Adjuvanted subunit intranasal vaccine reduces SARS-CoV-2 onward transmission in hamsters

Yongjun Sui ^1,2* Swagata Kar ³ Bhavna Chawla ³ Tanya Hoang ² Yuankai Yu ⁴ Shannon M Wallace ² Hanne Andersen Elyard ³ Jay A Berzofsky ²

• ¹ National Cancer Institute (NIH), Rockville, United States
• ² National Institutes of Health (NIH), Bethesda, Maryland, United States
• ³ BIOQUAL, Inc., Rockville, Maryland, United States
• ⁴ Experimental Pathology Laboratories, Sterling, Virginia, United States

Most COVID-19 vaccine trials have focused on recipient protecIon, not protecIon of their contacts, a criIcal need. As a subunit intranasal COVID-19 vaccine reduced nasopharyngeal virus more than did an intramuscular (IM) vaccine, we hypothesized that this vaccine might reduce onward transmission to others. We vaccinated hamsters with either the IMadministrated licensed mRNA vaccine twice or one dose of mRNA IM followed by adjuvanted subunit intranasal vaccine. 24 hours ader SARS-CoV-2 challenge, these animals were housed with naïve recipients in a contactless chamber that allows airborne transmission. Onward airborne transmission was profoundly blocked: the donor and recipients of the intranasal vaccine-boosted group had lower oral and lung viral loads (VL), which correlated with mucosal ACE2 inhibiIon acIvity. Notably, in this head-to-head comparison of COVID-19 booster vaccines on SARS-CoV-2 onward transmission, we found that staIsIcally significant viral reducIon in the lung Issues and oral swabs was observed only in the intranasal S1 nanoparIcle vaccine-boosted group, but not in the systemic mRNA vaccine-boosted group, suggesIng the superior protecIon of this intranasal vaccine, which could act as an agracIve vaccine booster candidate to complement the current licensed systemic vaccines. Overall, our study strongly supports the use of the intranasal vaccine as a boost to protect not only the vaccinated person, but also people exposed to the vaccinated person, a key public health goal.