The Importance of COVID-19 Booster Dosing for the Immunocompromised

In late September, the Food and Drug Administration (FDA) stated it would grant an Emergency Use Authorization (EUA) for a booster dose of the Pfizer-BioNTech COVID-19 vaccine, BNT162b2 (Comirnaty), for three population groups including: people 65 years and older; people 18 through 64 years who are deemed high risk of severe infection including people who are immunocompromised; and those people 18 through 64 years with jobs that put them at high risk, such as health care workers.

That same week, the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP) met and decided to recommend the Pfizer-BioNTech COVID-19 vaccine booster dose for immunocompromised populations including:

• persons 50-64 years with underlying medical conditions at least 6 months after the primary series under the FDA’s EUA.
• And in persons based on individual benefit and risk who are 18-49 years with underlying medical conditions at least 6 months after the primary series under the FDA’s EUA.

And while the agencies made it clear that people ages 18-64 years old with underlying medical conditions would be eligible for the booster doses, it remains unclear who within this diverse patient population are really in need.

In thinking about these populations who may need a booster dose, it is really about who is at a greater risk of contracting COVID-19 as well as gauging the population’s response to their initial vaccine. The immunocompromised population incorporates a large, diverse group that have varying health issues. For some who are organ-donation recipients or have uncontrolled diseases or conditions, they may be at a higher risk for COVID-19, according to Daniel Streetman, PharmD, MS, manager of referential content in the Metabolism, Interactions, & Genomics group for Clinical Effectiveness at Wolters Kluwer, Health. “The actual magnitude of the risk depends on how significantly someone’s immune system is suppressed. There are people on really high doses of immune suppressing drugs or people with autoimmune diseases that are extremely active and not very well-controlled to be at a greater risk.”

In addition, Streetman points out it also has to do with the effectiveness of the vaccine for these groups during their first rounds of vaccination. “There are studies where if you look at antibody response of the vaccine in some solid organ transplant recipients, the antibody response is really low—20 to 30%. Yet, you have other immunocompromised individuals that have autoimmune diseases that are pretty-well controlled or patients with HIV whose disease is very well-controlled and antibody response is greater than 80%,” Streetman said.

Contagion spoke to Streetman about the impact of the Delta variant on the immunocompromised, their incidence rates of breakthrough infections, and further insights on vaccine effectiveness in these groups.