Current status of mucosal vaccines against SARS-CoV2: a hope for protective immunity

ABSTRACT

Introduction

The current vaccines used to fight against COVID-19 are effective, however the induction of protective immunity is a pending goal required to prevent viral transmission, prevent the generation of new variants, and ultimately eradicate SARS-CoV-2. Mucosal immunization stands as a promising approach to achieve protective immunity against SARS-CoV-2; therefore, it is imperative to innovate the current vaccines by developing mucosal candidates, focusing not only on their ability to prevent severe COVID-19 but to neutralize the virus before invasion of the respiratory system and other mucosal compartments.

Areas covered

This review covers the current advances on the development of anti-COVID-19 mucosal vaccines. Biomedical literature, including PubMed and clinicaltrials.gov website, was analyzed to identify the state of the art for this field. The achievements in preclinical and clinical evaluations are presented and critically analyzed.

Expert opinion

There is a significant advance on the development of mucosal vaccines against SARSCoV-2, which is a promise to increase the efficacy of immunization against this pathogen. Both preclinical and clinical evaluation for several candidates have been performed. The challenges in this road (e.g. low immunogenicity, a reduced number of adjuvants available, and inaccurate dosage) are identified and also critical perspectives for the field are provided.

KEYWORDS:

• Common mucosal immune system
• COVID-19
• lymphocyte homing
• nasal immunization
• oral immunization
• protective immunity variants of concern

Article highlights

• Although many vaccines are available to fight COVID-19, new vaccines capable of achieving protective immunity are required.

• Mucosal immunization is a viable approach to boost vaccinated individuals and achieve protective immunity.

• Several vaccine platforms based on mucosal immunization schemes are under exploration to address such goal, mainly including viral-vectored vaccines and nanocarrier-based vaccines.

• Low immunogenicity, a reduced number of mucosal adjuvants available, dose inaccuracy, and preexisting immunity are among the challenges to be addressed in this field.

• Clinical studies are required to validate the immunogenic properties observed in mice given the substantial differences with the human immune system.

This box summarizes key points contained in the article.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was funded by Consejo Nacional de Ciencia y Tecnología, México, Grant number 321364.