Seasonal vaccine 'protects' against swine flu

The seasonal flu vaccine provides some protection against swine flu, particularly the most severe forms, doctors have said.

However, the authors of the study published in the British Medical Journal (BMJ) today, have warned their results should be 'considered cautiously'.

Despite the positive results of their preliminary research, the authors of the study said the seasonal flu vaccine should in no way be a replacement for the vaccination against the swine flu pandemic.

The study has been led by Dr Jose Luis Valdespino from Mexico, who investigated the link between the 2008-9 seasonal flu vaccine with cases of influenza A/H1N1 during the epidemic in a speciality hospital in Mexico City.

The authors say the reason the seasonal vaccine offers some protection is because it boosts existing antibodies in individuals who have previously been exposed to a similar flu virus, either by infection or vaccination.

In June the World Health Organisation (WHO) raised the pandemic alert of the flu virus from phase three to phase six.

Dr Valdespino and his colleagues compared the health outcomes of 60 patients with swine flu and 180 control patients with other diseases. Both groups of patients informed the authors directly, by telephone or via a close relative whether they had received the 2008-9 seasonal flu vaccine.

The results showed that the uninfected participants were significantly more likely to have received the seasonal flu vaccine and suggest that it protected them against particularly severe forms of swine flu. However the authors say the results must be taken in context and argue that given the small sample size 'it will be key to conduct similar studies in other settings to confirm or refute our results'.

In an accompanying editorial, Dr Menno de Jong from the Academic Medical Centre of the University of Amsterdam added: 'To protect against seasonal and pandemic strains, vaccines and vaccine production need to improve.'