The World Health Organisation said the swine flu pandemic virus would spread again next winter in the northern hemisphere and recommended its inclusion in the regular influenza vaccine.
Protection against two other seasonal strains should be incorporated along with the A(H1N1) pandemic strain that swept across the world last year, the UN health agency said after a biannual meeting of flu vaccine experts.
The recommendation came as the WHO estimated that some 200 million people worldwide had received a dedicated anti-pandemic jab since it was offered late last year.
"The recommendation is a separate issue from whether the pandemic is over. No it is not over," said Keiji Fukuda, special adviser to the WHO Director-General on pandemic influenza.
"We hope that the worst is over and overall trend is going down," he told journalists.
Viruses included in the annual seasonal vaccines - in minute doses to trigger the immune system - are regarded as a likely "significant threat," especially for young children, the infirm and the elderly.
The UN health agency had already made a similar recommendation last September for the southern hemisphere seasonal flu vaccine for this year.
Experts adjust the seasonal vaccine cocktail twice a year for the northern and southern hemispheres, about eight months ahead of the onset of their cold seasons.
Pharmaceutical companies rushed through a separate vaccine for A(H1N1) last year after the new swine flu strain was uncovered in Mexico and the United States last April, prompting the WHO to declare a pandemic as the virus spread swiftly into more than 200 countries.
Several countries have since been seeking to offload costly and unused emergency stocks or orders of dozens of millions of doses of dedicated swine flu vaccine.
As the A(H1N1) virus spread in Senegal and Mauritania, but largely waned elsewhere, Mr Fukuda said some countries might need still a dedicated pandemic vaccine.
The African case "is a very good reminder that what we see in some parts of the world such as Europe and North America is not necessarily what we will be seeing in other parts of the world at the same time," he added. Otherwise, while it was "theoretically possible" for pharmaceutical firms to divert components of pandemic vaccine into the new seasonal jabs, vaccine in syringes and vials could not be recycled.
The WHO recommendations said: "It is expected that A(H1N1) pandemic 2009, A(H3N2) and B viruses will co-circulate in the northern hemisphere 2010-2011 with the likelihood that the pandemic A(H1N1) 2009 viruses will predominate."
Although more than 15,000 people have died worldwide in the pandemic, the new virus turned out to be less dangerous than at first thought.
The WHO's emergency panel of swine flu experts is to meet next Tuesday to formally determine whether the pandemic has passed its peak.