These vaccines mimic the actions of the bacteria or virus that cause disease. They trigger the body to produce antibodies. A vaccine is different from a traditional drug because it uses an active component to trigger an immune response. It can be made to kill a particular type of bacteria or virus, or it can be inactivated and produce a new generation of antibodies. There are more than 170 different vaccines in development against COVID-19. How are they different from each other? There are more vaccines for COVID-19 than ever before. They're designed to stimulate an immune response to the virus and prevent transmission. There are four main categories of vaccines that are involved in clinical trials. These include whole viruses, polypeptide substitute, nucleic acids, and DNA. Many vaccines use whole viruses to stimulate an immune response. There is also a difference between inactivated and live attenuated vaccines. Live attenuated vaccines can still replicate but require cold storage to avoid causing illness. Subunit vaccines use pieces of a pathogen's protein to trigger an immune response. However, they can also weaken the response. This characteristic could make them less effective. Nucleic acid vaccines rely on the genetic material of both cells and organisms to provide the instructions for making the antigen. Usually, the viral spike protein is used to trigger an immune response. Unlike nucleic acid vaccines, viral vector vaccines deliver their instructions to the cell. Through this process, their cells produce an antigen, which triggers an immune response. For instance, the adenovirus that causes the common cold triggers an immunity response. Several vaccines have been introduced during the COVID-19 pandemic. Some of these include those that use new technology, while others have been approved for use on humans for the first time. Although COVID-19 can cause severe illness, it is far less likely to spread than other infectious diseases. This is especially true for people with weakened immune systems. A candidate vaccine goes through various stages before it can be given for human consumption. These stages include the exploratory science, pre-clinical testing, clinical development, and regulatory approval. Before a vaccine can be tested in humans, it has to be tested to see if it is toxic or works well in people. Human trials are designed to spot potential side effects, which are not the same as short-term reactions. Serious side effects are those that are long-term and potentially dangerous. Two new vaccines developed by Moderna and Pfizer-BioNTech use mRNA technology. These vaccines have numerous advantages, such as their fast development and cheaper production.