The public relies on the media for accurate information on SARS-CoV-2. Unfortunately, some media pundits discuss vaccines without a true understanding of the terms or science.

They often muddy and further cloud the issues. Understanding just a few terms can help clear up the confusion.

To start, the words vaccination and immunization are used interchangeably. The term vaccination comes from the Latin word “vacca” meaning cow. It refers to practice of infecting people with cowpox to safeguard them from smallpox.

On the other hand, the word immunization refers to the act providing protection. Purist state the better term of the two is immunization as vaccination implies the use of cowpox.

The term immunization further divides into two types: active and passive. Active immunization depends on the immune system recognizing a weakened form of either a germ or some piece of the germ. The immune system then “actively” makes antibodies that provide long-term protection. MMR (measles-mumps-rubella), polio, varicella (shingles and chickenpox), tetanus and the like are some examples of active immunizations. More than a hundred active immunizations (or you can call them vaccines) are under development for SARS-CoV-2.

People are much less familiar with passive immunization. This is where a person receives antibodies from another source to help prevent an infectious disease. The antibodies provide protection for a couple weeks or months.

Passive immunization is used when time is of the essence as it takes a minimum of two weeks for the immune system to produce protective antibodies.

For example, physicians passively immunize people bitten by a rabid animal by injecting antibodies against the rabies virus. These antibodies provide immediate but short-term protection. Furthermore, the bitten person is actively immunized via a series of four rabies shots given over a span of two weeks to provide lasting protection against any remaining virus.

Additionally, passive immunization can shield those with weak immune systems. It can even provide protection in cases where a vaccine does not exist. Antibodies can be collected from blood donated by several people who may have had the disease (pooled plasma) or from a single person known to have recovered from the illness (convalescent serum).

Antibodies can also be manufactured in a complex process. First, scientists find and clone a white cell from a blood sample that produces a protective antibody. Large batches of the clone are grown to produce great quantities of that antibody (also known as, “monoclonal antibody”).

In the case of SARS-CoV-2, passive immunization may be investigated in the future to protect people at high risk of exposure, such as health care professionals or family members when someone in their household comes down with SARS-CoV-2. Another possibility is to inject people at high risk, such as the elderly, on a regular basis to provide long-term protection.

It doesn’t matter whether you use the term vaccination or active immunization. They are interchangeable. It’s important to understand the roles that active and passive immunization can play protecting us from SARS-CoV-2.

Vaccine Smarts is written by Sealy Institute for Vaccine Sciences faculty members Drs. Megan Berman, an associate professor of internal medicine, and Richard Rupp, a professor of pediatrics at the University of Texas Medical Branch. For questions about vaccines, email

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