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. 2023 Jan 11;19(1):2153532. doi: 10.1080/21645515.2022.2153532

Table 3.

PubMed literature search criteria and results.

Search terms

  • COVID-19 AND vaccine AND booster AND mRNA

  • Limited to English language articles
Publication period

  • 1 January 2021, to 29 June 2022
Search results

  • 595 articles selected
Inclusion criteria

  • Studies describing heterologous vaccine regimens

  • Studies describing ≥1 mRNA-based vaccine
Exclusion criteria

  • Review articles

  • Studies of specific populations (such as immunocompromised individuals)

  • Articles not peer-reviewed*

  • Studies describing non-mRNA-based vaccines only

  • Observational studies of small populations (~<100,000 individuals)

  • Observational studies of data before December 2021
Articles extracted

  • 16 articles (15 studies)
Studies identified

  • 8 clinical studies

  • 7 observational studies
Additional studies included†

  • 3 clinical studies

  • 1 observational study

*Except for preprint articles and one study from the Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention.

†Identified outside the PubMed search from ClinicalTrials.gov, mRNA-based vaccine pipelines, and related searches.