<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Toon Braeye</style></author><author><style face="normal" font="default" size="100%">Kristiaan Proesmans</style></author><author><style face="normal" font="default" size="100%">Dieter Van Cauteren</style></author><author><style face="normal" font="default" size="100%">Ruben Brondeel</style></author><author><style face="normal" font="default" size="100%">Hens, Niel</style></author><author><style face="normal" font="default" size="100%">Elias Vermeiren</style></author><author><style face="normal" font="default" size="100%">Hammami, Naïma</style></author><author><style face="normal" font="default" size="100%">Rosas, Angel</style></author><author><style face="normal" font="default" size="100%">Adrae Taame</style></author><author><style face="normal" font="default" size="100%">Emmanuel André</style></author><author><style face="normal" font="default" size="100%">Lize Cuypers</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Personal characteristics and transmission dynamics associated with SARS-CoV-2 semi-quantitative PCR test results: an observational study from Belgium, 2021-2022.</style></title><secondary-title><style face="normal" font="default" size="100%">Front Public Health</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">ADOLESCENT</style></keyword><keyword><style  face="normal" font="default" size="100%">Adult</style></keyword><keyword><style  face="normal" font="default" size="100%">Aged</style></keyword><keyword><style  face="normal" font="default" size="100%">Belgium</style></keyword><keyword><style  face="normal" font="default" size="100%">Contact Tracing</style></keyword><keyword><style  face="normal" font="default" size="100%">COVID-19</style></keyword><keyword><style  face="normal" font="default" size="100%">COVID-19 Nucleic Acid Testing</style></keyword><keyword><style  face="normal" font="default" size="100%">COVID-19 Vaccines</style></keyword><keyword><style  face="normal" font="default" size="100%">Female</style></keyword><keyword><style  face="normal" font="default" size="100%">Humans</style></keyword><keyword><style  face="normal" font="default" size="100%">Male</style></keyword><keyword><style  face="normal" font="default" size="100%">middle aged</style></keyword><keyword><style  face="normal" font="default" size="100%">SARS-CoV-2</style></keyword><keyword><style  face="normal" font="default" size="100%">Vaccine Efficacy</style></keyword><keyword><style  face="normal" font="default" size="100%">Viral Load</style></keyword><keyword><style  face="normal" font="default" size="100%">Young adult</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2024</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2024</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">12</style></volume><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;&lt;b&gt;INTRODUCTION: &lt;/b&gt;Following harmonization efforts by the Belgian National Reference Center for SARS-CoV-2, semi-quantitative PCR test (SQ-PCR) results, used as a proxy for viral load, were routinely collected after performing RT-qPCR tests.&lt;/p&gt;

&lt;p&gt;&lt;b&gt;METHODS: &lt;/b&gt;We investigated both the personal characteristics associated with SQ-PCR results and the transmission dynamics involving these results. We used person-level laboratory test data and contact tracing data collected in Belgium from March 2021 to February 2022. Personal characteristics (age, sex, vaccination, and laboratory-confirmed prior infection) and disease stage by date of symptom onset were analyzed in relation to SQ-PCR results using logistic regression. Vaccine effectiveness (VE) against a high viral load (≥10 copies/mL) was estimated from the adjusted probabilities. Contact tracing involves the mandatory testing of high-risk exposure contacts (HREC) after contact with an index case. Odds ratios for test positivity and high viral load in HREC were calculated based on the SQ-PCR result of the index case using logistic regression models adjusted for age, sex, immunity status (vaccination, laboratory-confirmed prior infection), variant (Alpha, Delta, Omicron), calendar time, and contact tracing covariates.&lt;/p&gt;

&lt;p&gt;&lt;b&gt;RESULTS: &lt;/b&gt;We included 909,157 SQ-PCR results of COVID-19 cases, 379,640 PCR results from index cases, and 72,052 SQ-PCR results of HREC. High viral load was observed more frequently among recent cases, symptomatic cases, cases over 25 years of age, and those not recently vaccinated (&amp;gt;90 days). The vaccine effectiveness (VE) of the primary schedule in the first 30 days after vaccination was estimated at 47.3% (95%CI 40.8-53.2) during the Delta variant period. A high viral load in index cases was associated with an increased test positivity in HREC (OR 2.7, 95%CI 2.62-2.79) and, among those testing positive, an increased likelihood of a high viral load (OR 2.84, 95%CI 2.53-3.19).&lt;/p&gt;
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