Respiratory Syncytial Virus Vaccination during Pregnancy and Effects in Infants

S.A. Madhi, F.P. Polack, P.A. Piedra, F.M. Munoz, A.A. Trenholme, E.A.F. Simões,
G.K. Swamy, S. Agrawal, K. Ahmed, A. August, A.H. Baqui, A. Calvert, J. Chen,
I. Cho, M.F. Cotton, C.L. Cutland, J.A. Englund, A. Fix, B. Gonik, L. Hammitt,
P.T. Heath, J.N. de Jesus, C.E. Jones, A. Khalil, D.W. Kimberlin, R. Libster,
C.J. Llapur, M. Lucero, G. Pérez Marc, H.S. Marshall, M.S. Masenya,
F. Martinón‑Torres, J.K. Meece, T.M. Nolan, A. Osman, K.P. Perrett, J.S. Plested,
P.C. Richmond, M.D. Snape, J.H. Shakib, V. Shinde, T. Stoney, D.N. Thomas,
A.T. Tita, M.W. Varner, M. Vatish, K. Vrbicky, J. Wen, K. Zaman, H.J. Zar,
G.M. Glenn, and L.F. Fries, for the Prepare Study Group*


Novavax shows an almost 40% reduction in medically significant RSV-associated LRTIs, in their phase 3 randomized controlled trial with the support of the Bill and Melinda Gates foundation. They recruited healthy pregnant women, at 28 weeks through 36 weeks of gestation, before the start of the RSV season. They were randomly assigned with an overall 2:1 ratio to receive a RSV fusion (F) protein nanoparticle vaccine or placebo. In total, 4636 women were enrolled. The vaccine was safe, with a percentage of infants with a RSV-associated, medically significant lower respiratory tract infection of 1.5% in the vaccine group versus 2.4% in the placebo group (vaccine efficacy was 39.4%). This difference was not sufficient according to FDA-required prespecified criteria of vaccine efficacy. Interestingly, in the vaccine group RSV-related hospitalisations and all-cause pneumonia were significantly reduced by 44% and approx. 50%, respectively. Adding to that, a higher vaccine efficacy was seen in low- or middle-income countries (LMIC), where prevention of RSV is most needed. An explanation for the differential effect in high income countries versus LMIC is still being sought. For now, the faith of the first safe and efficacious RSV vaccine remains uncertain.

Full article on PubMed