The Most Effective COVID-19 Vaccine Could Be Intranasal

The pace of vaccine development against COVID-19 will certainly go down as one of the fastest in our history. In less than a year, a number of vaccines have been developed and distributed that  prevent illness from COVID-19. In the U.S. alone, more than 200 million doses of vaccine have been distributed as of April 2021.

These vaccines only prevent illness — they are not designed to halt asymptomatic or other transmission of the disease. Thus, while rates of illness (and hospitalizations and deaths) have dropped in countries where vaccinations are widespread (such as the United States, Israel, and Great Britain) the risks of spreading the virus remain high. The ability of these vaccines to prevent transmission is limited by the vaccine’s targets — intramuscular injections raise the antibody immunoglobulin G (IgG), which triggers antibody and other immune responses to fight the viruses that have already entered the body. Just as this approach does not prevent the virus from entering the body, it doesn’t prevent that active virus from leaving via the airways – the typical route of transmission for SARS-Cov-2.

Other vaccine developers, however, are looking at preventing the coronavirus from being transmitted by focusing on the nose and respiratory tract. An intranasal vaccine would trigger immune responses in the nose, throat and lung mucosa by targeting immunoglobulin A (IgA), antibodies which exist solely in the mucosa. The mucosa acts as a physical barrier to potential pathogens, trapping them before they have a chance to enter the body. Given this, the intranasal vaccine would prevent transmission from exhaled droplets or aerosols, as there would not be virus in the body to exhale.