RECEIVED A HALF DOSE FOR THEIR BOOSTER DOSE; OFF LABEL USE; This spontaneous report received from a health care professional concerned a 26 year old male of unspecified race and ethnicity. The patient's height, and weight were not reported. No past medical history or concurrent conditions were reported. The patient previously received covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin not reported, batch number: unknown expiry: unknown) dose was not reported, 1 total, administered on unspecified dated for prophylactic vaccination (manufacturer not otherwise specified, dose number in series 1). The patient received covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin not reported, batch number was either or 211A21A (batch/lot number also reported by HCP as: 1822809) expiry: UNKNOWN) 0.25 ml (milliliter), frequency one total, administered on 28-NOV-2021 for prophylactic vaccination (dose number in series 2). No concomitant medications were reported.  On 28-NOV-2021, the patient received a half dose for their booster dose (captured as: Vaccine under dose) and off label use (dose number in series 2). The reporter stated that something was printed and was disseminated which said to administer 0.25ml. As reported in source document, HCP (health care provider) was transferred to MICC (unknown acronym definition) for further assistance. HCP (from public health dept) stated that there were 33 patients who received half doses (0.25ml) for their booster or 3rd dose a few days ago. Most of them were patients from Texas. HCP stated that something was printed and disseminated that said to administered .25ml. HCP is not sure where that information came from. Stated it was over the holidays so people could have thought that info changed and staff was just not made aware. HCP did not think it has been reported yet through VAERS. HCP stated at the time of report that the vendor will file the report with VAERS, the the public health department. HCP stated that they figure it out after the event because they could not figure out how so many doses were given. They were looking for a discrepancy in the number of vials perhaps, but then realized that half doses were given. HCP consented to being contacted, but that she may not be the best person to contact. If she had an alternate contact she will provide it to whomever reaches out to her. HCP stated that Spartan is the vendor. They teamed up together to gather information and they may have called to report these events as well, so be mindful of possible duplicate reports.  The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The outcome of the received a half dose for their booster dose and off label use was not reported. This report was non-serious. This case, from the same reporter is linked to 20211202469, 20211202515, 20211200675, 20211201168, 20211201179, 20211201228, 20211201228, 20211201304, 20211201351, 20211201362, 20211201392, 20211201443, 20211201450, 20211201963, 20211202161, 20211202199, 20211200717, 20211200723, 20211200769, 20211200994, 20211201286, 20211202207, 20211202246, 20211202250, 20211202371, 20211202379, 20211201046, 20211204104, 20211220152, 20211220146, 20211220262, 20211220250, 20211220145, 20211220619 and 20211220155.