Immunogenicity of JN.1 and KP.2 COVID-19 mRNA vaccines against emerging SARS-CoV-2 variants

Ninaad Lasrado; Annika Rössler; Isabella McConnell; Katherine Molloy; Ritobhas Bhowmik; Christine Happle; Ruoran Guan; Katherine McMahan; Juliana Pereira; Jinyan Liu; Erica Borducchi; Liping Wang; Krishna Shah; Bridget Wixted; Metodi V Stankov; Alexandra Dopfer-Jablonka; Ai-Ris Y Collier; Georg M N Behrens; Dan H Barouch

doi:10.1016/j.vaccine.2025.127997

Immunogenicity of JN.1 and KP.2 COVID-19 mRNA vaccines against emerging SARS-CoV-2 variants

Vaccine. 2026 Jan 1:69:127997. doi: 10.1016/j.vaccine.2025.127997. Epub 2025 Nov 19.

Authors

Ninaad Lasrado¹, Annika Rössler¹, Isabella McConnell¹, Katherine Molloy¹, Ritobhas Bhowmik¹, Christine Happle², Ruoran Guan¹, Katherine McMahan¹, Juliana Pereira¹, Jinyan Liu¹, Erica Borducchi¹, Liping Wang¹, Krishna Shah¹, Bridget Wixted¹, Metodi V Stankov³, Alexandra Dopfer-Jablonka³, Ai-Ris Y Collier¹, Georg M N Behrens⁴, Dan H Barouch⁵

Affiliations

¹ Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
² German Centre for Lung Research (DZL), Hannover BREATH, Hannover, Germany; German Centre for Infection Research (DZIF), Hannover-Braunschweig, Hannover, Germany; Department for Paediatric Pneumology, Hannover Medical School, Hannover, Germany; Department for Rheumatology and Immunology, Hannover Medical School, Hannover, Germany.
³ German Centre for Infection Research (DZIF), Hannover-Braunschweig, Hannover, Germany; Department for Rheumatology and Immunology, Hannover Medical School, Hannover, Germany.
⁴ German Centre for Lung Research (DZL), Hannover BREATH, Hannover, Germany; German Centre for Infection Research (DZIF), Hannover-Braunschweig, Hannover, Germany.
⁵ Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA. Electronic address: dbarouch@bidmc.harvard.edu.

Abstract

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) continues to evolve five years after the initial outbreak. Although mRNA vaccines encoding the JN.1 and KP.2 Spike proteins were authorized in fall 2024, it remains unclear whether vaccine updates will be necessary for variants containing antigenically closely related Spike proteins. In this study, we evaluated the immunogenicity of JN.1 and KP.2 mRNA boosters in participants from Germany and the United States, respectively. Both vaccines induced robust and similar neutralizing antibody responses against JN.1, KP.2, and other globally relevant variants such as LP.8.1.1 and NB.1.8.1. These data suggest that updating the vaccine formulation to closely related strains will likely offer only modest additional benefits against currently circulating variants.

Keywords: Booster; COVID-19; JN.1; KP.2; mRNA.

MeSH terms

Adult
Antibodies, Neutralizing / blood
Antibodies, Neutralizing / immunology
Antibodies, Viral / blood
Antibodies, Viral / immunology
COVID-19 Vaccines* / administration & dosage
COVID-19 Vaccines* / immunology
COVID-19* / immunology
COVID-19* / prevention & control
COVID-19* / virology
Female
Germany
Humans
Immunogenicity, Vaccine*
Male
Middle Aged
SARS-CoV-2* / genetics
SARS-CoV-2* / immunology
Spike Glycoprotein, Coronavirus / genetics
Spike Glycoprotein, Coronavirus / immunology
United States
Vaccines, Synthetic / administration & dosage
Vaccines, Synthetic / immunology
mRNA Vaccines / immunology

Substances

COVID-19 Vaccines
Antibodies, Neutralizing
Antibodies, Viral
Spike Glycoprotein, Coronavirus
mRNA Vaccines
spike protein, SARS-CoV-2
Vaccines, Synthetic

Supplementary concepts

SARS-CoV-2 variants

Grants and funding

U01 CA260476/CA/NCI NIH HHS/United States