@article{PAR00010523,
  title = {2009 {A}({H}1{N}1) seroconversion rates and risk factors among the general population in {V}ientiane capital, {L}aos},
  author = {{K}ieffer, {A}. and {P}aboriboune, {P}. and {C}repey, {P}. and {F}laissier, {B}. and {S}ouvong, {V}. and {S}teenkeste, {N}. and {S}alez, {N}. and {B}abin, {F}. {X}. and {L}onguet, {C}. and {C}arrat, {F}. and {F}lahault, {A}. and de {L}amballerie, {X}avier},
  editor = {},
  language = {{ENG}},
  abstract = {{O}bjective: {T}o assess 2009 {A}({H}1{N}1) seroconversion rates and their determinants within an unvaccinated population in {V}ientiane {C}apital, {L}aos. {M}ethods: {C}o{P}an{F}lu {L}aos, a general population cohort of 807 households and 4,072 participants was established in {M}arch 2010. {S}ociodemographic data, epidemiological data, and capillary blood samples were collected from all the household members in {M}arch, and again in {O}ctober 2010, in order to assess the level of antibodies to 2009 {A}({H}1{N}1) with the haemagglutination inhibition assay. 2009 {A}({H}1{N}1) seroconversion was defined as a fourfold or greater increase in titre between inclusion and follow-up. {D}eterminants for pandemic influenza infection were studied using the generalized estimating equations model, taking household clustering into account. {R}esults: {B}etween {M}arch and {N}ovember 2010, 3,524 paired sera were tested. {P}rior to the pandemic, our cohort was almost completely vaccine-naive for seasonal influenza. {T}he 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]). {P}articipants with lower baseline titres had significantly higher infection rates, with a dose-effect relationship. {O}dds ratios ({OR}s) 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. {H}aving 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]). {C}onclusion: {T}he determinants and age distribution for seroconversion within a vaccine-naive population were similar to those found in developed countries. {T}his pandemic was characterized by strong epidemiological determinants, regardless of geographical zone and level of development. {M}oreover, 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.},
  keywords = {{LAOS}},
  booktitle = {},
  journal = {{P}los {O}ne},
  volume = {8},
  numero = {4},
  pages = {e61909},
  ISSN = {1932-6203},
  year = {2013},
  DOI = {10.1371/journal.pone.0061909},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00010523},
}