Immunogenicity of a single dose mRNA vaccine in SARS-CoV-2 exposed subjects: A systematic review
Journal: South East Asia Journal of Medical Sciences
Article type: Research Article
Published: 2022-09-26
Volume: 6; Issue: 2; Pages: 1-13
ISSN: 2522-7165
Article URL: https://journals.littlebaypublishers.com/article/article-1783008743595-292167227
PDF: https://journals.littlebaypublishers.com/article/article-1783008743595-292167227.pdf
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Authors
- Jagtar Singh
Faculty of Pharmaceutical Sciences, PCTE Group of Institutes, Ludhiana, Punjab, India - Seema Thakur
Faculty of Pharmaceutical Sciences, PCTE Group of Institutes, Ludhiana, Punjab, India
https://orcid.org/0000-0002-7737-8402
Abstract
Background: The novel coronavirus is quickly spreading and mutating, putting the public health and lifestyle in shambles. The development and approval of mRNA vaccines came up as a breakthrough. The breadth of immune response after a single-dose vaccination in the already infected population is discovered for understanding the hybrid immunity and side effects associated with second dose. Administering a single-dose vaccine to the seropositive population can spare the doses for the population at higher risk. 
 Methods: PubMed, Web of Science, Google scholar, medRxiv and Cochrane library were explored to extract the original data on the efficacy of single-dose mRNA vaccines in seropositive subjects. The Cochrane risk of bias tool was used to assess the risk of bias in the studies. 
 Results: 6 studies evaluating the immunogenicity of single-dose mRNA vaccine were incorporated along with some observational studies and literature. These studies present promising evidence for administering only single-dose mRNA vaccine in seropositive subjects, providing biphasic immune response of higher breadth and duration. 
 Limitations: Most studies had a small sample size, did not correlate the results with higher age groups, with potential risk factors and the percentage of individuals who contracted breakthrough infections. 
 Conclusions: Single-dose mRNA vaccine can be immunogenic and protective enough for already seropositive population by increasing the number of Spike protein-specific memory B-cells. Vaccination schedules based on existing anti-body titers in such individuals can spare doses for vulnerable groups, especially when there is limited production and supply of vaccines worldwide.
Keywords
Immunity, SARS-CoV-2, Vaccination, COVID-19, mRNA
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