Resume:
2つの方法を利用した風疹のワクチン接種の優先的接種のモデル化
Hiroshi NishiuraDepartment
ofHygiene
GraduateSchool of MedicmineHokkaido
University
Resumeof
forthcoming
articleAsan
original study
isexpected
tobeprinted
elsewhere,
herewithaResumeofthestudy
isprovided
forthisproceedings.
Background
Rubella isa
contagious
viraldisease,
causedby
rubella virus anddirectly
transmitted from humantohuman. The infection is often mild andsymptoms
lastonaveragefor 1 to3
days.
However,
ifpregnant
women areinfectedduring
theirearly
gestational
ageofpregnancy,
the infectioncould also influencefetus,
leading
toa cause ofcongenital
rubellasyndrome
(CRS).
OnceCRS occurs,itinducesserious incurable illness and about 20% of CRS is consideredtoresultinmiscarriage.
For thisreason, adolescent femalehasbeenatarget
ofroutine immunizationas soonasthe vaccinewasdeveloped.
Later,
industrialized nationshave aimedtoelevate herdimmunity
sothat theepidemic
itselfcanbecontrolled.Nevertheless,
anepidemic
ofrubellawas seenfrom2013‐15,
involving mostly
adults, especially
adult males.Itisatragedy
thatasmanyas 45 CRScaseshave been confirmed and notifiedtothegovemment.
Theepidemic
wasconsideredtohave been causedby
apolicy
failure ofprevious
vaccination program that has led thepresentday
30s‐50s malesusceptible
torubella.Nowaneffectivesupplementary
vaccination program hastobeconsidered,
and such program hastobesupported by objective
scientific evidenceasassistedby
mathematical models. Whenconsidering
thesupplementary
vaccination and revaccination amongsusceptible
pockets
inadults,
itis vitaltoidentify
themostcost‐effectivestrategy
ofvaccination. This isparticularly
the casewhenanepidemic
sporadically
occurs,because thecountry
wouldnothave sufficient stock of vaccinestobeput
intoplace.
The purposes of the
present
study
weretwo‐fold. Onewastoidentify
themost economical vaccinationstrategy,
anticipating
similar future rubellaepidemics.
The otherwastoestimate therequired
minimum vaccination dosestoensurethatthemajor
epidemic
wouldnothappen.
数理解析研究所講究録
Method
Modeling
strategyUsming
amathematicalmodel,
wereconstructthe transmissiondynamics
ofrubella in 2012‐13 anduseitforplanning
futurecontrol. Thereweretwotasks.Onewastocharacterize theageand
gender specific
transmissiondynamics.
Weemployed
theso‐ called multivariate renewal process,i.e.,
c_{aI} =s_{ai}(t)\displaystyle \sum_{j}2^{R_{abij}}\int_{0}^{t}c_{bj}(t-s)g(s)ds
todescribe the
temporal
evolution ofrubellaepidemic.
Theotherwasto
implement
multiple
scenariosvarying
targethost ofsupplementary
vaccination and revaccination. Modelparameterization
Thewayto
identify susceptible
individualsby
ageandgender
hasposed
aproblem
indefining
thebaseline,
becausesusceptibles
canbemanually
identified intwodifferent ways.Oneisto trustseroprevalence
data,
asindicating
the fractionprotected.
Theother istoexplicitly quantify
thenextgeneration
matrix usin\mathrm{g}theage andgender
stratified data.Forbothmethods,
wehave used the age‐ andgender‐specific
contactrates. Results/DiscussionAnalyzing
bothcases,weshowed thatvaccinating
30\mathrm{s}male isoptimal.
Toachieveoptimal
vaccination,
thesupplementary
vaccination and revaccination shouldnot involve female and shouldnotinvolve40\mathrm{s}male. Itwasalso shown thatsecuring
7.4 million vaccines wouldhelp
reduce thereproduction
numbertobe below1.0. Address forcorrespondence:
Department
ofHygiene
Graduate School of Medicin\mathrm{e} HokkaidoUniversity
Sapporo
060‐8638 JAPAN\mathrm{E}‐mail address: