GPs around the country are to be given stocks of last year's leftover swine flu vaccine as the virus claimed its 13th victim since November in the North.
Medics fear the outbreak will worsen in the coming weeks.
About 5,400 people are being treated for flu-like illnesses, and experts think numbers could double over the coming week.
Nine of those who died while suffering from the swine flu virus in Northern Ireland had underlying health conditions, the North's Public Health Agency said. Those who died ranged from children to a 67-year-old.
The HSE confirmed yesterday it was to supplement supplies of this winter's seasonal flu vaccine with stocks of the swine flu jab bought last year.
It has also placed an order for another 100,000 doses of the current seasonal flu vaccine as a precaution to ensure any person who wants to be immunised can receive it.
The older jab, which can be used until later this year, only protects against swine flu, whereas this winter's version also covers other strains of flu.
There are still about 900,000 leftover doses of swine flu vaccine in storage worth about €2.5m.
However, most of it will end up unused and destroyed because it will be out of date by next winter.
It emerged in recent days that cases of swine flu doubled last week and 26 people, including two pregnant women, are ill in intensive care.
"The HSE has 30,000 seasonal flu vaccines in stock and has ordered a further 100,000," a spokesperson said.
"The HSE will also deliver supplies of Pandemrix, the vaccine used during last year's H1N1 (swine flu) pandemic vaccination campaign, to GPs.
"As almost 90pc of seasonal flu cases at present are swine flu, this will ensure continuity of supply of vaccines against swine flu if infection rates, as expected, continue to rise."