The number of people with flu-like illnesses in critical care units across the West Midlands region has risen.
NHS West Midlands said there were 88 patients with flu or suspected flu in critical care in hospitals in the region.
This compared to 56 people being treated on 23 December.
Dr Rashmi Shukla, regional director of public health, urged people vulnerable to the virus, including pregnant women, to get vaccinated.
Dr Shukla said: "It's not too late for those most at risk of infection to protect themselves by having the vaccine.
"Today's figures show that flu can be a severe illness for those most at risk including pregnant women and children and adults with long term conditions".
The warning comes as figures show that 39 people in the UK have now died of flu-like illnesses this winter.
All but three of them were infected with the H1N1 swine flu virus, while the remainder had influenza B, the Health Protection Agency data shows.
The figures were published as the government announced it is to relaunch an advertising campaign to raise awareness of how to guard against flu.
Dr Shukla added that people with mild symptoms of flu-like illnesses should stay away from hospitals to avoid spreading the infection.