Maternal Antibody Interference and Vaccination Gaps in Goat Kids: Implications for Peste des Petits Ruminants Eradication

Peste des Petits Ruminants (PPR) is an economically devastating transboundary viral disease of small ruminants across Africa, Asia, and the Middle East. Despite effective live attenuated vaccines and the FAO/WOAH global eradication campaign targeting 2030, recurrent outbreaks persist, particularly among young goats. A major underrecognized obstacle is maternal antibody (MA) interference in goat kids, which compromises early-life vaccination and creates hidden immunity gaps within vaccinated herds. Maternal antibodies, acquired exclusively via colostrum, provide temporary passive protection but can neutralize vaccine virus and reduce effective seroconversion. This creates a critical “window of susceptibility” (typically 2–5 months of age) during which goat kids are neither protected against field infection nor responsive to vaccination. Reported estimates vary from approximately 70–100 days to detectability for up to 6 months, depending on the endpoint, assay, and study population. Conventional serosurveillance overestimates herd immunity because seropositive goat kids with residual MAs are falsely classified as protected. Fixed-age mass vaccination campaigns thus fail to achieve effective immunity in the most vulnerable age group. Strategies to overcome MA interference include delayed primary vaccination, booster schedules, targeted immunization, intranasal vaccination, and recombinant vaccines. Major barriers include poor farmer awareness, inadequate cold-chain infrastructure, and transboundary animal movement. Rapid farm turnover represents a separate operational barrier that further complicates vaccination timing. Achieving PPR eradication by 2030 requires a paradigm shift toward age-specific immunity in goat kids. Age-stratified protocols, farmer education, standardized diagnostic thresholds, rapid pen-side MA tests, and longitudinal studies in underrepresented regions including Pakistan are urgently needed.