A single-dose amber codon carrying live attenuated vaccine elicits pan-sarbecovirus immunity and blocks SARS-CoV-2 transmission

Existing COVID-19 vaccines exhibit clear limitations against the continuous emergence of variants of concern (VoCs), as their efficacy is challenged by the cumulative mutations in the spike or its RBD, which is the primary antigenic target. In addition, the intramuscular route of administration is suboptimal for inducing robust mucosal immunity, which is an important factor for preventing infection and transmission in the respiratory tract. To overcome these hurdles, we developed a live attenuated mucosal vaccine by introducing amber stop codons into the accessory genome of SARS-CoV-2, resulting in a highly attenuated yet immunogenic phenotype. A single intranasal vaccination induced broad-spectrum neutralizing antibodies against diverse VoCs. A single dose of this live attenuated vaccine can confer near-sterile immunity in mice against a greater than tenfold lethal SARS-CoV-2 challenge, eliciting high levels of both mucosal and systemic antibodies. Critically, vaccine-mediated protection also extended to antigenetically distinct VoCs and even SARS-CoV. Furthermore, vaccinated and subsequently challenged cohorts failed to transmit the virus to naïve animals, demonstrating a complete block of onward transmission. These findings establish our candidate as a true pan-sarbecovirus mucosal vaccine, offering a promising strategy to provide broad immunity and will likely defend against future sarbecovirus-driven pandemics.