Influenza remains on the increase in Toronto, with 428 confirmed cases of the flu in the third week of January.

So far this season, 1,035 people have been hospitalized with influenza or suspected influenza in Toronto and 56 people have died as of Jan. 24.

The numbers don’t include anyone who come down with flu and not been treated by a doctor.

School absenteeism also continues to rise as the total number of cases in Toronto has hit 3,072, above the previous 10-year average.

Those troubling numbers were reported by Toronto Public Health on Friday.

There were 427 cases of influenza A reported in the third week of January, and just one case of influenza B.

There was also a drop in institutional outbreaks, with eight reported cases, compared to 16 in the second week of January.

There have been a total of 155 institutional cases (hospitals, seniors homes, palliative care centres, for example) reported this season.

Worst hit in the third week of January were seniors over the age of 65, with 271 reported cases. There were 59 cases for the 45 to 64 age group and 54 for residents from 25 to 44 years of age. There were three cases for infants and 18 cases for toddlers between one and four.

No new strains of influenza were reported in Toronto for the third week of January.

Meanwhile, a new study suggests this year’s flu vaccine has offered little or no protection in Canada against becoming sick enough to require medical care.

The newly released study on flu vaccine suggests it offers even less protection than was seen in an American study that was released earlier this month.

The U.S. study had suggested that the vaccine lowered a recipient’s risk of contracting the flu and getting sick enough to need medical care by 23 per cent.

That’s well below the 50 to 70 per cent effectiveness estimate that is often given for flu vaccine.

Lead author Dr. Danuta Skowronski says the problem this year is that nearly all flu infections so far in Canada have been caused by H3N2 flu viruses, and virtually all the viruses spotted in Canada are different from the one in the vaccine.

The Public Health Agency of Canada in December reported that the H3N2 influenza virus had mutated since this season’s flu vaccine was developed, leading to a larger than usual number of illnesses.

In the United States, H3N2 is also the main strain causing illness, but about one-third of the viruses there were a match for the H3N2 component of the vaccine.

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The Canadian study suggests that people who didn’t get a flu shot last year got more protection from this year’s vaccine than those who were vaccinated both years running.

The study is in Eurosurveillance, an online journal published by the European Centre for Disease Control.

With files from Helen Branswell, The Canadian Press