Neither is it clear whether any of the affected residents had received their second dose of the vaccine.
The outbreak occurred in the HSE-run St Joseph's Community Nursing Home Unit in Trim on January 20, where 25 residents tested positive.
A statement from the HSE said: " The first Covid-19 vaccine clinic was held in St Joseph’s Community Nursing Home Unit Trim, on January 12 and 13 last.
"All eligible residents and staff received the first dose.
"The second dose of the Covid-19 vaccine was delivered on February 2 to the staff and residents who were eligible to receive it.
"An Outbreak of Covid-19 was declared at the Community Nursing Unit on January 20.