This updated Good Practice Statement on the utilization of COVID-19 vaccines containing variants reflects recommendations from the Strategic Advisory Group of Experts (SAGE) on Immunization, as conveyed during its meeting on September 28, 2023.
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In May 2023, the Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) advised a departure from incorporating the ancestral strain in future COVID-19 vaccine formulations. The rationale for adopting a monovalent variant-containing strategy to address current and emerging variants is outlined here.
COVID-19
The revised recommendations from TAG-CO-VAC and this Good Practice Statement amalgamate current evidence on variant-containing COVID-19 vaccines, particularly those featuring XBB. This document includes certain off-label recommendations.
Throughout this document, the terms “primary series” and “initial doses” are used interchangeably, as are “additional doses” and “booster doses.”
Background and Methods
Globally, population-level immunity against SARS-CoV-2 has substantially increased due to widespread immunity derived from COVID-19 vaccines, SARS-CoV-2 infections, or a combination of both (hybrid immunity). Concurrently, marked reductions in severe SARS-CoV-2-related illness and mortality have been observed across all age groups. Consequently, many countries have eased or lifted most public health measures.
In the fourth year of the pandemic, new SARS-CoV-2 subvariants continue to circulate globally, posing ongoing risks of severe disease and death to vulnerable populations. The spike protein of SARSCoV-2 continues to diverge from the ancestral strain.
Following the emergence of Omicron in November 2021, earlier variants (Alpha, Beta, Gamma, and Delta) ceased to circulate in humans. By May 2023, global prevalence was predominantly driven by Omicron subvariants, including XBB.1.5, XBB.1.16, and XBB.1.9. Recently, additional Omicron subvariants such as EG.5 and BA.2.86 have surfaced.
While Omicron and its subvariants have resulted in milder disease compared to the ancestral strain, surges in hospitalizations and deaths have occurred in vulnerable populations due to heightened community transmission and periodic waves of infections.
WHO conducted a swift review of current evidence on XBB variants and monovalent XBB vaccines obtained from scientific publications, preprints, and manufacturer-provided data (1-3). The review encompassed the following topics:
Immune evasion in humans
Variant-adapted vaccines: humoral and cell-mediated immune responses post-vaccination and/or infection in humans and animals
Vaccine effectiveness
Vaccine safety
