FDA amended the mRNA vaccine EUAs to allow for third doses for immunocompromised people as expected. ACIP meets today to discuss guidance for this change. Should clear the way for physicians to start giving third doses to patients by the end of today.
This change applies to solid organ transplant recipients or people with equivalent level of immunocompromise. This is the group that consistently is the highest non-responder to the standard vaccine series. Fortunately studies indicate the third dose for the non-responders allows 33-50% to respond. A concern was that the third dose would cause rejection in organ transplant recipients, but studies indicate the third dose was safe.
This group is especially prone to breakthrough infections. A significant number of breakthrough hospitalizations have been immunocompromised individuals. And they represent a high risk of creating variants when infected as they can have prolonged infections.
As for everyone else, the FDA and CDC are monitoring different vaccinated cohorts with frequent weekly testing. If they see immunity waning and more breakthrough disease in these cohorts there will be a move to push boosters for other groups. At the moment there is no indication that boosters are needed for the general population. Fauci expects we will all eventually need boosters, but not at this time.