The rapid evolution of SARS-CoV-2 continues to challenge the efficacy of existing COVID-19 vaccines, necessitating frequent updates to address immune evasion. Regulatory bodies worldwide are now considering and approving new vaccine iterations targeting the JN.1 omicron subvariant and its descendants, including the KP.2 (FLiRT) and KP.3 (FLuQE) variants.
Adapting to Viral Evolution
Initial COVID-19 vaccines targeted the original SARS-CoV-2 strain, with subsequent updates incorporating early omicron subvariants like BA.1 and BA.4/5. The most recent update focused on the XBB.1.5 omicron subvariant. However, the emergence of JN.1 in August 2023, and its subsequent evolution into FLiRT and FLuQE variants, prompted the development of vaccines specifically targeting the JN.1 lineage.
Although JN.1 is no longer dominant, vaccines targeting this lineage are expected to provide good protection against newer subvariants, as FLiRT and FLuQE are descendants of JN.1. The World Health Organization (WHO) and the European Medicines Agency (EMA) recommended the use of vaccines targeting the JN.1 lineage in April 2024, anticipating continued viral evolution from this variant.
Regulatory Approvals and Processes
The United States Food and Drug Administration (FDA) has granted emergency use authorization for a Novavax vaccine targeting JN.1. In the United Kingdom, regulators have approved the JN.1-specific Spikevax from Moderna and Comirnaty from Pfizer. Australia's Therapeutic Goods Administration (TGA) is currently evaluating applications for Spikevax and Comirnaty JN.1 vaccines.
The FDA has also recommended and approved vaccines targeting the KP.2 strain, with Moderna and Pfizer developing KP.2-targeted vaccines. Experts suggest the difference between JN.1 and KP.2 boosters will be minimal, with both providing significantly updated protection compared to XBB vaccines.
Safety and Efficacy
Updated JN.1 vaccines have demonstrated substantially improved immune responses against multiple related sublineages, including KP.2 and KP.3, compared to XBB vaccines. These updates are not expected to alter the well-established safety profile of COVID-19 vaccines, though safety and efficacy will continue to be monitored post-approval.
Vaccine Technologies and Uptake
While Pfizer and Moderna utilize mRNA vaccine technology, Novavax offers an adjuvanted protein-based vaccine, providing an alternative for individuals who cannot or prefer not to receive mRNA vaccines. However, the updated Novavax booster is not yet under consideration by the TGA in Australia.
Despite the availability of updated vaccines, booster uptake remains a challenge. As of August, only 31.8% of Australians aged 75 and older had received a COVID-19 vaccine in the previous six months, despite recommendations for vaccination every six months in this age group. Addressing vaccine hesitancy and streamlining the approval process for updated vaccines are crucial for maximizing protection against evolving SARS-CoV-2 variants.
