Persistent B cell memory after SARS-CoV-2 vaccination is functional during breakthrough infections

Area of Science:

• Immunology
• Vaccinology
• Virology

Background:

• Breakthrough SARS-CoV-2 infections in vaccinated individuals are often attributed to waning immunity.
• Serum antibodies are a key indicator of vaccine-induced B cell memory.
• Memory B cells are crucial for sustained protection against pathogens, even as antibody levels decline.

Purpose of the Study:

• To investigate the durability and functionality of BNT162b2 mRNA vaccine-induced B cell memory against SARS-CoV-2.
• To assess B cell memory response at 3, 6, and 9 months post-second dose in healthcare workers (HCWs).

Main Methods:

• Longitudinal study of HCWs vaccinated with BNT162b2 mRNA vaccine.
• Measurement of SARS-CoV-2-specific antibodies and memory B cell responses over time.
• Analysis of B cell memory in HCWs with and without breakthrough infections.

Main Results:

• SARS-CoV-2-specific antibodies showed a physiological decline over 9 months.
• Memory B cells persisted and increased up to 9 months post-vaccination.
• HCWs with breakthrough infections did not exhibit waning immunity; memory B cells rapidly produced antibodies upon infection.
• A rapid production of serum antibodies and salivary anti-Spike IgA was observed within 3-4 days of infection.

Conclusions:

• The BNT162b2 mRNA vaccine induces durable and functional memory B cell responses.
• Memory B cells provide sustained protection against SARS-CoV-2, mitigating severe disease despite antibody decline.
• Breakthrough infections do not indicate a failure of vaccine-induced memory B cells but rather a dynamic immune response.