![\"\"](\"https:\/\/www.merckvaccines.com\/varivax\/wp-content\/uploads\/sites\/81\/2025\/10\/VARIVAX_4_Clinical-Data_hero_banner_1128px_v5@2x.png?w=1920\")
2 doses of VARIVAX\u00ae (Varicella Virus Vaccine Live) administered subcutaneously demonstrated 98% estimated vaccine efficacy<\/strong> against the varicella virus in children<\/strong><\/h1><\/p>
\n<\/p>\n<\/div>
<\/div><\/div><\/div><\/div><\/div><\/div>\n\n\n\n\n<\/div>\n\n\n\n\nThe estimated vaccine efficacy for VARIVAX administered subcutaneously for the 10-year observation period:<\/h2><\/div>\n\n\n\n<\/div>\n\n\n\n\n\n\n![\"1](\"https:\/\/www.merckvaccines.com\/varivax\/wp-content\/uploads\/sites\/81\/2025\/10\/Varivax_Efficacy_Doses-1st_2nd_Doses_GRAPHIC_v2_bcf623.svg\" "\\"\\"")
![\"1](\"https:\/\/www.merckvaccines.com\/varivax\/wp-content\/uploads\/sites\/81\/2025\/10\/Varivax_Efficacy_Doses-1st_2nd_Doses_GRAPHIC_v2.svg\" "\\"\\"")
<\/figure><\/div><\/div>\n<\/div>\n\n\n\n\n![\"3.4Xa](\"https:\/\/www.merckvaccines.com\/varivax\/wp-content\/uploads\/sites\/81\/2023\/07\/varivax-efficacy-doses-risk_v3.png?w=300\" "\\"\\"")
<\/figure><\/div>\n\n\n\nof developing varicella >42 days<\/span> postvaccination with a 2-dose<\/span> regimen vs a 1-dose<\/span> regimen over a 10-year<\/span> observation period.<\/h3><\/div>\n\n\n\n<\/div>\n\n\n\na<\/sup>2.2% with 2 doses vs 7.5% with 1 dose.<\/span><\/p>\n<\/div>\n<\/div>\n\n\n\nSubcutaneous administration<\/strong><\/h2><\/div>\n\n\n\nStudy design<\/strong><\/h3><\/div>\n\n\n\nIn a clinical trial, a total of 2,216 children 12 months to 12 years of age with a negative history of varicella were randomized to receive either 1 dose of VARIVAX or 2 doses of VARIVAX given 3 months apart. Subjects were actively followed for varicella, any varicella-like illness, or herpes zoster and any exposures to varicella or herpes zoster on an annual basis for 10 years after vaccination. Persistence of varicella-zoster virus antibody was measured annually for 9 years.<\/p><\/div><\/div>\n\n\n\n
<\/div>\n\n\n\n\n
\n\n\n\nIM administration<\/strong><\/h2><\/div>\n\n\n\nStudy design<\/strong><\/h3><\/div>\n\n\n\nIn an open label clinical trial (NCT00432523), 752 children 12 through 18 months of age received VARIVAX either intramuscularly (n=374) or subcutaneously (n=378), concomitantly with M-M-R\u00ae<\/sup>Il<\/sub> (Measles, Mumps, and Rubella Virus Vaccine Live). Ninety-five percent of enrolled children were seronegative to varicella virus at baseline.<\/p><\/div><\/div>\n\n\n\n<\/div>\n\n\n\nPrespecified Primary Analysis Results<\/h3><\/div>\n\n\n\nIn the prespecified primary analysis, seroresponse rates to varicella virus were noninferior in the intramuscular group compared to the subcutaneous group (the lower bound of the 95% CI for the difference in seroresponse rates [intramuscular group minus subcutaneous group] was \u2265-10%). The proportions of children achieving antibody titers above the seroresponse thresholds for varicella virus were 88.4% (95% CI: 84.5, 91.6) of children in the intramuscular group and 85.5% (95% Cl: 81.3, 89.0) of children in the subcutaneous group.<\/p><\/div><\/div>\n\n\n\n\n
- Antibody responses to varicella virus were measured by gpELISA using sera obtained 6 weeks postvaccination.<\/li>
- Seroresponse rate was defined as the percentage of initially seronegative children who achieved antibody titers above the seroresponse threshold for the assay 6 weeks postvaccination.<\/li>
- The seroresponse threshold was defined as 5 gpELISA units for anti-varicella virus antibodies.<\/li><\/ul><\/div>\n","protected":false},"excerpt":{"rendered":"
a2.2% with 2 doses vs 7.5% with 1 dose. In a clinical trial, a total of 2,216 children 12 months to 12…<\/p>\n","protected":false},"author":703,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_trash_the_other_posts":false,"editor_notices":[],"footnotes":""},"ga4_page_audience":[],"ga4_page_birn_id":[],"ga4_page_branding":[224],"ga4_page_businessunit":[232],"ga4_page_campaign":[],"ga4_page_content_purpose":[251],"ga4_page_customer_journey_stage":[292],"ga4_page_customer_specialty":[338],"ga4_page_experience":[],"ga4_page_indication":[495],"ga4_page_material_intent":[497],"ga4_page_product":[688],"ga4_page_region":[794],"ga4_page_therapeuticarea":[846],"class_list":["post-181","page","type-page","status-publish"],"yoast_head":"\n
Vaccine Efficacy Data for VARIVAX\u00ae (Varicella Virus Vaccine Live)<\/title>\n<meta name=\"description\" content=\"Learn about the vaccine efficacy of VARIVAX\u00ae (Varicella Virus Vaccine Live), and how a 2-dose vaccine regimen may help lower the risk of infection.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Vaccine Efficacy Data for VARIVAX\u00ae (Varicella Virus Vaccine Live)\" \/>\n<meta property=\"og:description\" content=\"Learn about the vaccine efficacy of VARIVAX\u00ae (Varicella Virus Vaccine Live), and how a 2-dose vaccine regimen may help lower the risk of infection.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/\" 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infection.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/","og_locale":"en_US","og_type":"article","og_title":"Vaccine Efficacy Data for VARIVAX\u00ae (Varicella Virus Vaccine Live)","og_description":"Learn about the vaccine efficacy of VARIVAX\u00ae (Varicella Virus Vaccine Live), and how a 2-dose vaccine regimen may help lower the risk of infection.","og_url":"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/","og_site_name":"mv-varivax","article_modified_time":"2025-10-28T10:51:33+00:00","og_image":[{"url":"https:\/\/www.merckvaccines.com\/varivax\/wp-content\/uploads\/sites\/81\/2025\/10\/VARIVAX_4_Clinical-Data_hero_banner_1128px_v5@2x.png?w=1920"}],"twitter_card":"summary_large_image","twitter_misc":{"Est. reading time":"3 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infection.","breadcrumb":{"@id":"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.merckvaccines.com\/varivax\/efficacy\/"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/#primaryimage","url":"https:\/\/www.merckvaccines.com\/varivax\/wp-content\/uploads\/sites\/81\/2025\/10\/VARIVAX_4_Clinical-Data_hero_banner_1128px_v5@2x.png","contentUrl":"https:\/\/www.merckvaccines.com\/varivax\/wp-content\/uploads\/sites\/81\/2025\/10\/VARIVAX_4_Clinical-Data_hero_banner_1128px_v5@2x.png","width":2257,"height":485},{"@type":"BreadcrumbList","@id":"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.merckvaccines.com\/varivax\/"},{"@type":"ListItem","position":2,"name":"Clinical 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<\/p>\n<\/div>
The estimated vaccine efficacy for VARIVAX administered subcutaneously for the 10-year observation period:<\/h2><\/div>\n\n\n\n<\/div>\n\n\n\n\n\n\n<\/figure><\/div><\/div>\n<\/div>\n\n\n\n\n<\/figure><\/div>\n\n\n\nof developing varicella >42 days<\/span> postvaccination with a 2-dose<\/span> regimen vs a 1-dose<\/span> regimen over a 10-year<\/span> observation period.<\/h3><\/div>\n\n\n\n<\/div>\n\n\n\na<\/sup>2.2% with 2 doses vs 7.5% with 1 dose.<\/span><\/p>\n<\/div>\n<\/div>\n\n\n\nSubcutaneous administration<\/strong><\/h2><\/div>\n\n\n\nStudy design<\/strong><\/h3><\/div>\n\n\n\nIn a clinical trial, a total of 2,216 children 12 months to 12 years of age with a negative history of varicella were randomized to receive either 1 dose of VARIVAX or 2 doses of VARIVAX given 3 months apart. Subjects were actively followed for varicella, any varicella-like illness, or herpes zoster and any exposures to varicella or herpes zoster on an annual basis for 10 years after vaccination. Persistence of varicella-zoster virus antibody was measured annually for 9 years.<\/p><\/div><\/div>\n\n\n\n
<\/div>\n\n\n\n\n
\n\n\n\nIM administration<\/strong><\/h2><\/div>\n\n\n\nStudy design<\/strong><\/h3><\/div>\n\n\n\nIn an open label clinical trial (NCT00432523), 752 children 12 through 18 months of age received VARIVAX either intramuscularly (n=374) or subcutaneously (n=378), concomitantly with M-M-R\u00ae<\/sup>Il<\/sub> (Measles, Mumps, and Rubella Virus Vaccine Live). Ninety-five percent of enrolled children were seronegative to varicella virus at baseline.<\/p><\/div><\/div>\n\n\n\n<\/div>\n\n\n\nPrespecified Primary Analysis Results<\/h3><\/div>\n\n\n\nIn the prespecified primary analysis, seroresponse rates to varicella virus were noninferior in the intramuscular group compared to the subcutaneous group (the lower bound of the 95% CI for the difference in seroresponse rates [intramuscular group minus subcutaneous group] was \u2265-10%). The proportions of children achieving antibody titers above the seroresponse thresholds for varicella virus were 88.4% (95% CI: 84.5, 91.6) of children in the intramuscular group and 85.5% (95% Cl: 81.3, 89.0) of children in the subcutaneous group.<\/p><\/div><\/div>\n\n\n\n\n
- Antibody responses to varicella virus were measured by gpELISA using sera obtained 6 weeks postvaccination.<\/li>
- Seroresponse rate was defined as the percentage of initially seronegative children who achieved antibody titers above the seroresponse threshold for the assay 6 weeks postvaccination.<\/li>
- The seroresponse threshold was defined as 5 gpELISA units for anti-varicella virus antibodies.<\/li><\/ul><\/div>\n","protected":false},"excerpt":{"rendered":"
a2.2% with 2 doses vs 7.5% with 1 dose. In a clinical trial, a total of 2,216 children 12 months to 12…<\/p>\n","protected":false},"author":703,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_trash_the_other_posts":false,"editor_notices":[],"footnotes":""},"ga4_page_audience":[],"ga4_page_birn_id":[],"ga4_page_branding":[224],"ga4_page_businessunit":[232],"ga4_page_campaign":[],"ga4_page_content_purpose":[251],"ga4_page_customer_journey_stage":[292],"ga4_page_customer_specialty":[338],"ga4_page_experience":[],"ga4_page_indication":[495],"ga4_page_material_intent":[497],"ga4_page_product":[688],"ga4_page_region":[794],"ga4_page_therapeuticarea":[846],"class_list":["post-181","page","type-page","status-publish"],"yoast_head":"\n
Vaccine Efficacy Data for VARIVAX\u00ae (Varicella Virus Vaccine Live)<\/title>\n<meta name=\"description\" content=\"Learn about the vaccine efficacy of VARIVAX\u00ae (Varicella Virus Vaccine Live), and how a 2-dose vaccine regimen may help lower the risk of infection.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Vaccine Efficacy Data for VARIVAX\u00ae (Varicella Virus Vaccine Live)\" \/>\n<meta property=\"og:description\" content=\"Learn about the vaccine efficacy of VARIVAX\u00ae (Varicella Virus Vaccine Live), and how a 2-dose vaccine regimen may help lower the risk of infection.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/\" 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infection.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/","og_locale":"en_US","og_type":"article","og_title":"Vaccine Efficacy Data for VARIVAX\u00ae (Varicella Virus Vaccine Live)","og_description":"Learn about the vaccine efficacy of VARIVAX\u00ae (Varicella Virus Vaccine Live), and how a 2-dose vaccine regimen may help lower the risk of infection.","og_url":"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/","og_site_name":"mv-varivax","article_modified_time":"2025-10-28T10:51:33+00:00","og_image":[{"url":"https:\/\/www.merckvaccines.com\/varivax\/wp-content\/uploads\/sites\/81\/2025\/10\/VARIVAX_4_Clinical-Data_hero_banner_1128px_v5@2x.png?w=1920"}],"twitter_card":"summary_large_image","twitter_misc":{"Est. reading time":"3 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<\/figure><\/div><\/div>\n<\/div>\n\n\n\n<\/figure><\/div>\n\n\n\nof developing varicella >42 days<\/span> postvaccination with a 2-dose<\/span> regimen vs a 1-dose<\/span> regimen over a 10-year<\/span> observation period.<\/h3><\/div>\n\n\n\n<\/div>\n\n\n\na<\/sup>2.2% with 2 doses vs 7.5% with 1 dose.<\/span><\/p>\n<\/div>\n<\/div>\n\n\n\nSubcutaneous administration<\/strong><\/h2><\/div>\n\n\n\nStudy design<\/strong><\/h3><\/div>\n\n\n\nIn a clinical trial, a total of 2,216 children 12 months to 12 years of age with a negative history of varicella were randomized to receive either 1 dose of VARIVAX or 2 doses of VARIVAX given 3 months apart. Subjects were actively followed for varicella, any varicella-like illness, or herpes zoster and any exposures to varicella or herpes zoster on an annual basis for 10 years after vaccination. Persistence of varicella-zoster virus antibody was measured annually for 9 years.<\/p><\/div><\/div>\n\n\n\n
<\/div>\n\n\n\n\n
\n\n\n\nIM administration<\/strong><\/h2><\/div>\n\n\n\nStudy design<\/strong><\/h3><\/div>\n\n\n\nIn an open label clinical trial (NCT00432523), 752 children 12 through 18 months of age received VARIVAX either intramuscularly (n=374) or subcutaneously (n=378), concomitantly with M-M-R\u00ae<\/sup>Il<\/sub> (Measles, Mumps, and Rubella Virus Vaccine Live). Ninety-five percent of enrolled children were seronegative to varicella virus at baseline.<\/p><\/div><\/div>\n\n\n\n<\/div>\n\n\n\nPrespecified Primary Analysis Results<\/h3><\/div>\n\n\n\nIn the prespecified primary analysis, seroresponse rates to varicella virus were noninferior in the intramuscular group compared to the subcutaneous group (the lower bound of the 95% CI for the difference in seroresponse rates [intramuscular group minus subcutaneous group] was \u2265-10%). The proportions of children achieving antibody titers above the seroresponse thresholds for varicella virus were 88.4% (95% CI: 84.5, 91.6) of children in the intramuscular group and 85.5% (95% Cl: 81.3, 89.0) of children in the subcutaneous group.<\/p><\/div><\/div>\n\n\n\n\n
- Antibody responses to varicella virus were measured by gpELISA using sera obtained 6 weeks postvaccination.<\/li>
- Seroresponse rate was defined as the percentage of initially seronegative children who achieved antibody titers above the seroresponse threshold for the assay 6 weeks postvaccination.<\/li>
- The seroresponse threshold was defined as 5 gpELISA units for anti-varicella virus antibodies.<\/li><\/ul><\/div>\n","protected":false},"excerpt":{"rendered":"
a2.2% with 2 doses vs 7.5% with 1 dose. In a clinical trial, a total of 2,216 children 12 months to 12…<\/p>\n","protected":false},"author":703,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_trash_the_other_posts":false,"editor_notices":[],"footnotes":""},"ga4_page_audience":[],"ga4_page_birn_id":[],"ga4_page_branding":[224],"ga4_page_businessunit":[232],"ga4_page_campaign":[],"ga4_page_content_purpose":[251],"ga4_page_customer_journey_stage":[292],"ga4_page_customer_specialty":[338],"ga4_page_experience":[],"ga4_page_indication":[495],"ga4_page_material_intent":[497],"ga4_page_product":[688],"ga4_page_region":[794],"ga4_page_therapeuticarea":[846],"class_list":["post-181","page","type-page","status-publish"],"yoast_head":"\n
Vaccine Efficacy Data for VARIVAX\u00ae (Varicella Virus Vaccine Live)<\/title>\n<meta name=\"description\" content=\"Learn about the vaccine efficacy of VARIVAX\u00ae (Varicella Virus Vaccine Live), and how a 2-dose vaccine regimen may help lower the risk of infection.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Vaccine Efficacy Data for VARIVAX\u00ae (Varicella Virus Vaccine Live)\" \/>\n<meta property=\"og:description\" content=\"Learn about the vaccine efficacy of VARIVAX\u00ae (Varicella Virus Vaccine Live), and how a 2-dose vaccine regimen may help lower the risk of infection.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.merckvaccines.com\/varivax\/efficacy\/\" 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a<\/sup>2.2% with 2 doses vs 7.5% with 1 dose.<\/span><\/p>\n<\/div>\n<\/div>\n\n\n\n In a clinical trial, a total of 2,216 children 12 months to 12 years of age with a negative history of varicella were randomized to receive either 1 dose of VARIVAX or 2 doses of VARIVAX given 3 months apart. Subjects were actively followed for varicella, any varicella-like illness, or herpes zoster and any exposures to varicella or herpes zoster on an annual basis for 10 years after vaccination. Persistence of varicella-zoster virus antibody was measured annually for 9 years.<\/p><\/div><\/div>\n\n\n\n In an open label clinical trial (NCT00432523), 752 children 12 through 18 months of age received VARIVAX either intramuscularly (n=374) or subcutaneously (n=378), concomitantly with M-M-R\u00ae<\/sup>Il<\/sub> (Measles, Mumps, and Rubella Virus Vaccine Live). Ninety-five percent of enrolled children were seronegative to varicella virus at baseline.<\/p><\/div><\/div>\n\n\n\n In the prespecified primary analysis, seroresponse rates to varicella virus were noninferior in the intramuscular group compared to the subcutaneous group (the lower bound of the 95% CI for the difference in seroresponse rates [intramuscular group minus subcutaneous group] was \u2265-10%). The proportions of children achieving antibody titers above the seroresponse thresholds for varicella virus were 88.4% (95% CI: 84.5, 91.6) of children in the intramuscular group and 85.5% (95% Cl: 81.3, 89.0) of children in the subcutaneous group.<\/p><\/div><\/div>\n\n\n\n\n a2.2% with 2 doses vs 7.5% with 1 dose. In a clinical trial, a total of 2,216 children 12 months to 12…<\/p>\n","protected":false},"author":703,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_trash_the_other_posts":false,"editor_notices":[],"footnotes":""},"ga4_page_audience":[],"ga4_page_birn_id":[],"ga4_page_branding":[224],"ga4_page_businessunit":[232],"ga4_page_campaign":[],"ga4_page_content_purpose":[251],"ga4_page_customer_journey_stage":[292],"ga4_page_customer_specialty":[338],"ga4_page_experience":[],"ga4_page_indication":[495],"ga4_page_material_intent":[497],"ga4_page_product":[688],"ga4_page_region":[794],"ga4_page_therapeuticarea":[846],"class_list":["post-181","page","type-page","status-publish"],"yoast_head":"\nSubcutaneous administration<\/strong><\/h2><\/div>\n\n\n\n
Study design<\/strong><\/h3><\/div>\n\n\n\n
\n\n\n\nIM administration<\/strong><\/h2><\/div>\n\n\n\n
Study design<\/strong><\/h3><\/div>\n\n\n\n
Prespecified Primary Analysis Results<\/h3><\/div>\n\n\n\n