Please refer to https://www.cdc.gov/coronavirus/2019-ncov/vaccines/faq.html for more information.
Should I wait for a specific vaccine brand?
You should get any COVID-19 vaccine that is available to you. Do not wait for a specific brand. All currently authorized and recommended COVID-19 vaccines are safe and effective, and CDC does not recommend one vaccine over another.
How do mRNA vaccines work?
According to the Centers for Disease Control and Prevention (CDC), "mRNA vaccines have strands of genetic material called mRNA inside a special coating. That coating protects the mRNA from enzymes in the body that would otherwise break it down. It also helps the mRNA enter the dendritic cells and macrophages in the lymph node cells near the vaccination site. mRNA can most easily be described as instructions for the cell on how to make a piece of the “spike protein” that is unique to SARS-CoV-2. Since only part of the protein is made, it does not do any harm to the vaccinated person, but it is antigenic. After the piece of the spike protein is made, the cell breaks down the mRNA strand and disposes of it using enzymes in the cell. The mRNA strand never enters the cell’s nucleus or affects genetic material. Once displayed on the cell surface, the spike protein causes the immune system to begin producing antibodies which mean the immune system is primed to protect against future infection." Learn more at https://www.cdc.gov/vaccines/covid-19/hcp/mrna-vaccine-basics.html.
How do viral vaccines work?
"Many vaccines use a weakened or inactivated form of the target pathogen to trigger an immune response. Viral vector vaccines use a different virus as a vector instead, which delivers important instructions (in the form of a gene) to our cells. For COVID-19 vaccines, a modified virus delivers a gene that instructs our cells to make a SARS-CoV-2 antigen called the spike protein. This antigen triggers the production of antibodies and a resulting immune response. The virus used in a viral vector vaccine poses no threat of causing illness in humans because it has been modified or, in some cases, because the type of virus used as the vector cannot cause disease in humans." Learn more at https://www.cdc.gov/vaccines/covid-19/info-by-product/janssen/janssen-faqs.html.