Neutralization against Omicron SARS-CoV-2 from previous non-Omicron infection

Area of Science:

• Virology
• Immunology
• Infectious Diseases

Background:

• The emergence of the Omicron variant of SARS-CoV-2 necessitates an understanding of cross-protection from prior non-Omicron infections.
• Assessing the effectiveness of existing immunity against new variants is crucial for public health strategies.

Purpose of the Study:

• To quantify the neutralization capacity of serum from individuals infected with non-Omicron SARS-CoV-2 against the Omicron variant.
• To evaluate the impact of time (1 and 6 months post-infection) on this cross-neutralization.

Main Methods:

• Development of a high-throughput neutralization assay using an engineered Omicron spike gene in a SARS-CoV-2 backbone (USA-WA1/2020).
• Measurement of neutralization titers in patient sera collected 1 and 6 months after non-Omicron SARS-CoV-2 infection.
• Comparison of neutralization titers against the original USA-WA1/2020 strain and the Omicron-spike variant.

Main Results:

• Neutralization titers against USA-WA1/2020 decreased significantly from 1 to 6 months post-infection (601 to 142, a 4.2-fold reduction).
• Neutralization titers against the Omicron-spike variant remained consistently low at both 1 month (38) and 6 months (32) post-infection.
• Titers against Omicron were substantially lower than against USA-WA1/2020, being 15.8-fold lower at 1 month and 4.4-fold lower at 6 months.

Conclusions:

• Previous infection with non-Omicron SARS-CoV-2 provides limited cross-neutralization against the Omicron variant.
• These findings support the recommendation for vaccination in individuals previously infected with non-Omicron SARS-CoV-2 to bolster protection against Omicron.
• Enhanced immunity through vaccination is vital to mitigate the public health impact of the ongoing Omicron surge.