Intranasal ChAdOx1 nCoV-19/AZD1222 vaccination reduces viral shedding after SARS-CoV-2 D614G challenge in preclinical models

TLDR

ChAdOx1 nCoV‑19/AZD1222 is an approved adenovirus‑based vaccine for SARS‑CoV‑2 that is currently being deployed worldwide. The study aimed to determine whether intranasal administration of ChAdOx1 nCoV‑19 could reduce viral detection in nasal swabs following challenge with a SARS‑CoV‑2 D614G spike variant. Researchers delivered the vaccine intranasally to macaques and hamsters, then challenged the animals with the D614G SARS‑CoV‑2 strain to assess viral shedding and tissue infection. Intranasal vaccination significantly lowered viral RNA and infectious virus in nasal swabs and in lower respiratory tissues of both species, with no virus detected in lung tissue after challenge or contact exposure, suggesting a superior route for reducing transmission.

Abstract

ChAdOx1 nCoV-19/AZD1222 is an approved adenovirus-based vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) currently being deployed globally. Previous studies in rhesus macaques revealed that intramuscular vaccination with ChAdOx1 nCoV-19/AZD1222 provided protection against pneumonia but did not reduce shedding of SARS-CoV-2 from the upper respiratory tract. Here, we investigated whether intranasally administered ChAdOx1 nCoV-19 reduces detection of virus in nasal swabs after challenging vaccinated macaques and hamsters with SARS-CoV-2 carrying a D614G mutation in the spike protein. Viral loads in swabs obtained from intranasally vaccinated hamsters were decreased compared to control hamsters, and no viral RNA or infectious virus was found in lung tissue after a direct challenge or after direct contact with infected hamsters. Intranasal vaccination of rhesus macaques resulted in reduced virus concentrations in nasal swabs and a reduction in viral loads in bronchoalveolar lavage and lower respiratory tract tissue. Intranasal vaccination with ChAdOx1 nCoV-19/AZD1222 reduced virus concentrations in nasal swabs in two different SARS-CoV-2 animal models, warranting further investigation as a potential vaccination route for COVID-19 vaccines.