{"id":1030,"date":"2026-03-05T09:35:58","date_gmt":"2026-03-05T09:35:58","guid":{"rendered":"https:\/\/www.merckvaccines.com\/enflonsia\/?page_id=1030"},"modified":"2026-03-23T08:51:48","modified_gmt":"2026-03-23T08:51:48","slug":"mechanism-of-action","status":"publish","type":"page","link":"https:\/\/www.merckvaccines.com\/enflonsia\/mechanism-of-action\/","title":{"rendered":"Mechanism of action"},"content":{"rendered":"\n<p><\/p>\n\n\n<link rel='stylesheet' id='vivid360-hero-css-css' href='https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/themes\/cex-wpvip-mhh-merck-vivid360-theme-1-12\/blocks\/hero\/css\/style.min.css?ver=1765535927' media='all' \/>\n\n<div id=\"\" class=\"wp-block-vivid360-hero\"><div class=\"vivid360-hero-container align-left align-top ratio-50-50 horizontal desktop text-align-left has-primary-color is-overlay-style is-card-overlay is-white-overlay mobile-is-split-style mobile-split-image-bottom mobile-uses-custom-styles\" style=\"border-width:0;border-style:solid;border-top-left-radius:0;border-top-right-radius:0;border-bottom-right-radius:0;border-bottom-left-radius:0;--minHeight:253px;--mobileMinHeight:288px\"><div class=\"wide_screens hidden\" data-value=\"default\"><\/div><picture><source media=\"(max-width: 767px)\" srcset=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/CAT_Hero-Image_Mobile_MOA_RGB.jpg?w=767\"\/><source media=\"(min-width: 768px) and (max-width:1024px)\" srcset=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/CAT_Hero-Image_Desktop_MOA_RGB.jpg?w=1024\"\/><source media=\"(min-width: 1025px) and (max-width:1440px)\" srcset=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/CAT_Hero-Image_Desktop_MOA_RGB.jpg?w=1440\"\/><img decoding=\"async\" width=\"4512\" height=\"1012\" loading=\"lazy\" data-src=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/CAT_Hero-Image_Desktop_MOA_RGB.jpg?w=1488\" src=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/CAT_Hero-Image_Desktop_MOA_RGB.jpg?w=1488\" alt=\"\" class=\"hero-image\" style=\"--desktop-focal-x:80%;--desktop-focal-y:50%;--mobile-focal-x:50%;--mobile-focal-y:50%;--tablet-focal-x:80%;--tablet-focal-y:50%\"\/><\/picture><div class=\"hero-wrapper\"><div class=\"hero-content\"><h1 style=\"--headlineFontSize:36px;--headlineFontSizeTablet:36px;--headlineFontSizeMobile:24px;--headlineLineHeight:45px;--headlineLineHeightTablet:45px;--headlineLineHeightMobile:30px\" class=\"hero-title fontWeightBold\"><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-primary-color\">ENFLONSIA<sup>TM<\/sup> (clesrovimab-cfor) is designed to rapidly provide antibodies<\/mark><\/h1><p style=\"--contentFontSize:18px;--contentLineHeight:27px;--contentFontSizeMobile:18px;--contentLineHeightMobile:27px\" class=\"hero-description\"><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-primary-color\">to help protect infants entering their first RSV season<\/mark><\/p><div class=\"hero-btn-group\"><\/div><div class=\"hero-caption\"><\/div><\/div><\/div><\/div><div class=\"hero-caption-2desktop\"><\/div><\/div>\n\n\n<link rel='stylesheet' id='vivid360-spacer-css-css' href='https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/themes\/cex-wpvip-mhh-merck-vivid360-theme-1-12\/blocks\/spacer\/css\/style.min.css?ver=1765535928' media='all' \/>\n\n<div style=\"background-color:transparent;height:32px\" class=\"wp-block-vivid360-spacer vivid360-spacer spacer-32\"><\/div>\n\n\n\n<div style=\"background-color:transparent;height:32px\" class=\"wp-block-vivid360-spacer vivid360-spacer spacer-32\"><\/div>\n\n\n<link rel='stylesheet' id='vivid360-row-module-css-css' href='https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/themes\/cex-wpvip-mhh-merck-vivid360-theme-1-12\/blocks\/row\/css\/style.min.css?ver=6.8.5' media='all' \/>\n\n<div style=\"border-width:0px;border-style:;border-radius:0;background-color:#f3efde\" class=\"wp-block-vivid360-row vivid360-row hcp-wide-bg-width regular-bg-width mt-0\"><div class=\"cropped\" id=\"row901b136c-9da8-4385-b3a3-f19819d97bb9\"><div style=\"padding-top:20px;padding-bottom:20px;padding-right:25px;padding-left:25px\" class=\"row-content wide-width hcp-wide-width\">\n<div class=\"wp-block-columns mb-0 mt-0 is-layout-flex wp-container-core-columns-is-layout-9d6595d7 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-vertically-aligned-center mb-0 mt-0 is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:50%\">\n<p class=\"has-text-align-left\">RSV infects cells along the respiratory tract from the nose to the lungs, causing a wide spectrum of respiratory disease, including lower respiratory tract infection<sup>1<\/sup><\/p>\n<\/div>\n\n\n\n<div class=\"column-wrapper _b30f7a52-9364-4514-af88-7e8371ccecbf is-layout-flow wp-block-column-is-layout-flow\"><style>\n\t\t\t\t@media (min-width: 1024px) {\n\t\t\t\t\t.column-wrapper {\n\t\t\t\t\t\tdisplay: contents;\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t\t@media (max-width: 1024px) {\n\t\t\t\t\t#block-b30f7a52-9364-4514-af88-7e8371ccecbf,\n\t\t\t\t\t._b30f7a52-9364-4514-af88-7e8371ccecbf {\n\t\t\t\t\t\tdisplay: contents;\n\t\t\t\t\t\t\n\t\t\t\t\t}\n\t\t\t\t\t.wp-block-columns:not(.is-not-stacked-on-mobile)>.column-wrapper {\n\t\t\t\t\t\tflex-basis: 100% !important;\n\t\t\t\t\t}\n\t\t\t\t\t.column-wrapper .wp-block-column {\n\t\t\t\t\t\torder: inherit;\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t\t@media (max-width: 767px) {\n\t\t\t\t\t#block-b30f7a52-9364-4514-af88-7e8371ccecbf,\n\t\t\t\t\t._b30f7a52-9364-4514-af88-7e8371ccecbf {\n\t\t\t\t\t\tflex-basis: 0 !important;display: unset !important;\n\t\t\t\t\t\t\n\t\t\t\t\t}\n\t\t\t\t\t.column-wrapper .wp-block-column {\n\t\t\t\t\t\torder: inherit;\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t\t<\/style><div class=\"wp-block-column\" style=\"flex-basis:10%\"><\/div><\/div>\n\n\n\n<div class=\"wp-block-column mb-0 mt-0 is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:40%\"><link rel='stylesheet' id='vivid360-image-css-css' href='https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/themes\/cex-wpvip-mhh-merck-vivid360-theme-1-12\/blocks\/image\/css\/style.min.css?ver=1765535927' media='all' \/>\n\n<div class=\"wp-block-vivid360-image\"><div class=\"img-container mb-0 mt-0\"><figure class=\"wp-block-vivid360-image is-style-default has-mobile-image aligncenter size-large is-resized\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_Baby_sketch_v07_pl_AS2_RGB.webp\" alt=\"\" class=\"wp-image-1033  style-noshadow deskHeightAuto  \" width=\"250\" height=\"254\" title=\"\" style=\"height:254px;width:250px\" srcset=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_Baby_sketch_v07_pl_AS2_RGB.webp 500w, https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_Baby_sketch_v07_pl_AS2_RGB.webp?resize=296,300 296w\" sizes=\"auto, (max-width: 250px) 100vw, 250px\" \/><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_Baby_sketch_v07_pl_AS2_RGB.webp\" alt=\"\" class=\"wp-image-1033  style-noshadow mobile-image mobHeightAuto  \" width=\"160\" height=\"127\" title=\"\" style=\"height:127px;width:160px\"\/><\/figure><\/div><\/div>\n<\/div>\n<\/div>\n<\/div><\/div><\/div>\n\n\n\n<div style=\"background-color:transparent;height:32px\" class=\"wp-block-vivid360-spacer vivid360-spacer spacer-32\"><\/div>\n\n\n\n<div style=\"border-width:0px;border-style:;border-radius:0;background-color:#cfeeff\" class=\"wp-block-vivid360-row vivid360-row hcp-wide-bg-width regular-bg-width mb-0\"><div class=\"cropped\" id=\"rowdf479f67-7f9e-487f-8fe9-876e78a7a18c\"><div style=\"padding-top:16px;padding-bottom:20px;padding-right:25px;padding-left:25px\" class=\"row-content wide-width hcp-wide-width\"><link rel='stylesheet' id='vivid360-heading-css-css' href='https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/themes\/cex-wpvip-mhh-merck-vivid360-theme-1-12\/blocks\/heading\/css\/style.min.css?ver=1765535927' media='all' \/>\n\n<div class=\"vivid360-heading default-hcp-fontsize default-hcp-tablet-fontsize\" id=\"a1095d836-40d8-48be-8b10-0aa8fb97ee4d\"><h2 class=\"has-primary-color content-width fontWeightBold mb-0\" style=\"--desktopFontSize:var(--h2FontSizeDesktop);--tabletFontSize:var(--h2FontSizeDesktop);--mobileFontSize:20px;--desktopLineHeightSize:var(--h2LineHeightDesktop);--tabletLineHeightSize:var(--h2LineHeightDesktop);--mobileLineHeightSize:\" id=\"\">Nasal passage<\/h2><\/div>\n\n\n\n<div style=\"background-color:transparent;height:8px\" class=\"wp-block-vivid360-spacer vivid360-spacer spacer-8\"><\/div>\n\n\n\n<div class=\"wp-block-columns mb-0 mt-0 is-layout-flex wp-container-core-columns-is-layout-9d6595d7 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-vertically-aligned-top mb-0 mt-0 is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:50%\">\n<div class=\"wp-block-vivid360-image img-container mb-0 mt-0\"><figure class=\"wp-block-vivid360-image is-style-default has-mobile-image size-large is-resized\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_Nasal-Passage-Graphic@3x.webp\" alt=\"\" class=\"wp-image-1034  style-noshadow deskHeightAuto deskWidthAuto \" width=\"256\" height=\"128\" title=\"\" style=\"height:128px;width:256px\" srcset=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_Nasal-Passage-Graphic@3x.webp 1022w, https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_Nasal-Passage-Graphic@3x.webp?resize=300,151 300w, https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_Nasal-Passage-Graphic@3x.webp?resize=768,386 768w\" sizes=\"auto, (max-width: 256px) 100vw, 256px\" \/><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_Nasal-Passage-Graphic@3x.webp\" alt=\"How ENFLONSIA\u2122 (clesrovimab-cfor) Interacts with RSV in the Nasal Lining Fluid\" class=\"wp-image-1034  style-noshadow mobile-image deskHeightAuto deskWidthAuto \" width=\"1022\" height=\"513\" title=\"\" style=\"height:128px;width:256px\" srcset=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_Nasal-Passage-Graphic@3x.webp 1022w, https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_Nasal-Passage-Graphic@3x.webp?resize=300,151 300w, https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_Nasal-Passage-Graphic@3x.webp?resize=768,386 768w\" sizes=\"auto, (max-width: 1022px) 100vw, 1022px\" \/><\/figure><\/div>\n<\/div>\n\n\n\n<div class=\"wp-block-column is-vertically-aligned-center mb-0 mt-0 is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:50%\">\n<p class=\"has-text-align-left\">ENFLONSIA has been detected in the lining fluid of the nasal mucosal cells in adults\u2014an important point of viral entry into the body.<sup>2,3<\/sup><\/p>\n\n\n\n<div style=\"background-color:transparent;height:16px\" class=\"wp-block-vivid360-spacer vivid360-spacer spacer-16\"><\/div>\n\n\n\n<p class=\"has-text-align-left\">RSV-neutralizing antibody titers in serum were estimated to be <strong>~7x higher than baseline levels at 4 hours <\/strong>following administration<\/p>\n<\/div>\n<\/div>\n<\/div><\/div><\/div>\n\n\n\n<div style=\"background-color:transparent;height:32px\" class=\"wp-block-vivid360-spacer vivid360-spacer spacer-32\"><\/div>\n\n\n\n<div style=\"border-width:0px;border-style:;border-radius:0;background-color:#cfeeff\" class=\"wp-block-vivid360-row vivid360-row hcp-wide-bg-width regular-bg-width mb-0\"><div class=\"cropped\" id=\"row5a9c6b4f-6c3a-4364-8a36-b62b791c7645\"><div style=\"padding-top:16px;padding-bottom:20px;padding-right:25px;padding-left:25px\" class=\"row-content wide-width hcp-wide-width\">\n<div class=\"vivid360-heading default-hcp-fontsize default-hcp-tablet-fontsize\" id=\"a461b1c74-dc62-4c2f-b93a-ffe38d84fdb9\"><h2 class=\"has-primary-color content-width fontWeightBold mb-0\" style=\"--desktopFontSize:var(--h2FontSizeDesktop);--tabletFontSize:var(--h2FontSizeDesktop);--mobileFontSize:20px;--desktopLineHeightSize:var(--h2LineHeightDesktop);--tabletLineHeightSize:var(--h2LineHeightDesktop);--mobileLineHeightSize:\" id=\"\">RSV membrane: a closer look<\/h2><\/div>\n\n\n\n<div style=\"background-color:transparent;height:8px\" class=\"wp-block-vivid360-spacer vivid360-spacer spacer-8\"><\/div>\n\n\n\n<div class=\"wp-block-columns mb-0 mt-0 is-layout-flex wp-container-core-columns-is-layout-9d6595d7 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-vertically-aligned-top mb-0 mt-0 is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:50%\">\n<div class=\"wp-block-vivid360-image img-container mb-0 mt-0\"><figure class=\"wp-block-vivid360-image is-style-default has-mobile-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1023\" height=\"606\" src=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_RSV-Membrane-Graphic@3x.webp\" alt=\"\" class=\"wp-image-1035  style-noshadow deskHeightAuto deskWidthAuto \" title=\"\" style=\"height:606px;width:1023px\" srcset=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_RSV-Membrane-Graphic@3x.webp 1023w, https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_RSV-Membrane-Graphic@3x.webp?resize=300,178 300w, https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_RSV-Membrane-Graphic@3x.webp?resize=768,455 768w\" sizes=\"auto, (max-width: 1023px) 100vw, 1023px\" \/><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_RSV-Membrane-Graphic@3x.webp\" alt=\"ENFLONSIA\u2122 (clesrovimab-cfor) Binds to Site IV After Administration\" class=\"wp-image-1035  style-noshadow mobile-image mobHeightAuto mobWidthAuto \" width=\"1023\" height=\"606\" title=\"\" style=\"height:606px;width:1023px\" srcset=\"https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_RSV-Membrane-Graphic@3x.webp 1023w, https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_RSV-Membrane-Graphic@3x.webp?resize=300,178 300w, https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/uploads\/sites\/276\/2026\/03\/MOA_RSV-Membrane-Graphic@3x.webp?resize=768,455 768w\" sizes=\"auto, (max-width: 1023px) 100vw, 1023px\" \/><\/figure><\/div>\n<\/div>\n\n\n\n<div class=\"wp-block-column is-vertically-aligned-center mb-0 mt-0 is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:50%\"><link rel='stylesheet' id='vivid360-list-parent-css-css' href='https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/themes\/cex-wpvip-mhh-merck-vivid360-theme-1-12\/blocks\/list-parent\/css\/style.css?ver=1765535927' media='all' \/>\n\n<div class=\"vivid-block-list2 content-width  \">\n<ul style=\"--listBulletColor:#333\" class=\"list-bullet-color\">\n<li>Binds to antigenic site IV (<strong>highly conserved<\/strong> in 99.8% of strains)<sup>a<\/sup><\/li>\n\n\n\n<li>Fully human mAb modified for <strong>extended serum<\/strong><sup> <\/sup><strong>half-life<\/strong><sup><strong>b<\/strong><\/sup><\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n<p class=\"has-small-font-size\"><sup>a<\/sup>In sequences reported in GenBank database (accessed 4\/2024).<\/p>\n\n\n\n<p class=\"has-small-font-size\"><sup>b<\/sup>Modified with a triple amino acid substitution (YTE) in the Fc region.<\/p>\n<\/div><\/div><\/div>\n\n\n\n<div style=\"background-color:transparent;height:16px\" class=\"wp-block-vivid360-spacer vivid360-spacer spacer-16\"><\/div>\n\n\n\n<p>F protein, fusion protein; IM, intramuscular; RSV, respiratory syncytial virus; Fc, Fragment crystallizable.<\/p>\n\n\n\n<div style=\"background-color:transparent;--desktop-spacer:48px;--mobile-spacer:48px;--tablet-spacer:48px\" class=\"wp-block-vivid360-spacer vivid360-spacer-desktop vivid360-spacer-mobile vivid360-spacer-tablet\"><\/div>\n\n\n\n<div class=\"wp-block-columns is-layout-flex wp-container-core-columns-is-layout-9d6595d7 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\"><link rel='stylesheet' id='vivid360-card-css-css' href='https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/themes\/cex-wpvip-mhh-merck-vivid360-theme-1-12\/blocks\/card\/css\/style.min.css?ver=1773226567' media='all' \/>\n\n<div id=\"\" class=\"wp-block-vivid360-card a02a7bfb7-4571-4aac-9bac-dfc6d1fe5ec0 vivid360-block-card has-text-align-left hasBoxShadow card-horizontal has-dark-text-color full-page-width\" style=\"border-width:0px;border-style:;border-radius:0\"><div class=\"card-media \"><i role=\"img\" aria-label=\"\" aria-hidden=\"true\" class=\"icon-info-outline has-white-color has-primary-background-color\"><\/i><\/div><div class=\"card-content\"><div class=\"card-content-wrap\"><h3 class=\"card-header fontWeightBold\">What is RSV?<\/h3><p class=\"card-link entire-card left\"><a class=\"\" href=\"https:\/\/www.merckvaccines.com\/enflonsia\/burden-of-disease\/\" role=\"button\" style=\"border-radius:4px\" title=\"\" target=\"_self\" rel=\"noopener\" data-design-category=\"link\" data-design-label=\"\" data-design-module=\"element\"><\/a><\/p><\/div><div class=\"\"><div class=\"card-icon-right\"><i role=\"link\" aria-label=\"\" aria-hidden=\"true\" class=\"icon-arrow-right\"><\/i><\/div><\/div><\/div><\/div>\n<\/div>\n\n\n\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<div id=\"\" class=\"wp-block-vivid360-card a3c675b4d-3337-4861-8f5c-14232e445016 vivid360-block-card has-text-align-left hasBoxShadow card-horizontal has-dark-text-color full-page-width\" style=\"border-width:0px;border-style:;border-radius:0\"><div class=\"card-media \"><i role=\"img\" aria-label=\"\" aria-hidden=\"true\" class=\"icon-hand-holding-medical \"><\/i><\/div><div class=\"card-content\"><div class=\"card-content-wrap\"><h3 class=\"card-header fontWeightBold\">Order ENFLONSIA now<\/h3><p class=\"card-link entire-card left\"><a class=\"\" href=\"https:\/\/ordering.merckvaccines.com\/landing-page\" role=\"button\" style=\"border-radius:4px\" title=\"\" target=\"_self\" rel=\"noopener\" data-design-category=\"link\" data-design-label=\"\" data-design-module=\"element\"><\/a><\/p><\/div><div class=\"\"><div class=\"card-icon-right\"><i role=\"link\" aria-label=\"\" aria-hidden=\"true\" class=\"icon-arrow-right\"><\/i><\/div><\/div><\/div><\/div>\n<\/div>\n<\/div>\n\n\n\n<div class=\"vivid360-heading default-hcp-fontsize default-hcp-tablet-fontsize default-hcp-mobile-fontsize\" id=\"a69383c99-80e0-4868-98d6-419161348793\"><h2 class=\"content-width fontWeightRegular\" style=\"--desktopFontSize:var(--h2FontSizeDesktop);--tabletFontSize:var(--h2FontSizeDesktop);--mobileFontSize:var(--h2FontSizeMobile);--desktopLineHeightSize:var(--h2LineHeightDesktop);--tabletLineHeightSize:var(--h2LineHeightDesktop);--mobileLineHeightSize:\" id=\"\"><strong>References:<\/strong><\/h2><\/div>\n\n\n\n<div class=\"vivid-block-list2 content-width  \">\n<ol style=\"--listBulletColor:#333\" class=\"list-bullet-color\">\n<li>Respiratory syncytial virus (RSV). World Health Organization. Published December 19, 2025. Accessed January 6, 2025. https:\/\/www.who.int\/news-room\/fact-sheets\/detail\/respiratory-syncytial-virus-(rsv)#<\/li>\n\n\n\n<li>How RSV spreads. Centers for Disease Control and Prevention. July 8, 2025. Accessed July 24, 2025. https:\/\/www.cdc.gov\/rsv\/causes\/<\/li>\n\n\n\n<li>Phuah JY, Maas BM, Tang A, et al. Quantification of clesrovimab, an investigational, half-life extended, anti-respiratory syncytial virus protein F human monoclonal antibody in the nasal epithelial lining fluid of healthy adults. <em>Biomed Pharmacother<\/em>. 2023;169:115851. doi:10.1016\/j.biopha.2023.115851<\/li>\n<\/ol>\n<\/div>\n\n\n<link rel='stylesheet' id='vivid360-modal-css-css' href='https:\/\/www.merckvaccines.com\/enflonsia\/wp-content\/themes\/cex-wpvip-mhh-merck-vivid360-theme-1-12\/blocks\/modal\/css\/style.min.css?ver=1769466497' media='all' \/>\n\n<div class=\"wp-block-vivid360-modal\"><div><div class=\"vivid360-modal-block-container is-style-passive-modal-two-btn\"><div class=\"vivid360-modal-trigger-container\"><span id=\"inlineTrigger\" role=\"link\" data-design-module=\"modal\" data-design-category=\"link\" class=\"vivid360-modal-trigger vivid360-modal-trigger-hide\">patientSite<\/span><\/div><div class=\"vivid360-modal-container null\"><div class=\"vivid360-modal\" style=\"color:#00857c\"><div 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