Completing a primary vaccine series means receiving:
A 2 – dose series of an mRNA COVID-19 vaccine (Pfizer-BioNTech and Moderna), OR
A single does of Janssen COIVD-19 vaccine
A booster dose is another dose of vaccine administered after receiving a primary vaccine series to enhance or restore protection which might have subsided over time
An additional dose is another dose of vaccine administered to people who were less likely to mount a protective immune response after initial vaccination. People who are moderately or severely immunocompromised should receive an additional dose.
Difference between Booster and Additional Dose
The dose counts as a booster: If no further details are provided, count these doses as boosters (rather than additional doses) for NHSN
The dose counts as an additional: only if there is specific documentation indicating additional doses were administered due to the individual having a moderately to severely immunocompromised condition.