NIAID Now | December 08, 2021
Colorized scanning electron micrograph of a cell (green) infected with a variant strain of SARS-CoV-2 virus particles (purple), isolated from a patient sample. Image captured at the NIAID Integrated Research Facility in Fort Detrick, Maryland.
COVID-19 Single-Dose Nasal Vaccine Designed for Infants, Children
Candidate Vaccine Against HPIV3 and SARS-CoV-2
NIAID scientists have developed a candidate COVID-19 vaccine targeted for infants and young children that would require one dose delivered by a nasal spray. They originally had been working on a vaccine to prevent respiratory disease caused by human parainfluenza virus type 3 (HPIV3) in young children. When the COVID-19 pandemic began, they quickly adapted their project to include SARS-CoV-2, the virus that causes COVID-19. A pediatric clinical trial is being planned for a single vaccine that would protect against both viruses.
In a new study published Dec. 7 in PNAS, NIAID’s Ursula Buchholz, Ph.D., Shirin Munir, Ph.D., Cyril Le Nouen, Ph.D., and colleagues in Bethesda, Maryland, and Hamilton, Montana, describe how they used a weakened version of a bovine/human parainfluenza virus (called B/HPIV3) to deliver SARS-CoV-2 spike protein to stimulate immunity against COVID-19. Think of how we use a grocery cart to carry food items to our vehicles. In this case, B/HPIV3 is the cart loaded with protective proteins that train our immune system to protect against SARS-CoV-2 and HPIV3. The vaccine is noteworthy because the nasal delivery creates immunity in the respiratory tract, which is thought to be particularly effective in restricting respiratory virus infection and transmission.
The group developed two versions of the vaccine for SARS-CoV-2 and compared them in hamsters to mimic COVID-19 in people. Candidate vaccine B/HPIV3/S-2P performed the best and was safe and effective at preventing SARS-CoV-2 from spreading in the nose and lungs.
SARS-CoV-2 and COVID-19 need no introduction. HPIV3 causes respiratory illness in infants and young children. There are four types of HPIVs, which commonly cause upper and lower respiratory illness in infants, young children, older adults, and people with weakened immune system. There is no vaccine or treatment for HPIVs; most people recover on their own, but disease can progress to serious conditions like bronchitis and pneumonia. Among the PIVs, HPIV3 is responsible for the greatest burden of disease.
Of interest, the scientists say the B/HPIV3 vaccine platform likely would have reduced effectiveness in older people because by about age 5 almost everyone has been exposed to HPIV3 and has developed immunity. Thus, the weakened B/HPIV3 virus vaccine is designed for use in young children to protect against HPIV3 and COVID-19.
Reference: X Liu, et al. A single intranasal dose of a live-attenuated parainfluenza virus-vectored SARS-CoV-2 vaccine is protective in hamsters. PNAS DOI: https://doi.org/10.1073/pnas.2109744118 (2021).