By Chioma Obinna For decades now, vaccination programmes in Nigeria have been making progress. But the advent of COVID-19 vaccines may be bringing back ugly years of vaccine hesitancy which experts fear may erode gains already made in routine immunisation. According to experts, vaccine hesitancy is a continuum between vaccine acceptance and refusal. Eligible Nigerians are either delaying or refusing COVID-19 vaccines, even after the World Health Organisation, WHO, has confirmed the safety and effectiveness against the dreaded virus. Sunday Vanguard reports that if left unaddressed, vaccine hesitancy will not only threaten COVID-19 response but prevent Nigeria from achieving herd immunity.