NHS England data shows 97% of the 5,948 health care workers at North Tees and Hartlepool NHS Foundation Trust had received at least one vaccination by the end of December – meaning 183 were unvaccinated at that point.
The figures also show 5,627 workers (95%) had received two jabs and 4,640 had received a booster dose (78%).
The Government's mandatory vaccination rules mean that NHS staff must have received a first jab by February 3 and be fully vaccinated by April 1 to continue in frontline roles.
Despite calls to delay the policy, the Department for Health and Social Care (DHSC) says there are no plans to extend the deadline and that ensuring staff are vaccinated is the "right thing to do".
In England, 94% of healthcare workers had received at least one vaccination by December 31 but over 85,000 were still unvaccinated.
The NHS Confederation, which represents the whole healthcare system, said there were risks as well as benefits to a mandatory approach.
Chief executive Danny Mortimer said: "Most health leaders support the introduction of a mandate but would have preferred longer to implement the policy.
“While the majority of health and care workers have been vaccinated, even small reductions in staffing numbers can cause disruption.”
A DHSC spokesperson said: “Health and social care workers look after the most vulnerable people in society, who could face serious consequences if exposed to the virus.
"Ensuring staff are vaccinated is the right thing to do to protect patients.”