the four COVID-19 vaccines available for use in the U.S. follow various dosing schedules. All four vaccines have been demonstrated to be highly effective against severe outcomes related to COVID-19 in clinical trials and postauthorization observational studies. However, given concerns about waning immunity and the emergence of novel variants, there is interest in understanding the potential role of alternative dosing strategies for these vaccines to augment or prolong their protective effect, including (but not limited to) administration of additional doses of each vaccine, schedules containing different products (“mix and matchâ€) and modified dosing intervals.
