Preliminary research published today on BMJ.com reports that the 2008-2009 seasonal flu vaccine (trivalent inactivated vaccine (TIV)) provides some protection against swine flu, particularly the most severe forms of the disease.
But the authors caution that the results should be considered carefully “and in no way indicate that seasonal vaccine should replace vaccination against pandemic influenza A/H1N1 2009.”
The World Health Organization raised the level of influenza pandemic alert from phase three to phase six in June 2009, when this new flu virus appeared. By July 2009, 122 countries reported almost 100,000 confirmed cases of swine flu.
Dr Jose Luis Valdespino from Mexico led this study to investigate the link between the 2008-2009 seasonal flu vaccine with cases of influenza A/H1N1 during the epidemic, in a hospital in Mexico City.
The researchers explain that the seasonal vaccine offers some protection because it boosts existing antibodies in individuals who have previously been exposed to a similar flu virus, either by infection or vaccination.
Valdespino and colleagues studied the health outcomes: hospitalization, mechanical ventilation and death. They compared 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 2008-2009 seasonal flu vaccine.
Findings indicated that the uninfected participants were significantly more likely to have received the seasonal flu vaccine. This suggests that it protected them against particularly severe forms of swine flu. However the authors say the results should be considered objectively. They 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 a supplementary editorial, Dr Menno de Jong from the Academic Medical Centre of the University of Amsterdam agrees with Dr Valdespino. He explains that the results do not imply that there is no need for a specific vaccine against swine flu.
In addition, Dr de Jong discusses the issue of vaccine production. He argues that vaccines may not be available in time, even in countries that have amounted sufficient quantities, so that “vaccinated people may be protected only after the peak of the pandemic has passed.” He comments that “to protect against seasonal and pandemic strains, vaccines and vaccine production need to improve.”
“Partial protection of seasonal trivalent inactivated vaccine against novel pandemic influenza A/H1N1 2009: case-control study in Mexico City”
Lourdes Garcia-Garcia, research professor,Jose Luis Valdespino-Gómez, epidemiologist, Eduardo Lazcano-Ponce, research professor, Aida Jimenez-Corona, research professor, Anjarath Higuera-Iglesias, epidemiologist, Pablo Cruz-Hervert, research professor, Bulmaro Cano-Arellano, engineer, Antonio Garcia-Anaya, engineer, Elizabeth Ferreira-Guerrero, epidemiologist, Renata Baez-Saldaña, research professor,Leticia Ferreyra-Reyes, research professor, Samuel Ponce-de-León-Rosales, infectious diseases specialist,Celia Alpuche-Aranda, infectious diseases specialist, Mario Henry Rodriguez-López, research professor,Rogelio Perez-Padilla, research professor, Mauricio Hernandez-Avila, epidemiologist
BMJ 2009; 339:b3928
doi:10.1136/bmj.b3928
“The future of influenza vaccines”
Menno D de Jong, professor of clinical virology, Rogier W Sanders,assistant professor of microbiology and immunology
BMJ 2009; 339:b4014
bmj.com
Written by Stephanie Brunner (B.A.)