Review of heterologous vaccination in convalescent and infection-naive populations against SARS-CoV-2

This narrative review evaluates the immunological impact of heterologous vaccination, defined as the sequential use of vaccines based on different technological platforms, in convalescent individuals and infection-naïve populations. The scope focuses on comparing these heterologous regimens against standard homologous vaccination schedules to assess their potential as a public health strategy for optimizing hybrid immunity.

The authors synthesize key arguments indicating that heterologous vaccination regimens outperform homologous regimens across three primary domains. Specifically, the review notes an enhancement in the breadth of neutralizing antibodies, a strengthening of cross-protection capabilities, and the establishment of robust immune memory. However, the review does not provide pooled effect sizes, absolute numbers, p-values, or confidence intervals for these outcomes.

The authors acknowledge that specific safety data, including adverse events, serious adverse events, discontinuations, and tolerability, were not reported in the source material. Furthermore, follow-up duration and the primary outcome metric were not reported. Despite these gaps, the review concludes that heterologous vaccination can serve as an active public health strategy to simulate and optimize hybrid immunity, though the certainty of these conclusions is limited by the qualitative nature of the synthesis.