The Vaccine Conspiracy Beliefs Scale (VCBS) is a widely used measure of conspiracy beliefs about vaccines, but evidence of its validity and measurement invariance, especially in youth samples, is still largely missing. The present study examined VCBS scores' factor structure, measurement invariance, convergent and discriminant validity, and incremental predictive validity. A sample of 803 Serbian youths (age range 15-24; 59.2% females) was recruited for the study. A modified single-factor model of the VCBS was supported, and showed evidence of full scalar invariance across gender, age, vaccination status, and personal history of COVID-19. Evidence of the VCBS scores' convergent and discriminant validity was obtained by examining associations with general conspiracy beliefs, vaccination attitudes, vaccination knowledge, intentions to get vaccinated against COVID-19, paranoia worries, fear of injections and blood draws, importance of God, self-rated health, and self-rated family's financial situation. The VCBS scores predicted a unique variance in the intention to get vaccinated against COVID-19, over and above vaccination attitudes and vaccination knowledge. The results suggest that the VCBS is a valid measure of vaccine conspiracy beliefs in youth.
Keywords: Vaccine Conspiracy Beliefs Scale; conspiracy beliefs; measurement invariance; vaccination; validity; youth.