ArticlePloS one2013
2009 A(H1N1) seroconversion rates and risk factors among the general population in Vientiane Capital, Laos.
Article in PloS one, 2013. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 11 papers.
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Who cites it
11 citing papers in PubMed, 12 citations in OpenAlex.
- Maternal Influenza Vaccination and the Risk of Laboratory-Confirmed Influenza Among Household Contacts Under the Age of Five in Mali.The American journal of tropical medicine and hygiene · 2019Trial
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- Article
- Influenza Transmission Dynamics in Urban Households, Managua, Nicaragua, 2012-2014.Emerging infectious diseases · 2018Article
- Relative incidence and individual-level severity of seasonal influenza A H3N2 compared with 2009 pandemic H1N1.BMC infectious diseases · 2017Article
- Household Transmission of Influenza Virus.Trends in microbiology · 2016Review
- Causal analysis of H1N1pdm09 influenza infection risk in a household cohort.Journal of epidemiology and community health · 2015Article
- A sero-epidemiological study of arboviral fevers in Djibouti, Horn of Africa.PLoS neglected tropical diseases · 2014Article
- Determinants of influenza transmission in South East Asia: insights from a household cohort study in Vietnam.PLoS pathogens · 2014Article
- Comparative community burden and severity of seasonal and pandemic influenza: results of the Flu Watch cohort study.The Lancet. Respiratory medicine · 2014Article
- Determinants of individuals' risks to 2009 pandemic influenza virus infection at household level amongst Djibouti city residents--a CoPanFlu cross-sectional study.Virology journal · 2014Article
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Authors and funding
12 authors at 7 institutions in 2 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
objectiveTo assess 2009 A(H1N1) seroconversion rates and their determinants within an unvaccinated population in Vientiane Capital, Laos.
methodsCoPanFlu Laos, a general population cohort of 807 households and 4,072 participants was established in March 2010. Sociodemographic data, epidemiological data, and capillary blood samples were collected from all the household members in March, and again in October 2010, in order to assess the level of antibodies to 2009 A(H1N1) with the haemagglutination inhibition assay. 2009 A(H1N1) seroconversion was defined as a fourfold or greater increase in titre between inclusion and follow-up. Determinants for pandemic influenza infection were studied using the generalized estimating equations model, taking household clustering into account.
resultsBetween March and November 2010, 3,524 paired sera were tested. Prior to the pandemic, our cohort was almost completely vaccine-naive for seasonal influenza. The overall seroconversion rate among nonvaccinated individuals (n = 2,810) was 14.3% (95%CI [13.0, 15.6]), with the highest rate for participants under 20 yo (19.8%, 95%CI [17.4, 22.4]) and the lowest rate for participants over 60 yo (6.5%, 95%CI [3.7, 10.4]). Participants with lower baseline titres had significantly higher infection rates, with a dose-effect relationship. Odds ratios (ORs) ranged from 76.5 (95%CI [27.1, 215.8]), for those with a titre at inclusion of 1∶10, to 8.1 (95%CI [3.3, 20.4]), for those with a titre of 1∶40. Having another household member with a titre ≥1∶80 was associated with a higher likelihood of immunity (OR = 3.3, 95%CI [2.8, 3.9]).
conclusionThe determinants and age distribution for seroconversion within a vaccine-naive population were similar to those found in developed countries. This pandemic was characterized by strong epidemiological determinants, regardless of geographical zone and level of development. Moreover, we detected pre-existing cross-reacting antibodies in participants over 60 yo, which could not have originated from former multiple vaccination as has been suggested elsewhere.
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