Authors' reply

doi:10.1136/bmj.b4978

Published 24 November 2009, doi:10.1136/bmj.b4978
Cite this as: BMJ 2009;339:b4978

Letters

Seasonal vaccine and H1N1

Authors’ reply

The first 150 words of the full text of this article appear below.

Skowronski and colleagues question the effectiveness of seasonalvaccine against pandemic A/H1N1 flu observed in our study.¹The confidence intervals are wide and similar to those describedwhen seasonal flu vaccine strains are not antigenically wellmatched to circulating endemic strains (27% to 65%).² Evidenceon the effectiveness of seasonal vaccines against pandemic strainsindicates some degree of protection against antigenically differingflu strains.³ ⁴ ⁵ Therefore the effectiveness we observed inour study is likely to be real.

We do not agree that cases and controls emerged from differentsource populations. Both cases and controls came from the populationthat is served by the study hospital and resides in the geographicalarea that had most of the flu cases during the study. Althoughthe hospital is a specialist hospital, a considerable proportionof its patient population (both cases and controls) is not referredas the referral system is poor. Differences between . . . [Full text of this article]

Lourdes Garcia-Garcia, research professor¹, Jose Luis Valdespino-Gómez, epidemiologist²

¹ Instituto Nacional de Salud Pública, Cuernavaca, Mor, Mexico, ² Laboratorios de Biológicos y Reactivos de México (BIRMEX), Distrito Federal, Mexico

jvaldespinog@birmex.gob.mx

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