In animal studies that mimic human exposure, a tested oral vaccine against COVID not only protects the host but also reduces the spread of the virus by air to other close contacts.
The study, led by Duke researcher Stephanie N. Langel, PhD, demonstrated the potential of a vaccine against COVID that works through the mucosa to neutralize the SARS-CoV-2 virus, limiting infections and the spread of active virus in airborne particles.
The results are published today in the journal Science Translational Medicine.
“Given that most of the world is under-immunized – and this is especially true for children – the possibility of a vaccinated person with a breakthrough infection can spread COVID to non-immunized family or community members poses a risk to public health.” said Langel. “There will be significant benefits in developing vaccines that not only protect against disease but also reduce the transmission of unvaccinated people.
Langel and colleagues – including teams from the vaccine developer, Vaxart, and the nonprofit clinical research organization, the Lovelace Biomedical Research Institute – tested a vaccine candidate that uses adenovirus as a vector to express the SARS-CoV-2 spike protein. The human vaccine is intended to be taken as a pill.
In studies using hamsters, the vaccine caused a strong response to antibodies in the blood and lungs. When the animals were exposed to high levels of the SARS-CoV-2 virus, which caused sudden infections, they were less symptomatic than unvaccinated hamsters and had lower levels of infectious virus in the nose and lungs. As a result, they do not shed as much virus through normal air exposure.
Unlike vaccines that are injected into a muscle, Langel said, mucosal immunizations increase the production of immunoglobulin A (IgA) – the first line of defense for the immune system against pathogens – in the nose and lungs. These mucosal entry ports are then protected, making vaccinated less likely to transmit an infectious virus during sneezing or coughing.
“Our data show that mucosal immunization is a viable strategy to reduce the spread of COVID by airborne transmission,” Langel said.
Langel said the study focuses on the original SARS-CoV-2 virus and new studies will be created to test the vaccine against Omicron variants.
In addition to Langel, the study’s authors include Susan Johnson, Clarissa I. Martinez, Sarah N. Tejacusuma, Nadine Peinovich, Emery G. Dora, Philip J. Quell, Hamad Irshad, Edward G. Barrett, Adam Verts and Sean N. Tucker.
reference: Langel SN, Johnson S, Martinez CI et al. SARS-CoV-2 type 5 adenovirus vaccines are delivered orally or intranasally, reducing the severity and transmission of the disease in a hamster model. Science Transl Med. 2022. doi: 10.1126 / scitranslmed.abn6868
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