Pope Francis will wear a blood-stained rope belt which belonged to Romero, who was murdered at the altar, as he leads the ceremony in front of some 60,000 pilgrims.
Archbishop Vigano said the pope knew for years about sexual misconduct by McCarrick with adult male seminarians but did nothing about it.
Vatican's statement stated that both abuse and its cover-up can no longer be tolerated.
Santiago Archbishop Ricardo Ezzati declined to answer questions about accusations he was involved in a cover-up.
A sweeping grand jury report released in August revealed credible allegations against more than 300 predator priests and identified over 1,000 victims of child sex abuse covered up for decades.
Archbishop Carlo Maria Vigano has gone into hiding since an 11-page statement in which he alleged the pope knew about sexual misconduct by an American cardinal and did nothing about it.
Philip Wilson, 67, allowed to serve his detention at home after an assessment by prison authorities due to a range of health issues faced by the former archbishop.
Chilean prosecutors in late July named Ezzati as a suspect in an investigation into claims that he and other clergy covered up child sexual abuse by members of the Catholic Church.
Wilson, who has maintained his innocence, stepped down as archbishop of Adelaide in South Australia state but refused to resign while he was appealing against his conviction.
Wilson, 67, the archbishop of Adelaide, was convicted in May of failing to disclose to police abuse by a priest, Father James Fletcher, after being told about it in 1976 by two victims.
Australian PM Turnbull called on Pope Francis to sack disgraced archbishop after he was convicted of covering up child sex abuse.
Philip Wilson, the 67-year-old archbishop of Adelaide, was found guilty in May of concealing abuse by notorious paedophile priest Jim Fletcher New South Wales state during the 1970s.
Newcastle Local Court magistrate Robert Stone found him guilty of concealing a serious indictable offence of another person.
His conviction is another headache for Pope Francis, whose papacy has been haunted by allegations of sex abuse among Catholic priests.
It says he is doing so on his own volition and not with the consent or blessing of the Church.
Magistrate Belinda Wallington will hand down her decision on whether to send Pell to trial on May 1.
Gaspar Romero lamented the fact that Óscar Romero's murderers were never brought to justice.
Archbishop Hyginus Kim Hee-joong says a sex scandal involving a priest who should honour the sacred value of celibacy 'is utterly disappointing and shameful'.