COVID-19 Vaccines

Abstract

The epidemic caused by SARS-CoV-2, a new coronavirus, is proved itself to be the most important health problem of the 21st century. The high contagiousness of the virus, its unprecedented negative impact on the health system of countries, and the lack of treatments that can improve the prognosis of the disease to date indicate the importance of developing an effective and reliable vaccine against this disease. In addition, it has been suggested that 60%-70% population immunity (herd immunity) required to end the pandemic can only be achieved with vaccines. Before the COVID-19 pandemic, it took an average of 10-15 years to develop a vaccine. However, with the isolation of the virus from the first cases of viral pneumonia in China and making the entire genome available to researchers, the strategies of developing genetically-based vaccines that can be produced in a shorter time and cheaper than inactive vaccines such as mRNA, viral vector which have been intensively researched in the last one or two decades and their adaptation to SARS-CoV-2 vaccine development has reduced this time to 12-18 months. In addition, an unprecedented financial support and the allocation of manpower for the epidemic, which causes the death of thousands of people per day and causes life to halt both socially and economically, has accelerated the vaccine trials. As of mid-December, there were 214 vaccine development trials in nine different categories of which 52 were in clinical phases; 13 of these were in Phase 3. This review summarizes the history of development, safety and efficacy of the four important vaccines that are in Phase 3 and close to clinical use, and the characteristics of the vaccines. The first of these vaccines is the Pfizer / Biontech vaccine, an mRNA vaccine that received FDA approval for the first time on 11 December 2020. The mRNA vaccine developed by Moderna was the second vaccine that applied for FDA approval. The non-replicating viral vector vaccine developed by AstraZeneca with Oxford University attracts attention especially with its low cost. The agreement between the inactive virus vaccine CoronaVac, developed by Chinese Sinovac with traditional vaccine production technology, and the order of Republic of Turkey Ministry of Health for 50 million doses of vaccine puts this vaccine on the agenda for our country. Phase 4 studies of vaccines that will be put into emergency use in the near future will provide very important real-world data on the efficacy and safety of these vaccines..