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conferenceseries
.com
Volume 5, Issue 6(Suppl)
J Infect Dis Ther, an open access journal
ISSN: 2332-0877
Euro Infectious Diseases 2017
September 07-09, 2017
September 07-09, 2017 | Paris, France
Infectious Diseases
6
th
Euro-Global Conference on
Comparison of screening method and cohort design to estimate pertussis vaccine effectiveness in Denmark,
2000-2014
Lara Ricotta
1,2,
J Nielsen
1
, P Valentiner-Branth
1
and
K Mølbak
1
1
epartment of Infectious diseases Epidemiology, Statens Serum Institut, Copenhagen, Denmark
2
European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control, (ECDC), Stockholm, Sweden
Background:
In Denmark, laboratory-confirmed pertussis is notifiable, and national laboratory, vaccination and population registries
permit individual data linkage for analysis. Since 1997, acellular pertussis vaccine has been delivered as a primary series (PS) of three
doses at 3, 5 and 12 months, with a pre-school booster at age 5. We estimated VE for children receiving PS versus unvaccinated
children, and for those receiving booster dose versus not having received the booster, comparing estimates from a screening method
and a cohort design (CD).
Methods:
The Danish civil registration number was used to link individual case laboratory data to vaccination and population
registries. We estimated PS VE by birth cohort from 2000 to 2014, and for the booster from 2000 to 2010, using both methods. For the
SM, VE was calculated for PS using the proportion of PS-vaccinated versus totally unvaccinated among cases, and in the population
to January 2015. For the CD, linked data was used to estimate time at risk among individuals in each birth cohort from birth or arrival
in Denmark, until tested positive for pertussis, moved out of country, death or end of study period. VE was estimated as 1 minus the
incidence rate ratio (IRR) between incidence rate (IR = cases/time at risk) among PS-vaccinated and IR for totally unvaccinated using
Poisson regression. For the booster, VE was estimated for the booster-vaccinated versus no-booster, independent of other vaccines
received.
Results:
From 2000 to 2015, 3621 confirmed cases were reported among 1,024,906 children in all birth cohorts. Using SM, the
median VE for PS was 89.1% (range 63.9% to 99.7%). For the CD, median VE was, 77.2% (range 38.2% to 96.2%). For the booster, SM
produced a VE median estimate of 94.0% (range 88.7% to 98.2%), compared to 57.2% (range 50.2% to 69.7%) using CD.
Conclusions:
This study shows that acellular pertussis vaccine is highly effective. However, VE estimates for children who received
PS, and for those who received booster, are substantially higher using SM than CD. CD incorporates the dynamics of time-at-risk
and produces a more robust VE estimates. Therefore, SM is likely to overestimate VE, and countries using this approach need to be
aware of this limitation. When individual data can be collected or linked, we recommend using the cohort design to obtain a more
valid VE estimate.
Biography
Lara Ricotta, she had completed her medicine in preventive medicine, Epidemiology, Public Health and Neurology from 2000-2008 and Preventive Medicine
Residency Program (PMRP) from 2010-2015 University of Bologna. She had worked with Istituto Superiore di Sanità, Rome, Italy from 2012 to 2014. And from
2015 to present she is working European Centre for Disease Prevention and Control (ECDC) Università di Bologna
lara.ricotta@gmail.comLara Ricotta et al., J Infect Dis Ther 2017, 5:6(Suppl)
DOI: 10.4172/2332-0877-C1-032