Hybrid immunity to SARS-CoV-2 during pregnancy provides more durable infant antibody responses compared to natural infection alone.

BACKGROUND: Hybrid immunity (infection plus vaccination) may increase maternally-derived SARS-CoV-2 antibody responses and durability vs. infection alone. METHODS: Prospective cohort of pregnant participants with prior SARS-CoV-2 infection (anti-nucleocapsid IgG+, RT-PCR + or antigen+) and their infants had blood collected in pregnancy, delivery/birth, and postpartum tested for anti-spike (anti-S) IgG and neutralizing antibodies (neutAb). RESULTS: Among 107 participants at enrollment, 40% were unvaccinated and 60% were vaccinated (received ≥1 dose); 102 had previous SARS-CoV-2 infection in pregnancy (median 19 weeks gestation); 5 were diagnosed just prior to prior to pregnancy (median 8 weeks). At delivery, fewer unvaccinated participants (87% anti-S IgG+, 86% neutAb) and their infants (86% anti-S IgG+, 75% neutAb) had anti-S IgG + or neutAb compared to vaccinated participants and their infants (100%, p ≤ 0.01 for all). By 3-6 months postpartum, 50% of infants of unvaccinated participants were anti-S IgG + and 14% had neutAb, vs. 100% among infants of vaccinated participants (all p < 0.01), with lower median antibody responses (anti-S IgG log10 1.95 vs. 3.84 AU/ml, p < 0.01; neutAb log10 1:1.34 vs. 1:3.20, p = 0.11). CONCLUSIONS: In pregnant people with prior SARS-CoV-2, vaccination before delivery provided more durable maternally-derived antibody responses than infection alone in infants through 6 months.

A population-based study of primary human herpesvirus 6 infection.

BACKGROUND: Serologic studies indicate that human herpesvirus 6 (HHV-6) infects 90 percent of children by two years of age. Little is known about the acquisition, virologic course, and clinical manifestations of HHV-6 infection. METHODS: We prospectively studied a cohort of 277 children from birth through the first two years of life to define the pattern of acquisition of HHV-6. The children's saliva was tested weekly for HHV-6 DNA with the use of the polymerase chain reaction. Parents maintained a daily log of signs and symptoms of illness in their children. RESULTS: Primary HHV-6 infection occurred in 130 children, with cumulative percentages of 40 percent by the age of 12 months and 77 percent by the age of 24 months. The peak age of acquisition was between 9 and 21 months. The acquisition of HHV-6 was associated with female sex (adjusted hazard ratio, 1.7; 95 percent confidence interval, 1.2 to 2.4) and having older siblings (adjusted hazard ratio, 2.1; 95 percent confidence interval, 1.4 to 2.9). Among 81 children with a well-defined time of acquisition of HHV-6, 93 percent had symptoms, and 38 percent were seen by a physician. None had seizures. As compared with children who had other illnesses, those with primary HHV-6 infection were more likely to have fever (P=0.003), fussiness (P=0.02), diarrhea (P=0.03), rash (P=0.003), and roseola (P=0.002) and were more likely to visit a physician (P=0.003). CONCLUSIONS: The acquisition of HHV-6 in infancy is usually symptomatic and often results in medical evaluation. Roseola occurs in a minority of patients, and febrile seizures are infrequently associated with primary HHV-6 infection. Older siblings appear to serve as a source of HHV-6 transmission.