<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>27</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Nayema Van den Houte</style></author><author><style face="normal" font="default" size="100%">V Leclercq</style></author><author><style face="normal" font="default" size="100%">Lydia Gisle</style></author><author><style face="normal" font="default" size="100%">Johan Van der Heyden</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Prevalence  of anti-SARS-CoV-2 antibodies in the general population in Belgium : Results of the second data collection (28/09/21-23/02/22)</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">antibodies</style></keyword><keyword><style  face="normal" font="default" size="100%">COVID-19</style></keyword><keyword><style  face="normal" font="default" size="100%">health determinants</style></keyword><keyword><style  face="normal" font="default" size="100%">population-based</style></keyword><keyword><style  face="normal" font="default" size="100%">Seroprevalence</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2022</style></year><pub-dates><date><style  face="normal" font="default" size="100%">21/04/2022</style></date></pub-dates></dates><publisher><style face="normal" font="default" size="100%">Sciensano</style></publisher><pub-location><style face="normal" font="default" size="100%">Brussels, Belgium</style></pub-location><pages><style face="normal" font="default" size="100%">13</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;&lt;u&gt;&lt;strong&gt;KEY FINDINGS&lt;/strong&gt;&lt;/u&gt;&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;Between the last period of wave 1 (14/06-11/07) and the first period of wave 2 (27/09-24/10) the percentage of adults (18 years or older) with anti-SARS-CoV-2 antibodies has increased from 69.5% to 90.4%. This substantial increase is in line with the intensive vaccination campaign during this time period. During the second period of wave 2 (25/10-21/11) the prevalence increased further to 92.9%.&lt;/li&gt;
	&lt;li&gt;Among the fully vaccinated having received the last dose (eventually a booster) in the past 3 months (but more than 2 weeks ago), the prevalence of anti-SARS-CoV-2 antibodies was 97.9% in the first period of wave 2 (27/09-24/10) and 99.1% in the second period (25/10-21/11). Among the fully vaccinated having received the last dose (eventually a booster) longer than 3 months ago, these percentages were respectively 93.8% and 95.7%&lt;/li&gt;
	&lt;li&gt;Among people who had not received any COVID-19 vaccine at all the prevalence of anti-SARS-CoV-2 antibodies increased in wave 2 from 22.5% (27/09-24/10) to 36.5% (25/10-21/11). However, caution is needed to interpret these figures, because in wave 2 the number of unvaccinated people was quite low.&lt;/li&gt;
	&lt;li&gt;Most of those who had a negative test in wave 1 (87.8%) became positive in wave 2. This is mainly explained by the vaccination campaign: 94.8% of these people received a COVID-19 vaccine between their participation in wave 1 and wave 2. Only 9.7% of the unvaccinated people with a negative test in wave 1 became positive in wave 2.&lt;/li&gt;
	&lt;li&gt;In total, 3.1% of those who had anti-SARS-CoV-2-antibodies in wave 1 seroconverted in wave 2. Among the unvaccinated and the partially vaccinated people, the risk of becoming seronegative was 10 times higher than among the fully vaccinated.&lt;/li&gt;
	&lt;li&gt;Among the total study population, older age was associated with a higher risk of not having antibodies in wave 2.&lt;/li&gt;
	&lt;li&gt;Among the fully vaccinated, older people and people with at least one chronic disease were at higher risk of not carrying antibodies. The risk of being seronegative in wave 2 increased significantly as the number of days since the last vaccination advanced. Furthermore, having received at least one dose of mRNA vaccine compared to adenoviral-vectored vaccine reduced the risk of being seronegative by 90%.&lt;/li&gt;
&lt;/ul&gt;
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