"It's not too late to get vaccinated but it does take a couple of weeks to kick in, we have seen the rate of influenza go up a lot in the past week," Dr Peterson said.
"Interestingly enough, the elderly and chronically ill aren't any more likely to get the illness, but they are more likely to get the very bad consequences. But even fit young people can be hospitalised by the flu."
The vaccine is free for many people with chronic illnesses until the end of this month. Pregnant women are also funded for the injection, which has proven to be highly effective in preventing influenza and its complications in women and children for a short time after birth.
"This year we had an issue with the vaccine being slightly late because they reconstructed it to meet changes in the virus, it seems those changes that were made match the strains of influenza which are most prevalent at the moment."
Hawke's Bay Hospital had seen a boost in people suffering its effects, chief medical officer John Gommans said.
Shortness of breath and chest infections were lead causes of recent hospital presentations and admissions, mostly concerning elderly people.
Dr Gommans said prevention was key, advising anyone who felt sick to see their GP before the illness resulted in something more serious.
While the flu virus could not be cured with antibiotics, it was important to keep coughs and other respiratory niggles in check.
"We have seen a big increase in flu-like illness over the past couple of weeks particularly amongst the elderly, and getting to see a doctor early can make a big difference," he said.
Influenza was highly contagious and could be spread to others within a two metre radius - it can be caught even before symptoms have developed.
Once infected it was important to get bed rest and stay hydrated.
