How have COVID vaccine formulations changed from 2023 to 2024-2025?

Executive Summary — Short, Clear, and Current

From 2023 to the 2024–2025 season, COVID‑19 vaccine compositions moved from formulations centered on the XBB.1.5 Omicron lineage to updated vaccines targeting the JN.1/KP.2 Omicron descendants, with both mRNA and protein‑based adjuvanted products adapted accordingly; regulators and immunization committees formalized those changes in 2024 and continued to refine age‑ and risk‑based recommendations into 2025. Manufacturers (Pfizer‑BioNTech, Moderna, Novavax) released lineage‑updated boosters and new product authorizations, while public health agencies adjusted schedules and clinical guidance, producing some variation across statements about which sublineages are prioritized and which age/risk groups are emphasized ^{[1] [2] [3] [4] [5]}.

1. How the Formula Shift Happened — Variant Tracking Driving Vaccine Updates

Regulatory filings and advisory committee decisions record a clear technical progression: the 2022–2023 and into 2023 formulations emphasized protection against XBB.1.5, but surveillance data showing the rise of new Omicron descendants prompted manufacturers and regulators to update vaccine antigens for the 2024–2025 season to JN.1 lineage and KP.2 subvariants. Public statements and schedule updates list monovalent and lineage‑targeted updates across both mRNA and protein‑based adjuvanted platforms, reflecting the standard influenza‑like approach of matching circulating strains. The change is documented in contemporaneous vaccine schedule and product announcements and is framed as an evolutionary response to viral antigenic drift rather than a change in platform technology (mRNA vs protein) ^{[1] [2] [3]}.

2. Product Approvals and New Players — Moderna, Pfizer, Novavax and Beyond

Between 2024 and 2025 regulatory actions included approvals and authorizations for updated boosters and, in some jurisdictions, new formulations such as Moderna’s mNexspike for people 12 and older and Novavax’s protein vaccine reformulated for JN.1. These approvals reflect manufacturers updating spike antigens to match JN.1/KP.2‑descended lineages and sometimes changing dose or age indications. The documentation shows alignment across multiple manufacturers to the same lineage targets in 2024–2025, while retaining differences in platform (mRNA vs recombinant protein) and age‑labeling that affect clinical rollout and public messaging ^{[6] [5] [1]}.

3. Public‑Health Guidance — ACIP/CDC Shifts and Implementation Nuances

Advisory bodies incorporated the lineage updates into adult immunization schedules and booster recommendations, with ACIP and CDC materials in 2024 listing an “updated 2023–2024 formula” then moving to JN.1‑targeted guidance for 2024–2025. Guidance documents show nuance: some recommendations emphasized shared decision‑making for certain age groups, while others prioritized older adults or people with risk factors for booster receipt. These distinctions produced practical variability in uptake and messaging, as some sources highlight universal recommendations for people 6 months and older while others indicate focused recommendations for higher‑risk cohorts—reflecting a tension between broad public health protection and targeted risk‑based strategies ^{[7] [1] [5]}.

4. Conflicting Signals and Variant Names — Why Different Reports Emphasize Different Sublineages

Analyses across sources show minor—but consequential—differences in how authors name and prioritize sublineages: some reports name KP.2/JN.1 explicitly as the 2024–2025 target, others reference KP.3.1.1 or LP.8.1 in later 2025 commentary. These variations stem from rapidly shifting surveillance data and differing cut‑offs for which descendant lineages are considered “dominant” at the time of regulatory submission versus publication. The result is apparent inconsistency across sources that is a product of timing and genomic surveillance sampling, not necessarily disagreement about the principle of updating vaccines to better match circulating viruses ^{[4] [8] [9]}.

5. What This Means for Patients and Clinicians — Practical Takeaways

For clinicians and patients the core fact is straightforward: vaccines in 2024–2025 are antigen‑updated to reflect JN.1/KP.2 lineage descendants and are available in both mRNA and protein adjuvanted forms; decisions on who should receive which product and when vary by age, risk status, and jurisdictional guidance. Public communications and insurer coverage notes show continued emphasis on protecting older adults and immunocompromised people while enabling broader access through shared decision‑making frameworks. Stakeholders should expect periodic antigenic updates and alignment of product labeling and schedules with surveillance findings as the principal pattern going forward ^{[3] [6] [1]}.