccine, a promising approach for reactivating the immune system in the fight against cancer Cancer immunotherapy via systemic RNA delivery to dendritic cells, Med Sci (Paris) 2017; 33: 852–856, Mathieu Richaud and Nathalie Bendriss-Vermare. (1)