Recent studies have shown that more than half of those who died from swine flu or were admitted to hospital during the first wave of the pandemic were healthy people with no obvious underlying risks.

Researchers at the University of Nottingham, who conducted a survey of swine flu patients across the United Kingdom, said everyone with asthma should be vaccinated for the flu and not just those with its severe manifestation.

"Our findings support the use of H1N1 pandemic vaccine in pregnant women, children aged less than five years and those with chronic lung disease as a priority, including patients with asthma, regardless of severity," the researchers said in their paper.

The paper, published in the British Medical Journal Thorax, reported that the findings were based on analysis of clinical data from 55 hospitals spread across 20 towns and cities in the first wave of the disease between May and September last year.

The sample size comprised patients in the age group of 3 to 90 years, of which about 35% were below 16 years of age and about five percent were aged 65 or order. Four percent of the sample size was pregnant when they contacted the disease.

The report said that pregnant women were more than three times as likely to need in-patient treatment at hospitals once they were infected with the H1N1 virus. Last month, the World Health Organization had warned that the swine flu pandemic was not yet over. India alone has reported about 300 cases of the flu in the last one month.

Major pharmaceutical companies across the world have since developed vaccines and governments have ordered millions of doses for state-sponsored immunization campaigns to reduce the pace of the virus across the world.