A taxi is the sensible choice on a Sunday, with heavy luggage, or for three or four people; public transport is cheaper for a single weekday traveler. Lourdes station is about 1.5 km above the sanctuary, with city buses and taxis for the downhill stretch.
For older travelers Tarbes-Lourdes is easiest: small, step-free, and 20 minutes from the hotel. Airport assistance is requested from the airline at least 48 hours before the flight; the TL shuttle accepts reduced-mobility passengers by reservation.