Developmental and reproductive toxicity (DART) study of a novel SARS-CoV-2 tetravalent recombinant protein vaccine (SCTV01E) in rats

SCTV01E, a novel SARS-CoV-2 tetravalent protein vaccine containing recombinant spike proteins of Alpha (B.1.1.7), Beta (B.1.351), Delta (B.1.617.2) and Omicron BA.1 (B.1.1.529.1) variants and SCTVA02B adjuvant, has received Emergency Use Authorization (EUA) in China and the United Arab Emirates (UAE) as a next-generation COVID-19 vaccine. A comprehensive reproductive and developmental toxicity evaluation was conducted in Sprague-Dawley (SD) rats under Good Laboratory Practice (GLP) conditions. Maternal animals were intramuscularly injected with 1 × or 3 × the highest human dose every other week prior to mating, followed by booster immunizations during gestation and lactation periods. The main findings showed that SCTV01E vaccination elicited robust binding IgG and neutralizing antibody responses against all four target variants. While no vaccine-related adverse reproductive effects were observed in parental male or female rats, transient injection site reactions and slight, reversible reductions in body weight gain and food consumption were noted. Key developmental parameters were not affected, and postnatal evaluation revealed no evidence of embryo-fetal malformations, developmental delays, or functional impairments in offspring. These results suggest a favorable safety profile for SCTV01E and its possible suitability for clinical trials in humans of reproductive potential. Furthermore, the efficient transplacental and lactational transfer of maternal antibodies observed in animal models suggests a potential protection: direct immunization of mothers may confer passive immunity to both fetuses in utero and neonates during breastfeeding.