mRNA booster vaccination protects aged mice against the SARS-CoV-2 Omicron variant

Area of Science:

• Immunology
• Virology
• Gerontology

Background:

• The SARS-CoV-2 Omicron variant exhibits immune evasion properties, potentially reducing the efficacy of existing vaccine-induced immunity.
• While mRNA vaccine boosters enhance neutralizing antibodies against variants, their specific impact on older adults, a high-risk group for severe COVID-19, requires further investigation.

Purpose of the Study:

• To evaluate the longitudinal effects of mRNA-1273 booster immunization in a murine model across different age groups, including aged mice.
• To assess the efficacy of a booster dose administered over 8 months after primary immunization against the Omicron variant.

Main Methods:

• Longitudinal immunization regimens using mRNA-1273 were administered to mice of varying ages, including aged (21-month-old) mice.
• Humoral and cell-mediated immune responses were analyzed, alongside assessments of protection against Omicron-induced lung infection.
• Correlational analyses were performed to link neutralizing antibody activity with protection.

Main Results:

• Boosting significantly enhanced both humoral and cell-mediated immune responses, demonstrating cross-recognition of the Omicron variant.
• While younger mice showed protection without a booster, aged mice required a booster dose to achieve sterilizing immunity against Omicron-induced lung infection.
• A strong correlation was observed between neutralizing activity against Omicron and protection from infection.

Conclusions:

• Vaccine efficacy against SARS-CoV-2 variants is age-dependent.
• mRNA booster immunizations offer significant potential benefits for protecting vulnerable older populations against emerging variants like Omicron.