LIVERPOOL, UK - 13 July 2010: Over half of UK swine flu hospital admissions and inpatient deaths occurred in people with no underlying health problems or obvious risk factors, research at the University of Liverpool has found.
The data back up the Government's policy of prioritising pregnant women, the under-fives, and those with long-term respiratory problems for vaccination against swine flu. But they also suggest that everyone with asthma might benefit from vaccination, not just those with severe disease, and they question whether a high fever helps to decide who has swine flu infection.
Dr Calum Semple, Senior Lecturer in Child Health at the University of Liverpool and Consultant Respiratory Paediatrician at Alder Hey Children's Hospital, said: "At the start of the 2009 Swine Flu pandemic we were able to establish rapid access to children's and adults' clinical data in the North of England and Wales by making use of the existing Comprehensive Local Research Network and Medicines for Children Research Network.
"The study found that well over half of hospital admissions and deaths occurred in previously healthy people. Hospital admissions were highest in children under the age of five years and pregnant women.
The findings support the vaccination of pregnant women - which may also protect their soon-to-be-born children - and all children under five years of age."
The research, carried out by the Universities of Liverpool and Nottingham, was based on an analysis of clinical data from 55 hospitals in 20 urban areas during the first wave of the swine flu pandemic during May to September 2009. The data were collected as part of the Government's Influenza Clinical Information Network (FLU CIN) surveillance programme.
Between April 27 and September 30 2009, data were collected on 631 people with swine flu - 405 of them adults - admitted to the 55 hospitals. Their ages ranged from three months to 90 years. One in three (36%) were under 16 and one in 20 (5%) were aged 65 and older. Those from black and minority ethnic backgrounds made up over 60% of admissions.
Twenty seven patients were pregnant, representing 4% of admissions and 18% of women aged between 16 and 44. This indicates that pregnant women are around three times as likely to require hospital admission - once infected with swine flu - as women who are not pregnant.
On average, two days elapsed between the start of symptoms and hospital admission. The most common presenting symptoms were fever and cough in both adults and children. But around one in four adults and children did not have a fever on admission, and more than half did not have a high fever, prompting researchers to question the wisdom of using a high fever as a key symptom of swine flu infection.
Around one in eight (13%) were admitted to intensive care or a high dependency unit. One in 20 (5%) died. Risk factors for death included an abnormal chest x ray or raised levels of a protein indicative of inflammation (CRP), especially in those who were obese or with any underlying serious respiratory condition.
Just under half of the patients had underlying conditions - mostly asthma. But almost half of them were not routinely using inhalers or taking oral steroids, which suggests they had mild, rather than severe, disease. Over half of all admissions (55%) and inpatient deaths (59%) occurred in people with no previous health problems.
The research is published in Thorax.