Abstract
The novel coronavirus, SARS-CoV-2, which causes COVID-19, has resulted in a pandemic with millions of deaths. To eradicate SARS-CoV-2 and prevent further infections, many vaccine candidates have been developed. These vaccines include not only traditional subunit vaccines and attenuated or inactivated viral vaccines but also nucleic acid and viral vector vaccines. In contrast to the diversity in the platform technology, the delivery of vaccines is limited to intramuscular vaccination. Although intramuscular vaccination is safe and effective, mucosal vaccination could improve the local immune responses that block the spread of pathogens. However, a lack of understanding of mucosal immunity combined with the urgent need for a COVID-19 vaccine has resulted in only intramuscular vaccinations. In this review, we summarize the history of vaccines, current progress in COVID-19 vaccine technology, and the status of intranasal COVID-19 vaccines. Future research should determine the most effective route for vaccine delivery based on the platform and determine the mechanisms that underlie the efficacy of different delivery routes.
Highlights
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel virus that causes coronavirus disease 2019 (COVID-19), is responsible for a pandemic that has resulted in millions of deaths across the globe
The rapid development of vaccine technology has led to several vaccines for COVID-19
Some of the vaccines that have been approved for emergency use include mRNA-1273 (Moderna), AZD1222 (AstraZeneca), and Ad26.COV2.S (J&J/Janssen), which are delivered intramuscularly, and the results of their global use will provide important information on their safety and efficacy
Summary
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel virus that causes coronavirus disease 2019 (COVID-19), is responsible for a pandemic that has resulted in millions of deaths across the globe. There is an urgent need for effective vaccines to prevent COVID-19 and eradicate SARS-CoV-2, and many companies are developing and testing new vaccines. These include traditional vaccines, such as inactivated and attenuated viruses or subunit vaccines, and new RNA, DNA, and viral vector vaccines [1]. Since SARS-CoV-2 infects via the respiratory tract, intranasal vaccination should be effective. While the angiotensin-converting enzyme (ACE2) receptor for SARS-CoV-2 is found throughout the respiratory tract and in the brain, placenta, and gut, the first line of defense against infection is the nasal epithelium [2]. We review recent progress on delivery routes for COVID-19 vaccines and discuss future perspectives
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