It would take several months to develop and distribute a vaccine capable of combating a winter flu pandemic, Birmingham City Council has admitted.
The first wave of a previously unidentified virus would have "come and gone", potentially with devastating effect, before an antidote could be produced.
The council, responding to a Freedom of Information Act request by The Birmingham Post, said it was talking to official bodies
about drawing up priority groups to receive the vaccine first in the event of a pandemic or outbreak of avian bird flu.
Sonya Cerutti, the council's information governance manager, said: "A flu pandemic would be different from the usual seasonal occurrence in a number of ways.
"It results when a new influenza virus emerges which is very different from recently circulating strains and is capable of spreading rapidly from person to person and causes illness in a high proportion of those infected.
"To develop a new vaccine will take several months and it is therefore likely that the first wave of the pandemic may well have come and gone before the vaccine has been produced.
"Working with the World Health Organisation, preparatory work is already being undertaken so that the lead in time is as short as possible.
"Once the vaccine has been developed it is our understanding that it is the intention of the Department of Health to secure enough supplies to vaccinate the entire population.
"Nevertheless, vaccine will have to be distributed equitably, and national recommendations are for a tiered approach as vaccine supplies come on stream, administered first to pre-determined priority groups."
As a fall-back position, the Department for Health was building up stockpiles of antivirals but it was not known how effective against a new strain of flu they would be or how long it would take to produce sufficient supplies.
Ms Cerutti added: "Since pandemic influenza will represent a major challenge, the council is collaborating closely with the health service and other agencies."
She said final decisions about who should qualify for the vaccine first would be made by the UK National Influenza Pandemic Committee, which would take advice from the Joint Committee on Vaccination and Immunisation.
The UKNIPC would base its decisions on principles outlined in the Department of Health Contingency Plan, which lists priorities as protecting healthcare workers occupationally most at risk, preventing sickness absence among workers in essential services and preventing illness in vulnerable groups.
Ms Cerutti added: "In the absence of vaccines in the first wave, the Department of Health has recommended use of 'antivirals' to reduce the health impact associated with infection.
"Their effectiveness in this regard is uncertain and will need to be reviewed when used. Nevertheless, the Department of Health is building up stockpiles of these antivirals and our understanding is that enough antivirals will be available to treat all anticipated cases.
"However, there will be a delay before manufacturers can make sufficient stocks for the UK to build up a stockpile."