Flight Crew Last 90 Days 106; Flight Crew Type 22000
Situational Awareness; Time Pressure; Communication Breakdown
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Flight Crew Took Evasive Action
Human Factors; Staffing; Environment - Non Weather Related
We were at 4;000 feet on a vector to final about 15 southeast of ZZZ when a TA came up on TCAS on the nose co-altitude. Right after it came up we were given one more turn to join final for [Runway] XXL.  In the turn the TA became a descending RA and we complied per the maneuver's section in the QRH.  We descended about 800 feet and finished the turn at which time we were Clear of Conflict.  As we leveled the wings we saw the traffic go by our right wing a little high as they were still at 4;000 feet; appearing to be no more than a half mile away. It appeared to be a smaller GA aircraft but went by quickly.  We told ATC we descended for an RA; at which time he said to just maintain 3;000 feet.  He seemed unconcerned and asked no questions nor gave us any information.  We never received a Traffic Advisory call prior to the initial TA. The Controller was busy; but did not seem to be swamped. Maybe staffing as a result of COVID-19 is a factor.
Air carrier Captain reported a TA/RA on initial approach and believes ATC staffing may have contributed to the event.