Francisco R. Velázquez, M.D.: COVID-19 vaccine boosters and additional doses: What does it mean?

The average adult processes roughly eleven thousand liters of air on any given day. The air we breathe typically contains microorganisms, such as bacteria and viruses. Many of those are considered pathogenic, or capable of causing disease. Our immune system, including all the specialized cells in the upper respiratory tract, protects us from the potential invasion. One day’s worth of air contains between a hundred thousand and a million microorganisms. If the natural barriers are penetrated, the immune system is activated. Components of the microorganism are recognized as foreign to the human body. We call these antigens. They are the components that generate the immediate immune response, typically known as antibodies. The process will result in the production of long-term memory cells that remember the offending antigen and will respond with a more specific immune response than the first encounter. That is the process of natural immunity.

Vaccines are biological products that safely induce an immune response, which mimics the response elicited by a microorganism. Vaccines contain specific antigens that either prime the immune system if you have never been exposed or remind the system of a past exposure and what needs to be done to eliminate the microbe. Both the infection-induced and the vaccine-induced responses are natural processes. Thus, it makes sense that to be effective, long-term vaccines may need more than one dose or a “reminder” booster shot.

What’s the difference? In general terms, in order to provide the intended protection, some vaccines need more than one dose. That is true of vaccines for Varicella, Hepatitis A and B, and Human Papilloma Virus (HPV). The Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices recommends that all children 6-months-old through 8-years-old should get two doses of flu vaccine the first year that they are vaccinated against the flu.

The first dose primes the system, and the second one, received about a month later, ensures that there are enough antibodies to protect the child if exposed. Additional doses are also utilized under specific circumstances. In the case of COVID-19 vaccines, a third dose of the m-RNA vaccines was recommended in August for those who are immunocompromised. The ability to activate the immune system properly for protection can be impaired by either disease or therapies, resulting in less than adequate protection. Anyone considering the additional dose under this classification should consult with their provider to ensure that the appropriate individual assessment of risk/benefit is considered.

Which brings me to boosters in general. Recently, through a series of revisions, the CDC recommended booster shots of all three COVID-19 vaccines for everyone ages 18 and older. The basis for this recommendation is the decrease of the immune response that is common to vaccines over time and concerns of new variants that may be more transmissible. For these vaccines specifically, the waning response usually occurs within six to eight months. Therefore, those who received the two-dose regimen for the m-RNA (Pfizer-BioNTech or Moderna) vaccines should get a booster six months later. For those who received the single-dose vaccine (Johnson & Johnson), booster shots are recommended two months later. This “reminder” allows our bodies to continue recognizing the foreign microorganism and what needs to be done to eliminate it.

Vaccines are safe and effective, but like all medications, consultation with your provider is important as you consider additional doses or a booster. As holiday gatherings and events increase, as winter weather ushers us inside more, and as new variants loom, it’s also important to get your questions answered sooner rather than later. Combined with mask-wearing, covering your coughs and sneezes, and washing your hands often, the COVID-19 vaccines are critical to ending the pandemic.

Francisco R. Velázquez, M.D., S.M., is the Spokane Regional Health District health officer.