COVID-19 Booster Vaccine Enhances Mucosal Immunity

COVID-19 vaccine booster administered directly to the respiratory tract's mucosal site—the main point of entry for SARS-CoV-2 infection—improves the protection against COVID-19 infection among non-human primates. The study also revealed that the intra-tracheal route provided near complete protection and induced greater mucosal immunity than it did through intra-nasal and intra-muscular routes. These findings were published in the journal Nature by physician-scientists at Beth Israel Deaconess Medical Center (BIDMC) and colleagues (1^✔ ✔Trusted Source
Mucosal boosting enhances vaccine protection against SARS-CoV-2 in macaques

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Immunization Strategies for COVID-19 Booster Dose

The global COVID-19 vaccination campaign saved an estimated 20 million lives. However, while current COVID-19 vaccines protect against developing severe disease, they do little to prevent infection and transmission.

“The failure of the current generation of SARS-CoV-2 vaccines delivered by the intramuscular (IM) route to block infection likely relates to their inability to induce robust mucosal immune responses at the portal of entry,” said corresponding author Dan H. Barouch, MD, PhD, director of the Center for Vaccine and Virology Research at BIDMC.

“In this study, we demonstrated that novel immunization strategies can markedly increase mucosal immunity in nonhuman primates and improve protective efficacy against a mucosal virus challenge.”

Barouch and colleagues primed 40 adult rhesus macaques with the Ad26 COVID-19 vaccine (Janssen/Johnson & Johnson) administered intramuscularly (IM)--like a shot in the arm adults typically receive.

Approximately a year later, the animals received a booster. Three groups received either a dose of the Ad26 vaccine via the IM route, the intranasal (IN) route (delivered via nasal spray), or the intratracheal (IT) route (delivered by nebulizer or inhaler). A fourth group received a dose of the bivalent mRNA vaccine (Pfizer-BioNTech) by the IN route. A sham group received no boosters.

When the macaques were later challenged with a high dose of the virus, the investigators sampled the animals’ blood, nasal and lung fluids to monitor their immune responses. They found that the Ad26 booster administered via the IT route provided near complete protection against a high-dose SARS-CoV-2 challenge and induced greater mucosal immunity than it did via the IN or IM route.

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In contrast, mRNA IN boosting proved ineffective, suggesting that improved formulations will likely be required for effective mucosal delivery of mRNA vaccines.

Reference:

1. Mucosal boosting enhances vaccine protection against SARS-CoV-2 in macaques - (https://www.nature.com/articles/s41586-023-06951-3)

Source-Eurekalert