COVID-19 Common Terms

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Anaphylaxis: An acute and potentially life-threatening allergic reaction

Antibodies:  Proteins made by the immune system to fight infections like viruses. They may help to ward off future occurrences by those same infections. Antibodies can take days or weeks to develop in the body following exposure to a COVID-19 infection or vaccination and it is unknown how long they stay in the blood.

Antibody or Serology Test: Looks for antibodies in your blood to determine if you had a past infection of the virus that causes COVID-19.

Asymptomatic: There are no symptoms. You are considered asymptomatic if you:

  • Have recovered from an illness or condition and no longer have symptoms
  • Have an illness or condition (such as COVID-19) but do not have symptoms

Clinical Trial: A type of clinical study that involves research using human volunteers (also called participants) that is intended to add to medical knowledge.

Contact Tracing: Identification, monitoring, and support of a confirmed or probable case's close contacts who have been exposed to, and possibly infected with, the virus. The infected patient's identity is not discussed with contacts, even if asked.

Emergency Use Authorization: A mechanism the FDA can use to facilitate the availability and use of medical countermeasures, including vaccines, during public health emergencies such as the current COVID-19 pandemic.

Herd Immunity: Occurs when enough people have protection, either from a previous infection or vaccination, making it unlikely that a virus or bacteria can continue to spread and cause disease.

Messenger RNA Vaccines: Also called mRNA vaccines, they are a new type of vaccine to protect against infectious diseases. Instead of putting a weakened or inactivated germ into our bodies to trigger an immune response, mRNA COVID-19 vaccines contain lab-made mRNA molecules with specific instructions for cells to create the spike protein found on the surface of the virus. The presence of the spike protein triggers an immune response inside our bodies. That immune response, which produces antibodies, is what protects us from getting infected if the real virus enters our bodies.

Viral Test: A test that checks specimens from your nose or your mouth (saliva) to find out if you are currently infected with a virus like SARS-CoV-2, the virus that causes COVID-19. Two types of viral tests can be used:

  • Nucleic acid amplification tests (NAAT) detect a virus's genetic material and are commonly used in laboratories. NAATs are generally more accurate, but sometimes take longer to process than other test types.
  • Antigen tests detect viral proteins and are generally not as sensitive as NAATs, particularly if the antigen test is used on someone without COVID-19 symptoms. If you have a positive or negative antigen test, your health care provider may need to confirm the test result with a NAAT.

Viral Vector Vaccine: Many vaccines use a weakened or inactivated form of the target pathogen to trigger an immune response. Viral vector vaccines use a benign virus to deliver 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 production of antibodies and a resulting immune response.

Virus Variants: Viruses constantly change through mutation. A variant has one or more mutations that differentiate it from other variants in circulation. As expected, multiple variants of the virus that causes COVID-19 have been documented in the United States and globally throughout this pandemic. To inform local outbreak investigations and understand national trends, scientists compare genetic differences between viruses to identify variants and how they are related to each other.