20 December 2020 Author: Luís França, Hospital Beatriz Ângelo COVID-19 pandemic has changed our life. And while we adapt, preventing as we can to get infected, the medical and scientific community has developed several vaccines against the SARS-CoV-2 virus in an unusually short period. All vaccines that will be approved in 2020 and 2021 have been and will continue to be studied over the next few years, both in their efficacy and safety, and these results will be analyzed by the scientific community and by regulatory entities worldwide, including the European Medicines Agency. Therefore, we must look to vaccination with confidence and as a unique opportunity to resume our normal lives. However, we will have to be patient. Vaccine availability during 2021 will still be limited. For this reason, a vaccination plan against COVID-19 was created, which will allow the greatest number of people to be vaccinated in the shortest possible time, taking into account the individual risk of each person and the availability of vaccines. Vaccines against COVID-19 The various vaccines that are expected to be used in the 2021 and 2022 have different characteristics and use different technologies. Results of the phase 3 trials (studies that evaluate efficacy and safety using a very high number of volunteers) of the Pfizer / BioNTech vaccine, the first that is expected to be available, and the Oxford / Astra Zeneca vaccine, have already been published. In addition to these vaccines, other are in an advanced stages of development, such as the Moderna vaccine, and it is possible that the results of the trials will be published very soon. Pfizer/BioNTech vaccine How it works (mechanism of action) The Pfizer / BioNTech vaccine, known as BNT126b2, uses a recent technology with messenger RNA (ribonucleic acid), or mRNA, a molecule that all living beings use as a kind of "recipe" to manufacture a certain protein. The mRNA in this vaccine encodes a protein from the virus that is essential for it to infect cells. When the vaccine is administered to the arm muscle, the mRNA enters the cells of our body, without interfering with our genetic material, and these cells begin to produce the protein and place it outside its cell membrane. The immune system recognizes the protein as foreign and develops the immune response, producing antibodies against the protein and activating defense cells of different types. When after a few weeks the second dose is administered, the immune system strengthens its ability to defend against the virus. After being vaccinated, when someone contacts (is exposed) with the SARS-CoV-2 virus, their immune system is already prepared to recognize the protein and immediately triggers a immune response that destroys the virus before it can infect other cells of the organism. The technology used in the Pfizer / BioNTech vaccine is new, but it is known for other viruses and has been studied for more than 10 years. Effectiveness and safety of the Pfizer / BioNTech mRNA vaccine The phase 3 clinical study that assessed the efficacy and safety of the BNT126b2 included approximately 45,000 people aged 16 to 89 years, of whom nearly half were vaccinated with two doses of the vaccine. The remainder received a placebo, that is, a product with no effect. It was found that the vaccine has an efficacy of about 95% and a good safety profile. The vaccine efficacy is independent of age, sex, race, ethnicity, body mass index or previous diseases. In the group of vaccinated people, there were 8 cases of COVID-19; In the group of placebo, there were 162 cases of COVID-19. As for safety, the most frequent adverse effects were typical of a vaccine and resolved in less than 7 days. Injection site pain was less frequent in individuals over 55 years old (71% after the 1 st dose and 66% after the 2 nd dose) than in individuals aged 16-55 years (83% after the 1 st dose and 78% after the 2 nd dose). Only 1% of participants reported severe pain at the injection site. Systemic adverse effects were more frequent in individuals aged 16-55 years. The most common were fatigue (51% after the 1 st dose and 59% after the 2 nd dose) and headache (39% after the 1 st dose and 52% after the 2 nd dose). Other less frequent and reported systemic side effects were muscle pain, joint pain, diarrhea, fever and chills. All adverse effects will continue to be studied for two years. Oxford/Astra Zeneca vaccine Final remarks Of the various SARS-CoV-2 vaccines currently in development or use, data for two of them are published. Based on the results of clinical trials, the use of the Pfizer / BioNTech vaccine has been approved by the European Medicines Agency and this will be the first vaccine to be used. Considering the vaccine efficacy and safety profile, as well as the requirements of regulatory authorities, I am sure that when my turn to be vaccinated arrives, I will have no fear of doing so. Information about the benefits and risks of vaccination is on current agenda. In case of doubt, always consult your doctor, pharmacist or nurse and use information from credible sources and health institutions. References Polack FP, Thomas SJ, Kitchin N, Absalon J, Gurtman A, Lockhart S, et al. S afety and efficacy of the BNT162b2 mRNA Covid-19 Vaccine . N Engl J Med 2020:NEJMoa2034577. Voysey M, Clemens SAC, Madhi SA, Weckx LY, Folegatti PM, Aley PK, et al. Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK . Lancet 2020:S0140-6736(20)32661-1. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
