The findings point to the need for mRNA-1273 booster vaccination to sustain high-level and rapid protection in the lung and to enhance protection against mild infection in the upper airway.
Protection in lungs from Delta replication not observed until day 4 post-challenge.
Neutralizing responses to Delta are low to undetectable 1yr after mRNA-1273 vaccination.
National Institute of Allergy and Infectious Diseases (NIAID) scientists and colleagues studying the durability of the mRNA-1273 vaccine in the lungs of rhesus macaques have found that one-year after vaccination, protection against the SARS-CoV-2 Delta variant is present, though the response is delayed in the lung. They also found limited protection in the upper airway in the nasal tissue.
In their study, the scientists immunized the macaques using a two-dose regimen with mRNA 1273, four weeks apart. One year later they challenged the animals with the SARS-CoV-2 Delta variant, which has been the dominant cause of COVID-19 cases for the past several months. They found that the vaccine protected the lungs by day four, but the response was slow compared to prior studies where animals were challenged much closer to the time of vaccination.
The authors showed that antibody responses in the lung were increased shortly after challenge with Delta, suggesting this as the mechanism of protection. They also noted reduced SARS-CoV-2 antibodies in the blood and lungs of the animals’ immune systems 48 weeks after vaccination, highlighting the importance of boosting to sustain immunity and protection.