Just 66 per cent of eligible people in Canterbury have had a booster shot as visitors to Christchurch Hospital are being permitted under compassionate grounds only.
Data from Canterbury District Health Board shows the booster rate in the region is lagging behind the 100 per cent rate for the first dose of the vaccine.
"With Omicron the booster dose makes such a huge difference to the protection from Omicron and it's vital that anyone aged over 18 who had their second dose three or more months ago gets their booster dose as soon as possible.
"With a booster dose on board, most people are 95 per cent protected against serious illness or hospitalisation," a spokesperson said.