Influenza‐associated mortality in Thailand, 2006–2011

Abstract

BackgroundInfluenza-associated mortality in subtropical or tropical regions, particularly in developing countries, remains poorly quantified and often underestimated. We analyzed data in Thailand, a middle-income tropical country with good vital statistics and influenza surveillance data.MethodsWe obtained weekly mortality data for all-cause and three underlying causes of death (circulatory and respiratory diseases, and pneumonia and influenza), and weekly influenza virus data, from 2006 to 2011. A negative binomial regression model was used to estimate deaths attributable to influenza in two age groups (<65 and ≥65 years) by incorporating influenza viral data as covariates in the model.ResultsFrom 2006 to 2011, the average annual influenza-associated mortality per 100 000 persons was 4·0 (95% CI: −18 to 26). Eighty-three percent of influenza-associated deaths occurred among persons aged > 65 years. The average annual rate of influenza-associated deaths was 0·7 (95% CI: −8·2 to 10) per 100 000 population for person aged <65 years and 42 (95% CI: −137 to 216) for person aged ≥ 65 years.DiscussionIn Thailand, estimated excess mortality associated with influenza was considerable even during non-pandemic years. These data provide support for Thailand's seasonal influenza vaccination campaign. Continued monitoring of mortality data is important to assess impact.

Reply to Alonso et al. “Bangladesh and Rwanda: Cases of high burden of influenza in tropical countries?”

“…Estimates from Kenya,5 South Africa,6 and Thailand7 are comparable to our estimates, and in some instances, higher than estimates for Bangladesh. As such, we do not consider the mortality estimates (6‐11 per 100 000 population) in Bangladesh to be high when compared to other countries; however, we do consider 6‐11 deaths per 100 000 population to be a substantial burden for the country of Bangladesh.…”

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“…During the 6-year study period, a total of 60 795 specimens were 14 Singapore, 16 Thailand, 17 United…”

Assessment of potential public health impact of a quadrivalent inactivated influenza vaccine inThailand

“…32 Further, we believe that a mortality rate based on hospital-based surveillance is likely to underestimate mortality because it will not include out-of-hospital mortality and mortality that might occur from influenza-associated complications after virus is no longer detectable. The mortality rates derived from the surveillance were indeed lower than recent reports from Thailand by Cooper et al 33 and Aungkulanon et al 34 Reviewing the published literature to gather input parameters for the model highlighted important gaps in influenza knowledge in Thailand. In particular, we found few estimates of vaccine effectiveness for countries in the Southern Hemisphere in general, and Thailand in particular.…”

“…The mortality rates derived from the surveillance were indeed lower than recent reports from Thailand by Cooper et al . and Aungkulanon et al . (6·1 annual deaths per 100 000 population for 2005–2009 and 4·9 deaths per 100 000 population for 2006–2011).…”