at least one of the following criteria: very fast breathing, low oxygen saturation (SpO 2 flow oxygen supplementation via nasal cannula or mechanical ventilation, ICU admission for >4 hours and/or failure to respond/unconscious. In this study, 3 711 pregnant individuals with uncomplicated, singleton pregnancies were randomised to the Abrysvo group and 3 709 to placebo. Vaccine efficacy (VE) was defined as the relative risk reduction of the endpoint in the Abrysvo group compared to the placebo group for infants born to pregnant individuals who received the assigned intervention.
At the primary analysis, there were two primary efficacy endpoints, assessed in parallel, severe RSV - positive medically attended LRTD and RSV-positive medically attended LRTD, occurring within 90, 120, 150 or 180 days after birth. Of the pregnant women who received Abrysvo, 65% were White, 20% were Black or African American and 29% were Hispanic/Latino. The median age was 29 years (range 16-45 years); 0.2% of participants were under 18 years of age and 4.3% were under 20 years of age. The median gestational age at vaccination was 31 weeks and 2 days (range 24 weeks and 0 days to 36 weeks and 4 days).
The median infant gestational age at birth was 39 weeks and 1 day (range 27 weeks and 3 days to 43 weeks and 6 days). Vaccine efficacy is presented in Tables 2 to 5.
Table 2 Vaccine efficacy of Abrysvo against severe medically attended LRTD caused by RSV in infants from birth through 6 months of age by active immunisation of pregnant individuals – Study 1 CI = confidence interval; VE = vaccine efficacy a 99.5% CI at 90 days; 97.58% CI at later intervals Table 3 Vaccine efficacy of Abrysvo against medically attended LRTD caused by RSV in infants from birth through 6 months of age by active immunisation of pregnant individuals - Study 1 CI = confidence interval; VE = vaccine efficacy a 99.5% CI at 90 days; 97.58% CI at later intervals 7 Time period Abrysvo Number of cases N=3 495 Placebo Number of cases N=3 480 VE % (CI)a 90 days 6 33 81.8 (40.6, 96.3) 120 days 12 46 73.9 (45.6, 88.8) 150 days 16 55 70.9 (44.5, 85.9) 180 days 19 62 69.4 (44.3, 84.1) Time period Abrysvo Number of cases N=3 495 Placebo Number of cases N=3 480 VE % (CI)a 90 days 24 56 57.1 (14.7, 79.8) 120 days 35 81 56.8 (31.2, 73.5) 150 days 47 99 52.5 (28.7, 68.9) 180 days 57 117 51.3 (29.4, 66.8)