6 research outputs found
Revaccination strategies to maximize duration of herd immunity (DHI).
<p>(<b>A</b>) Recurring mass vaccination events (arrows) with 100% coverage of susceptible people every year (dashed line) or two years (dotted line) is shown to periodically achieve then lose herd immunity, designated by the horizontal line at <i>R</i><sub><i>e</i></sub> = 1. Faded horizontal bars show times with herd immunity under each strategy and the total DHI is annotated to the right of each. (<b>B</b>) Routine vaccination of 2.4% (green), 3.6% (teal), or 4.8% (purple) of the population per month achieve herd immunity for 0, 4.4, and 4.3 years, respectively. (<b>C</b>) A āMass and Maintainā strategy with one-time vaccination at 75% coverage followed by routine vaccination of 2.4% (green), 3.6% (teal), or 4.8% (purple) of the population per month can render herd immunity for 1.6, 5.2, and 4.3 years, respectively. The following are held constant for all simulations: population size = 10,000; maximum vaccine courses = 30,000; <i>R</i><sub>0</sub> = 1.5; migration rate = ; and birth and death rates = .</p
Vaccine targeting optimized in settings with intermediate rates of migration.
<p>Vaccine impact, as measured by the difference in the cumulative probability of an outbreak comparing a mass kOCV campaign (coverage 100%) versus no vaccination, is shown to reach maxima (triangles) at intermediate levels of mobility (x axis). The time since vaccination (colored lines) modifies these maxima. Grey dashed lines denote the estimated migration rates for Calcutta, Bentiu PoC Camp, and Dhaka. In this example, <i>R</i><sub>0</sub> = 1.5 and the average probability that a migrant is infected is 1/<i>N</i>, where <i>N</i> is the population size.</p
Dynamics of population susceptibility and herd immunity.
<p>Dynamics following mass vaccination (100% coverage) with kOCV (left column) or a hypothetical vaccine with VE = 1 indefinitely (right column). (<b>A-B</b>) Population susceptibility increases over time in the presence of migration rates of (solid line), (dashed line), and zero (dotted). (<b>C-D</b>) The effective reproductive number changes over time with X(t) differently for settings with basic reproductive numbers of 2 (red), 1.5 (green), and 1 (blue). (<b>E-F</b>) The probability that a single case sparks an outbreak of more than 10 cases. Birth and death rates are set to zero in each simulation.</p
Relative contribution of four potential drivers of waning herd immunity in Bentiu PoC Camp.
<p>Relative contribution of four potential drivers of waning herd immunity in Bentiu PoC Camp.</p
Bentiu PoC Camp case study.
<p>(<b>A</b>) Reported population size of the Bentiu PoC Camp (blue line), approximate number of people vaccinated assuming two-dose coverage (green bars), and monthly case counts from October to January (inset grey bars). IOM began reporting entries and exits in December 2015, which are represented by the faint green and red ribbons around the blue line. (<b>B</b>) The proportion susceptible over time (green line) decreases due to mass vaccination events and increases over time since vaccination. (<b>C</b>) The probability that a single case sparks an outbreak of more than 10 cases increases with <i>X</i>(<i>t</i>) and R<sub>0</sub>, as represented by line color: R<sub>0</sub> = 1 (blue); 1.5 (green); 1.8 (black); and 2 (red). For reference, R<sub>e</sub> = 0 yields an outbreak probability of 0; R<sub>e</sub> = 1.01 yields a probability of 0.25; R<sub>e</sub> = 1.35 yields a probability of 0.50; R<sub>e</sub> = 1.84 yields a probability of 0.75; and R<sub>e</sub>>4.66 yields an outbreak probability over 99%.</p
Coffee Rings as Low-Resource Diagnostics: Detection of the Malaria Biomarker <i>Plasmodium falciparum</i> Histidine-Rich Protein-II Using a Surface-Coupled Ring of Ni(II)NTA Gold-Plated Polystyrene Particles
We report a novel, low-resource malaria
diagnostic platform inspired
by the coffee ring phenomenon, selective for <i>Plasmodium falciparum</i> histidine-rich protein-II (<i>Pf</i>HRP-II), a biomarker
indicative of the <i>P. falciparum</i> parasite strain.
In this diagnostic design, a recombinant HRP-II (rcHRP-II) biomarker
is sandwiched between 1 Ī¼m NiĀ(II)Ānitrilotriacetic acid (NTA)
gold-plated polystyrene microspheres (AuPS) and NiĀ(II)ĀNTA-functionalized
glass. After rcHRP-II malaria biomarkers had reacted with NiĀ(II)ĀNTA-functionalized
particles, a 1 Ī¼L volume of the particleāprotein conjugate
solution is deposited onto a functionalized glass slide. Drop evaporation
produces the radial flow characteristic of coffee ring formation,
and particleāprotein conjugates are transported toward the
drop edge, where, in the presence of rcHRP-II, particles bind to the
NiĀ(II)ĀNTA-functionalized glass surface. After evaporation, a wash
with deionized water removes nonspecifically bound materials while
maintaining the integrity of the surface-coupled ring produced by
the presence of the protein biomarker. The dynamic range of this design
was found to span 3 orders of magnitude, and rings are visible with
the naked eye at protein concentrations as low as 10 pM, 1 order of
magnitude below the 100 pM <i>Pf</i>HRP-II threshold recommended
by the World Health Organization. Key enabling features of this design
are the inert and robust gold nanoshell to reduce nonspecific interactions
on the particle surface, inclusion of a water wash step after drop
evaporation to reduce nonspecific binding to the glass, a large diameter
particle to project a large two-dimensional viewable area after ring
formation, and a low particle density to favor radial flow toward
the drop edge and reduce vertical settling to the glass surface in
the center of the drop. This robust, antibody-free assay offers a
simple user interface and clinically relevant limits of biomarker
detection, two critical features required for low-resource malaria
detection