COVID-19 Vaccines for Optimizing Immunity in the Upper Respiratory Tract

Abstract

Rapid development and deployment of vaccines greatly reduced mortality and morbidity during the COVID-19 pandemic. The most widely used COVID-19 vaccines approved by national regulatory authorities require intramuscular administration. SARS-CoV-2 initially infects the upper respiratory tract, where the infection can be eliminated with little or no symptoms by an effective immune response. Failure to eliminate SARS-CoV-2 in the upper respiratory tract results in lower respiratory tract infections that can lead to severe disease and death. Presently used intramuscularly administered COVID-19 vaccines are effective in reducing severe disease and mortality, but are not entirely able to prevent asymptomatic and mild infections as well as person-to-person transmission of the virus. Individual and population differences also influence susceptibility to infection and the propensity to develop severe disease. This article provides a perspective on the nature and the mode of delivery of COVID-19 vaccines that can optimize protective immunity in the upper respiratory tract to reduce infections and virus transmission as well as severe disease.

Keywords: COVID-19; COVID-19 vaccines; SARS-CoV-2; adaptive immunity to COVID-19; clinical vaccine trials; innate immunity to COVID-19; mucosal vaccines; nasal vaccines; upper respiratory tract immunity; vaccine safety.

Figure 1

Infectivity and immunity of SARS-CoV-2 in the URT. Modified from reference [10] with permission under the creative commons attribution (CC BY) license.