Effectiveness of a single COVID-19 mRNA vaccine dose in individuals with prior SARS-CoV-2 infection: a systematic review
Bibliographic record
Abstract
BACKGROUND: Based on high population immunity to SARS-CoV-2 from prior infection, vaccination, or both, in fall 2023, regulatory agencies globally authorized/approved a single mRNA XBB.1.5-adapted vaccine dose for individuals aged ≥5 years regardless of prior vaccination. METHODS: We conducted a systematic review on vaccine effectiveness (VE) of a single COVID-19 mRNA dose in individuals with a history of prior infection compared to individuals who were (i) SARS-CoV-2 naïve, (ii) unvaccinated with prior infection, and (iii) vaccinated with >1 dose with or without prior infection. We searched MEDLINE and Embase for studies published January 2021-October 2023. Data were synthesized following Synthesis Without Meta-Analysis guidelines; bias was assessed using the Newcastle-Ottawa Scale. This study was registered with PROSPERO (CRD42023453257). RESULTS: Eighteen studies were eligible. None of these studies reported bivalent or XBB.1.5-adapted VE, and none reported VE for immunocompromised populations or children aged <5 years. Among those with prior infection, a single mRNA dose increased protection by 8-71% against infection (during Omicron BA.1, BA.4/5, or XBB predominance), 39-67% against symptomatic infection (BA.1, BA.2, or BA.4/5), and 25-60% against hospitalization or hospitalization or death (BA.1). VE of one dose was comparable to two doses among those with prior infection, and higher than following two doses without prior infection. CONCLUSIONS: A single dose of original mRNA COVID-19 vaccine provides similar protection to two doses for immunocompetent individuals aged ≥5 years in the current setting of high pre-existing immunity. This supports current recommendations for one dose to be given in advance of the respiratory season, regardless of history of infection or vaccination, with considerations for additional doses for certain populations including young children, older adults, and the immunocompromised.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.006 | 0.020 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.008 | 0.000 |
| Bibliometrics | 0.002 | 0.006 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".