A Vaccine is a tiny weakened non-dangerous fragment of the organism and includes parts of the antigen, it's enough that our body can learn to build the specific antibody. Then if the body encounters the real antigen later, as part of the real organism, it already know how to defeat it.
Vaccines have been in use for decades, with millions of people receiving them safely every year. As with all medicines, every vaccine must go through extensive and rigorous testing to ensure it is safe before it can be introduced in a country’s vaccine program.
Each vaccine under development must first undergo screenings and evaluations to determine which antigen should be used to invoke an immune response. This preclinical phase is done without testing on humans. An experimental vaccine is first tested in animals to evaluate its safety and potential to prevent disease. If the vaccine triggers an immune response, it is then tested in human clinical trials in three phases before it is approved safe to use.
All viruses including SARS-CoV-2, the virus that causes COVID-19 will evolve over time. When a virus replicates or makes copies of itself, it sometimes changes a little bit, which is normal for a virus. These changes are called “mutations”. A virus with one or more new mutations is referred to as a “variant” of the original virus.
When a virus is widely circulating in a population and causing many infections, the likelihood of the virus mutating increases. The more opportunities a virus has to spread, the more it replicates and the more opportunities it has to undergo changes
The COVID-19 vaccines that are currently in development or have been approved are expected to provide at least some protection against new virus variants because these vaccines elicit a broad immune response involving a range of antibodies and cells. Therefore, changes or mutations in the virus should not make vaccines completely ineffective. In the event that any of these vaccines prove to be less effective against one or more variants, it will be possible to change the composition of the vaccines to protect against these variants.
Vaccines are a critical tool in the battle against COVID-19, and there are clear public health and lifesaving benefits to using the tools we already have. We must not put off getting vaccinated because of our concerns about new variants, and we must proceed with vaccination even if the vaccines may be somewhat less effective against some of the COVID-19 virus variants. We need to use the tools we have in hand even while we continue to improve those tools. We are all safe only if everyone is safe.