Armed soldiers and police are on patrol in the village where thousands will gather in the coming days.
The site in southern France is popular with Catholics who are looking for healing.
The number of visitors has increased this week as series of special outdoors Masses are held to mark the Feast of the Assumption, when it is claimed Jesus' mother Mary ascended into heaven.
French authorities had already been planning extra security for the event but concerns increased following the attack in Normandy which saw an elderly priest killed by extremists claiming allegiance to Islamic State.
Lourdes officials refused to cancel this year's pilgrimage despite the concerns.
Almost 300 extra security personnel have been drafted in, including mobile intervention teams, soldiers, bomb squads and dog units.