Plasma halves swine flu death rate, study finds
Treatment using antibodies from the blood plasma of recovered swine flu patients can more than halve the mortality rate for those who suffer severe complications from the deadly disease, Hong Kong researchers have found.
The death rate among patients given the plasma treatment during a research project that began in August last year was 20 per cent - against almost 55 per cent for those not given it.
Results of the University of Hong Kong microbiology research team's project appear in the journal Clinical Infectious Diseases today.
In the HK$3 million project, the university's microbiology department and the Red Cross Blood Transfusion Service collected plasma from recovered swine flu patients in the city. The team then conducted research on 93 adult patients with severe swine flu infections admitted to intensive care units at public hospitals from September 2009 to June last year. Most of these patients were admitted to the units three days after developing flu symptoms.
Of them, 20 were given the plasma collected from recovered patients, known as 'convalescent plasma', while the rest did not receive any.
Both groups had taken the anti-viral medicine Tamiflu but did not respond well to the medicine.
The university's head of microbiology, Professor Yuen Kwok-yung, a member of the research team, said the mortality rate was 20 per cent for the 20 patients who received the plasma. This compares to the much higher 54.8 per cent for the 73 patients in the non-treatment group.
The treatment and control groups were matched by age, sex and severity of their conditions. None of the patients developed adverse effects from the plasma treatment.
'It is encouraging that our study has proven the effectiveness of the convalescent plasma treatment. Tamiflu is useful if it is taken early enough. The plasma can reduce the virus load significantly and also the inflammatory response of the patients,' Yuen said.
Yuen said controlling inflammatory responses was a key to swine flu treatment. Many patients died of multi-organ failure caused by deadly responses such as pneumonia, liver or kidney failure.
The worldwide pandemic and seasonal flu activity have abated since last year's peak but scientists are still racing to find new weapons against the virus.
Antivirals such as Tamiflu are effective only if they are given early enough - preferably within 48 hours of the onset of illness - and rising drug resistance also means an alternative treatment is needed. Antibody treatment does not have the problem of drug resistance that antivirals have, the research team says.
Hong Kong's current stock of convalescent plasma, which will expire in about a year, is enough to treat 50 severerly ill patients. Yuen said swine flu had died down in Hong Kong recently but might return - in which case more of the plasma would be needed.
The H1N1 swine flu virus surfaced in Mexico in March 2009. The World Health Organisation declared a pandemic in June after 74 countries and territories reported cases. It broke out in more than 200 countries and killed at least 18,209 people. In Hong Kong, more than 280 patients had severe complications and at least 80 died.
In 2003, the university developed a similar antibody therapy for Sars patients but there was insufficient data to show its effectiveness.