SARS-CoV-2 Vaccine Efficacy and Immune Response

SARS-CoV-2 vaccines have transformed the global response to the COVID-19 pandemic by reducing the incidence of severe disease and mortality. Broadly, vaccine candidates employ mRNA, viral-vector or inactivated virus platforms, each eliciting distinct profiles of humoral and cellular immunity. Following vaccination, innate immune activation shapes subsequent B-cell and T-cell responses, leading to the production of neutralising antibodies and the formation of memory lymphocytes. While primary series schemes confer robust protection against original viral strains, immunity wanes over time and may be subverted by emerging variants. Booster doses—whether homologous or heterologous—restore antibody titres and broaden cellular recognition, thereby sustaining defence against infection and severe outcomes. Understanding the interplay between vaccine design, immune memory maintenance and variant evolution is critical to optimising immunisation strategies worldwide.

Research from Nature Portfolio

Studies in older adults have demonstrated that inactivated vaccines afford high protection against severe COVID-19 and death, despite moderate efficacy against infection. Booster doses, in particular, substantially enhance defence against critical illness in populations aged over 60. In another nationwide analysis, individuals who initially received two doses of an inactivated vaccine experienced marked recovery of vaccine effectiveness against Omicron with a heterologous mRNA booster, achieving over 90 percent protection against hospitalisation and death. By contrast, homologous inactivated boosters maintained more modest but still significant shield against severe disease. These real-world findings underscore the value of mix-and-match regimens to counteract waning immunity and variant escape, especially among vulnerable groups.

SARS-CoV-2 Vaccine Efficacy and Immune Response publication trend

The graph below shows the total number of articles in sars-cov-2 vaccine efficacy and immune response across all publications each year (not limited to Nature Index journals).

Technical terms

Neutralising antibody: An antibody that binds to viral surface proteins and prevents host-cell entry, blocking infection.

Memory B cell: A long-lived B lymphocyte that recognises antigen upon re-exposure and rapidly differentiates into antibody-secreting cells.

CD4⁺ T cell: A helper T lymphocyte that orchestrates immune responses by activating B cells and cytotoxic T cells.

Heterologous booster: A booster vaccination using a different vaccine platform from the primary series to broaden immune memory.

Waning immunity: The gradual decline in protective immune responses over time following vaccination or infection.

References

1. Effectiveness of inactivated COVID-19 vaccines among older adults in Shanghai: retrospective cohort study. Nature Communications (2023).
2. Effectiveness of an inactivated Covid-19 vaccine with homologous and heterologous boosters against Omicron in Brazil. Nature Communications (2022).
3. Comparing T- and B-cell responses to COVID-19 vaccines across varied immune backgrounds. Signal Transduction and Targeted Therapy (2023).
4. Real-world effectiveness and factors associated with effectiveness of inactivated SARS-CoV-2 vaccines: a systematic review and meta-regression analysis. BMC Medicine (2023).
5. Characterizing the cellular and molecular variabilities of peripheral immune cells in healthy recipients of BBIBP-CorV inactivated SARS-CoV-2 vaccine by single-cell RNA sequencing. Emerging Microbes & Infections (2023).