Understanding How COVID-19 Vaccines Work Show
What You Need to Know
How COVID-19 Vaccines WorkCOVID-19 vaccines help our bodies develop immunity to the virus that causes COVID-19 without us having to get the illness. Different types of vaccines work in different ways to offer protection. But with all types of vaccines, the body is left with a supply of “memory” T-lymphocytes as well as B-lymphocytes that will remember how to fight that virus in the future. It typically takes a few weeks after vaccination for the body to produce T-lymphocytes and B-lymphocytes. Therefore, it is possible that a person could be infected with the virus that causes COVID-19 just before or just after vaccination and then get sick because the vaccine did not have enough time to provide protection. Sometimes after vaccination, the process of building immunity can cause symptoms, such as fever. These symptoms are normal signs the body is building immunity. Types of Vaccines: mRNA, Viral Vector, and Protein SubunitFacts about COVID-19 Vaccines Currently, there are three main types of COVID-19 vaccines that are approved or authorized for use in the United States: mRNA, viral vector, and protein subunit. Each type of vaccine prompts our bodies to recognize and help protect us from the virus that causes COVID-19. None of these vaccines can give you COVID-19.
They do not affect or interact with our DNA.
mRNA vaccines (Pfizer-BioNTech or Moderna)To trigger an immune response, many vaccines put a weakened or inactivated germ into our bodies. Not mRNA vaccines. Instead, mRNA vaccines use mRNA created in a laboratory to teach our cells how to make a protein—or even just a piece of a protein—that triggers an immune response inside our bodies. This immune response, which produces antibodies, is what helps protect us from getting sick from that germ in the future. About Pfizer-BioNTech and Moderna Research for mRNA technologyResearchers have been studying and working with mRNA vaccines for decades.
Protein subunit vaccines (Novavax)Protein subunit vaccines contain pieces (proteins) of the virus that causes COVID-19. These virus pieces are the spike protein. The vaccine also contains another ingredient called an adjuvant that helps the immune system respond to that spike protein in the future. Once the immune system knows how to respond to the spike protein, the immune system will be able to respond quickly to the actual virus spike protein and protect you against COVID-19. About Novavax Research for protein subunit technologyProtein subunit vaccines have been used for years.
FACTSHEET How Protein Subunit COVID-19 Vaccines WorkPDF infographic explaining how Protein Subunit COVID-19 vaccines work.
Viral vector vaccines (Johnson & Johnson’s Janssen)Viral vector COVID-19 vaccines use a modified version of a different virus (a vector virus) to deliver important instructions to our cells. About Johnson & Johnson's Janssen Research for viral vector technologyFor decades, hundreds of scientific studies of viral vector vaccines have been done and published around the world.
Developing COVID-19 VaccinesWhile COVID-19 vaccines were developed rapidly, all steps have been taken to ensure their safety and effectiveness. Bringing a new vaccine to the public involves many steps including:
As vaccines are distributed outside of clinical trials, monitoring systems are used to make sure that COVID-19 vaccines are safe. New vaccines are first developed in laboratories. Scientists have been working for many years to develop vaccines against coronaviruses, such as those that cause severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). SARS-CoV-2, the virus that causes COVID-19, is related to these other coronaviruses. The knowledge that was gained through past research on coronavirus vaccines helped speed up the initial development of the current COVID-19 vaccines. After initial laboratory development, vaccines go through three phases of clinical trials to make sure they are safe and effective. No trial phases have been skipped. The clinical trials for COVID-19 vaccines have involved tens of thousands of volunteers of different ages, races, and ethnicities. Clinical trials for vaccines compare outcomes (such as how many people get sick) between people who are vaccinated and people who are not. Results from these trials have shown that COVID-19 vaccines are safe and effective, especially against severe illness, hospitalization, and death. Before vaccines are made available to people in real-world settings, FDA assesses the findings from clinical trials. Initially, they determined that COVID-19 vaccines met FDA’s safety and effectiveness standards and granted those vaccines Emergency Use Authorizations (EUAs). The EUAs allowed the vaccines to be quickly distributed for use while maintaining the same high safety standards required for all vaccines. Learn more in this video about EUAs. FDA has granted full approval for some COVID-19 vaccines. Before granting approval, FDA reviewed evidence that built on the data and information submitted to support the EUA. This included:
These vaccines were found to meet the high standards for safety, effectiveness, and manufacturing quality FDA requires of an approved product. Learn more about the process for FDA approval. Hundreds of millions of people in the United States have received COVID-19 vaccines under the most intense safety monitoring in U.S. history. Several monitoring systems continue to track outcomes from COVID-19 vaccines to ensure their safety. Some people have no side effects. Many people have reported common side effects after COVID-19 vaccination, like pain or swelling at the injection site, a headache, chills, or fever. These reactions are common and are normal signs that your body is building protection. Reports of serious adverse events after vaccination are rare. CDC and FDA continue to closely monitor several reporting systems, like the
CDC provides timely updates on selected serious adverse events reported after COVID-19 vaccination. Learn About Getting Your Vaccine
Getting Your COVID-19 Vaccine ResourcesWhich of the following best explains the main cause of the Great Depression of the 1930s?Which of the following best explains the main cause of the Great Depression of the 1930s? Episodes of credit and market instability undermined the financial system.
Which of the following best describes the historical situation in the 1960s that prompted?Which of the following best describes the historic situation in the 1960s that prompted the emergence of social and political reform movements such as the Black Panther Party? The United States became increasingly divided as conflicts within and between liberal and conservative movements intensified.
Which of the following describes a difference between the arguments made by Chief Joseph?Which of the following describes a difference between the arguments made by Chief Joseph and Commissioner Parker in the excerpts? Chief Joseph believed that Native American tribes had a right to sovereignty, while Commissioner Parker believed that Native American tribes were not sovereign nations.
Which of the following developments best explains changes in agricultural production?Which of the following developments best explains changes in agricultural production in the United States during the 1880s and 1890s? New systems of transportation integrated farming into national markets.
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