Human IgM and IgG Responses to an Inactivated SARS-CoV-2 Vaccine

Area of Science:

• Immunology
• Vaccinology
• Infectious Diseases

Background:

• The COVID-19 pandemic necessitates rapid vaccine development and evaluation.
• Understanding factors influencing vaccine-induced immune responses is crucial for optimizing vaccine efficacy.

Purpose of the Study:

• To assess antibody responses following an inactivated SARS-CoV-2 vaccine in infection-naïve individuals.
• To explore the impact of age and time post-vaccination on antibody levels.

Main Methods:

• A retrospective study of 97 healthy, infection-naïve adults (18-60 years) who received two doses of inactivated SARS-CoV-2 vaccine.
• Serum IgM and IgG antibodies were quantified post-second dose using a commercial assay.
• Seropositivity defined as ≥10 AU/mL.

Main Results:

• High seropositive rate for IgG (74.2%) and low for IgM (3.1%) antibodies after two doses.
• IgG levels were significantly higher than IgM levels (P<0.0001).
• Older recipients (≥42 years) and later detection times (>42 days post-vaccination) showed significantly lower IgG levels.

Conclusions:

• Inactivated SARS-CoV-2 vaccine successfully induces IgG antibody responses in healthy adults.
• Age and time elapsed since the second vaccine dose are significant factors affecting antibody levels.