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New research suggests a groundbreaking approach in the fight against COVID-19: administering the vaccine directly to the respiratory tract, the primary entry point for SARS-CoV-2 infection, may significantly boost protection against the disease. The study, conducted in monkeys, highlights the potential of this novel method to strengthen immunity against COVID-19.
While acknowledging the remarkable success of the global COVID-19 vaccination campaign, which has saved an estimated 20 million lives, researchers highlighted a limitation of current vaccines. Although these vaccines offer defense against severe disease, they fall short in preventing infection and transmission.
According to Dan H. Barouch, the corresponding author of the study from Beth Israel Deaconess Medical Center (BIDMC), US, the failure of existing SARS-CoV-2 vaccines, delivered via intramuscular injection, to prevent infection might be due to their inability to generate robust mucosal immune responses at the entry point.
The study, published in Nature, demonstrated that innovative immunization strategies significantly enhance mucosal immunity in non-human primates, amplifying protective efficacy against mucosal virus challenges, such as SARS-CoV-2.
In the research, 40 adult rhesus macaques were initially primed with the Ad26 COVID-19 vaccine, akin to the shots administered to adults. A year later, the monkeys received booster doses via various routes: intramuscular (IM), intranasal (IN) through nasal spray, intratracheal (IT) via nebulizer or inhaler, and an mRNA vaccine (Pfizer-BioNTech) via the IN route. Some monkeys received no boosters as a control group.
Upon challenging the monkeys with a high dose of the virus, the researchers analyzed their immune responses by sampling blood, nasal secretions, and lung fluids.
The findings revealed that the Ad26 booster administered through the IT route provided nearly complete protection against a high-dose SARS-CoV-2 challenge, eliciting superior mucosal immunity compared to IM or IN routes. However, mRNA IN boosting proved ineffective, suggesting the need for improved formulations for successful mucosal delivery of mRNA vaccines.
Dr. Barouch concluded that these findings underline the potential of novel immunization strategies to significantly enhance mucosal immunity, improving protection against mucosal virus challenges, a significant breakthrough in combating COVID-19.
