Are hospitalization and emergency visit rates higher after mRNA boosters compared with protein-based boosters across pediatric, adult, and elderly groups?
Executive summary
Available studies and public-health reviews show mRNA boosters reduce hospitalizations and emergency visits compared with being unboosted, particularly in older adults; head‑to‑head comparisons between mRNA and the protein (Novavax) booster across children, adults and the elderly are limited in current public reports and pooled analyses (notably, pooled mRNA effectiveness against hospitalization in ≥65-year-olds was ~56%) [1]. Guidance and surveillance summaries emphasize mRNA boosters’ demonstrated reductions in hospital/ED use, and while protein vaccines are authorized and effective, direct real‑world, age‑stratified hospitalization/ED comparisons of mRNA vs protein boosters are not clearly reported in the sources provided [1] [2] [3].
1. What the big studies say about boosters and hospitalizations: mRNA is protective
Multiple reviews and cohort studies cited in peer‑reviewed syntheses report that updated mRNA boosters substantially lowered the risk of hospitalization among older adults — for example, pooled vaccine effectiveness of XBB1.5‑adapted mRNA boosters against hospitalization in adults ≥65 was 56% (95% CI, 51–60) in NEJM’s 2025 evidence review [1]. CDC and IVY Network analyses from earlier booster generations also found large relative benefits against hospitalization after bivalent mRNA boosters (relative VE up to ~73% vs unboosted or monovalent‑only groups in older adults) [4] [5]. These sources consistently portray mRNA boosters as reducing serious clinical outcomes, including emergency visits and hospital admissions among adults and especially the elderly [1] [6].
2. Protein (Novavax) is effective but direct comparative data are sparse
Clinical-trial data and authorization summaries describe Novavax’s protein subunit vaccine as effective — with initial trial efficacy near 90% in earlier phases and later authorization for use alongside mRNA options — but the sources here do not provide large, age‑stratified real‑world hospitalization or ED visit comparisons directly pitting protein boosters against mRNA boosters [2] [3]. Yale Medicine and CDC materials note Novavax is an available non‑mRNA option for certain age groups, but neither provides robust head‑to‑head hospitalization/ED outcome rates by age cohort in routine care settings [2] [7].
3. Mixed pooled analyses and limitations: combining platforms blunts signals
The NEJM evidence review indicates studies that combined recipients of mRNA and protein vaccines generally reported lower vaccine effectiveness estimates (21–47%) than studies solely of mRNA recipients — which suggests pooling different platforms can dilute apparent effectiveness and complicate interpretation when trying to compare platforms across ages [1]. That underscores a methodological limitation: many real‑world analyses aggregate platforms or lack power to stratify by both vaccine platform and fine age bands [1].
4. Age matters: elderly show the clearest benefit; pediatric data are thinner
Across the sources, the clearest, most consistent signal of reduced hospitalization following boosters is in adults ≥65, where both mRNA VE estimates and public‑health recommendations emphasize benefit [1] [5]. For children and younger adults, the sources note that boosters reduce urgent care/ED visits and severe outcomes in broader surveillance summaries but do not supply robust, comparative rates across platforms by pediatric, adult and elderly strata [6] [7]. In short: strong evidence for elderly benefit; pediatric head‑to‑head platform comparisons are not found in current reporting [1] [6].
5. What journalists and clinicians should flag: data gaps and potential agendas
Available reporting emphasizes mRNA boosters because they have been most widely used and studied; Novavax’s later rollout means fewer large real‑world comparisons so far [2] [3]. Guidance documents and reviews may implicitly favor mRNA findings because of sample size and surveillance availability; absence of evidence for a platform comparison in these sources should not be read as evidence of no difference — the literature simply lacks granular head‑to‑head hospitalization/ED outcome data across all age groups in the cited reports [1] [3].
6. Bottom line and next steps for readers and reporters
The evidence in these sources shows mRNA boosters substantially reduce hospitalizations and emergency visits, particularly among older adults [1] [4]. Direct, age‑stratified comparisons between mRNA and protein boosters for hospitalization/ED visit rates are not detailed in the materials provided; obtaining definitive answers requires head‑to‑head real‑world effectiveness studies or large registries that stratify by vaccine platform and age (available sources do not mention such studies) [1] [2]. Reporters should press agencies and manufacturers for stratified VE and safety data and caution against overinterpreting pooled analyses that combine platforms [1].