Trying to Block SARS-CoV-2 Transmission With Intranasal Vaccines
Rita Rubin
Abstract
urrently available COVID-19 vaccines are highly effective at reducing symptom severity, but they don't appear to prevent SARS-CoV-2 from gaining a toehold in the nose.Ensconced there, the virus can stealthily replicate and then, expelled by coughing or sneezing, go on to infect others.The vaccines, all administered as intramuscular injections, induce circulating antibodies in the blood but not mucosal antibodies in the lining of the nose."It's actually very hard to protect the upper respiratory tract with these [injected] systemic vaccines," Vincent Munster, PhD, chief of the Virus Ecology Section of the National Institute of Allergy and Infectious Diseases (NIAID) Rocky Mountain Laboratories, said in an interview.But what if a COVID-19 vaccine could be sprayed or squirted into the nose?Could such a vaccine induce an immune response in the nasal mucosa, thus stopping SARS-CoV-2 from hitching a ride and spreading?That's the goal of Munster and other scientists in a handful of countries who've been investigating intranasal COVID-19 vaccine candidates.Tests in animal models have looked promising, and phase 1 clinical trials in healthy, COVID-19 vaccine-naive individuals are underway."We think intranasal vaccines are important because they have the potential to block transmission," unlike the available injected vaccines, said Martin Moore, PhD, the CEO and cofounder of Meissa Vaccines in Redwood City, California, which has launched a phase 1 trial of its intranasal vaccine.Studies suggest that individuals who receive injected COVID-19 vaccines may be protected against serious illness from SARS-CoV-2 but can still become infected and spread the virus.For example, research by Munster and coauthors found that the intramuscular Oxford/AstraZeneca vaccine, which isn't authorized in the US, protected rhesus monkeys exposed to SARS-CoV-2 against pneumonia but didn't reduce viral shedding from their upper respiratory tract.And in the 469 cases identified in this past July's COVID-19 outbreak in Provincetown,